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Mic Kaczmarczik's Fender Information Mic Kaczmarczik's Fender Information This directory contains USENET articles Mic has saved about guitars, equipment, pickup, techniques, players, and so on. Mic has graciously granted permission to post the stuff on the JT30 page on the off chance that it might be useful in the context of Blues Harmonica. Mic is not responsible for the content, just the collection. He must have quite alot of free time. 1974-prices 08-Sep-1997 12:35 2k 3-Spring-Reverb-Tanks 02-Oct-1998 20:42 3k 3-Wire-Cord-installa..> 23-Jun-1998 21:12 7k 5R4-not-enough-current 10-Jan-1997 15:41 1k 5V4-in-BF-Deluxe 09-Jul-1997 19:06 2k 6550s-in-Super 01-Sep-1998 14:58 3k 68-Princeton-Rectifier 13-Feb-1997 21:16 3k 68-Super-Reverb 10-Sep-1996 11:20 3k 6L6-in-Champ-Again 22-Nov-1998 11:19 4k 6L6-in-Deluxe-LV 29-Sep-1997 09:25 3k 6L6-in-Deluxe-Reverb 10-Feb-2000 15:09 1k 6SC7-to-12AX7 28-Feb-1998 22:41 2k 6V6-In-6L6-Amp-Test 31-Jan-1997 10:31 6k 6V6-in-Showman-Test 01-Feb-1997 23:36 6k 6V6s-in-Super 01-Apr-1997 21:25 2k AA-vs-AB-763 19-Jun-1997 11:40 4k AA763-vs-AB763 07-Mar-1997 12:33 1k Alternative-Switches 20-Aug-1997 12:33 5k Bad-Fender-Mods 21-Sep-1996 20:09 6k Bandmaster-Cathode-Bias 17-Jun-1996 00:46 7k Bassman-10-info 07-Jan-1996 09:37 2k Bassman-Head-Running..> 05-Aug-1999 19:13 2k Beef-Up-Tweed-Champ 19-Nov-1997 22:41 2k Birth-of-Fender-Reverb 03-Jul-1996 11:08 2k Blackface-Cabinet-Dates 26-Feb-1996 14:02 2k Blackface-Pro 16-Jun-1995 13:52 1k Blame-UL 14-Jan-1997 10:43 4k Blues-Deluxe-review 24-Aug-1995 15:03 10k Brown-Bassman-Transf..> 16-Oct-1996 23:01 4k Brownface-Trem-Pulse 22-Aug-1998 00:59 1k Brownface-Tremolux-C..> 21-May-1997 20:44 2k CBS-Deluxe-Reverb-Ch..> 04-Jan-1998 00:42 2k Champ-8ohms 04-Sep-1995 17:14 11k Champ-Speakers 10-Apr-1995 16:06 1k Champ-Transformers 01-Mar-1999 22:16 2k Champ-problems 24-Jun-1995 21:03 3k Champ-speakers 15-May-1995 10:34 2k Choke-Specs 24-Dec-1996 08:44 2k Clean-Ckt-Board 26-May-2000 15:47 5k Concert-Head-Footswitch 27-Oct-1997 11:59 2k Dead-Amp-Checkout 04-Feb-1998 15:55 3k Deluxe-Cathode-Bias-Mod 21-May-1996 07:40 3k Deluxe-Tweed-vs-BF 13-Sep-2000 14:48 6k Deluxe-reissue-vs-or..> 01-May-1996 13:39 4k Design-Eras 01-Sep-1998 14:58 3k Detailed-AB568-test 11-Jan-1997 13:42 14k Dr-Z-Harp-Amp-Mods 07-Feb-1997 10:31 1k Early-Blackfacing 04-Sep-1998 13:03 2k Ed-Jahns-Xformers 09-Jan-1998 17:51 2k Eyelet-Board-Problems 21-Apr-1997 22:23 2k Faceplate-Restoration 24-May-1997 14:46 1k Factory-Mistakes 24-Oct-1996 10:10 1k Fender-6V6-Overvoltage 05-Aug-1994 09:54 2k Fender-AA568-circuit 27-Jul-1995 11:59 1k Fender-Alternative-F..> 20-Aug-1997 12:33 5k Fender-Amp-Covering 09-Oct-1994 10:51 2k Fender-Amp-Dating 04-Oct-1994 22:45 3k Fender-Amp-Tremolos 20-Nov-1995 13:18 4k Fender-BF-Bassman-mods 02-Mar-1995 11:57 6k Fender-BF-SF-changes 04-Feb-1996 17:46 3k Fender-Bias-Pot-Fail..> 20-Mar-1996 20:33 3k Fender-Bias-Schemes 12-Jul-1996 21:18 4k Fender-Blackface 09-Oct-1994 10:58 2k Fender-Blues-Deluxe-..> 11-Jan-1996 13:05 2k Fender-Cap-Replacements 05-Sep-1996 17:43 2k Fender-Channel-Coupl..> 11-May-1996 11:58 2k Fender-Combo-Reverb-..> 12-Jul-1995 13:42 1k Fender-Concert-Reissue 18-Dec-1994 21:18 3k Fender-Concert-Tremolo 09-Jan-1996 13:17 2k Fender-Correct-Tubes 18-Mar-1995 22:06 3k Fender-Deluxe-Power-..> 18-Apr-1996 12:08 1k Fender-Deluxe-reissue 16-Nov-1994 12:11 2k Fender-Ext-Spkr-Jack 25-Nov-1995 00:16 5k Fender-Grill-Cloth 04-Oct-1994 12:56 1k Fender-ID-circuits 24-Oct-1995 11:34 3k Fender-Input-Jacks 26-Mar-1996 14:36 2k Fender-Midrange-Knob 08-Mar-1993 13:34 1k Fender-Normal-Channel 30-May-1996 01:06 15k Fender-RI-Reverb-Tube 06-Sep-1996 10:34 1k Fender-RI-Reverb-Tweaks 27-Jul-1996 15:11 2k Fender-RI-Reverb-mods 31-Aug-1996 09:47 2k Fender-Reverb-Both-C..> 11-Jun-1996 21:47 3k Fender-Reverb-FX-loop 01-Jul-1996 00:29 4k Fender-Reverb-Reissue 16-Oct-1994 09:35 2k Fender-Reverb-Transf..> 13-Mar-1995 23:13 2k Fender-SF-vs-BF 07-Dec-1995 10:43 41k Fender-Silverface-facts 02-Jul-1995 21:51 2k Fender-Super-60-price 12-Feb-1995 16:12 2k Fender-Super-pricing 11-Oct-1994 09:40 2k Fender-SuperChamps 20-Nov-1994 13:53 2k Fender-The-Twin 05-Oct-1995 17:15 5k Fender-Tone-Circuit 29-Nov-1995 00:29 10k Fender-Tone-Circuits 02-Dec-1995 09:27 2k Fender-Transformer-C..> 13-Jan-1996 19:10 2k Fender-Treble-Caps 23-Jul-1996 23:41 2k Fender-Tube-Chart-Dates 24-May-1994 15:05 2k Fender-Vib-Rev-Pedal 23-Jan-1996 07:36 1k Fender-Vibrato-Ticking 23-Mar-1996 15:48 4k Fender-Vibro-King-ci..> 06-Aug-1994 10:19 3k Fender-VibroVerb 20-Mar-1995 10:09 2k Fender-Vibrolux-RI-r..> 11-May-1995 13:34 4k Fender-Was-Dumb 22-Apr-1997 12:50 3k Fender-amp-tremolo 31-Jan-1994 22:57 3k Fender-bad-Supers 02-Jul-1995 21:50 2k Fender-brownface-top..> 07-Oct-1995 21:13 3k Fender-coupling-caps 10-Jan-1996 11:09 3k Fender-decrease-reve..> 26-Apr-1995 16:01 3k Fender-diodes 26-Apr-1995 15:51 3k Fender-neg-feedback 21-Jul-1995 13:47 3k Fender-replacement-p..> 05-May-1995 14:32 1k Fender-speaker-recs 04-Oct-1995 12:11 1k Fender-tone-circuit-..> 28-Mar-1996 13:13 2k Fender-vibrato-pot 04-Oct-1995 12:07 3k Footswitch-specs 28-Dec-1996 09:37 1k Grid-Blocking 22-Jul-1997 12:01 11k Homebrew-Vibroverb 19-Jan-1995 11:17 2k Invert-normal-channel 13-Oct-1997 14:57 2k Knob-Changes 08-Aug-1998 20:47 2k More-Pro-Reverb 01-Oct-1995 10:59 4k Narrow-Deluxe-Chassis 01-Mar-1998 13:27 1k No-5R4s 05-Jan-1997 22:04 2k Normal-Channel-Delay 01-Apr-1997 21:27 1k PA-100 07-Jun-1997 08:18 1k Pot-Tapers 01-Feb-1997 11:11 2k Princeton-Adjustable..> 07-Feb-1999 16:15 5k Princeton-Mods 24-Nov-1996 14:29 5k Princeton-PI-Headroom 07-Dec-1996 10:10 1k Princeton-PI-Heater-..> 27-May-1998 19:30 2k Princeton-PI-Mod-Layout 12-Jul-1999 12:50 2k Princeton-Reverb-Power 19-Apr-1998 23:33 2k Princeton-Reverb-Tweaks 08-Jul-1999 19:44 4k Princeton-Vs-Deluxe 09-Jan-1996 13:20 3k Princeton-driver-mods 07-Jan-1997 10:28 6k Princeton-tone-bypass 14-Nov-1996 11:04 3k Princeton-with-5881s 21-Jan-1996 21:05 3k Pro-Reverb-History 10-Sep-1996 11:18 3k Pro-Reverb-Orig-Spea..> 27-Dec-1997 10:19 1k Pro-Reverb-Parts 29-Nov-1995 08:14 3k Pro-Reverb-Questions 02-Feb-1996 18:26 4k Pro-Reverb-Speakers 09-Feb-1996 20:16 2k Pro-Reverb-baffles 08-Oct-1995 22:32 1k Pro-with-a-15 13-Mar-1996 23:32 1k Proper-Blackfacing 19-Aug-1998 19:08 4k Pull-Boost-Failures 18-Nov-1996 19:18 1k RI-Bassman-Mods 04-Nov-1996 08:51 3k Red-Knob-Twin-problems 12-Sep-1997 15:02 3k Reduce-Champ-Screen-..> 05-May-2000 15:57 1k Replacing-Glued-Baffles 01-Jan-1998 12:01 4k Restoring-Grille-Cloth 25-Sep-1996 15:44 3k Reverb-Amp-Effects-Loop 24-Jun-1997 00:05 4k Reverb-Fixes 03-Oct-1998 13:04 2k Reverb-Pan-Bottom 22-Nov-1996 09:18 3k Reverb-Trans-Specs 24-Oct-1997 18:53 1k Reverb-Unit-Mods-Page 14-Jul-1999 23:29 1k Rivera-Designed-Fenders 09-Apr-1998 13:53 3k SF-Deluxe-Reverb-Que..> 01-Nov-1998 23:02 19k SF-Deluxe-mods 02-Oct-1996 19:09 3k SF-Reverb-Cathode-Re..> 03-Jun-1997 11:58 1k SF-Vibrolux-Changes 25-Apr-1997 23:40 2k Scrape-Vibrato-Pot 05-Feb-1997 11:05 5k Screen-Resistors 11-Nov-1996 20:44 2k Shielding-Plate-Prob..> 07-Feb-1999 16:16 3k Showman-vs-Twin 03-Dec-1995 10:51 1k Silverface-Changes 12-Jan-1998 09:45 5k Silverface-Pro-Reverbs 12-Jun-1995 10:28 1k Small-Trannys-Someti..> 19-Jan-1998 13:30 1k Super-112-schematic.gif 03-Mar-1998 10:56 235k Super-Champ-6C10 10-Oct-1998 10:25 1k Super-Molestation 28-Jun-1995 11:55 5k Super-Too-Much-Bass 04-Jun-1998 10:06 2k Tolex-Repairs 01-Jul-1998 15:55 3k Tremolo-Tick-Tips 26-May-1997 11:33 2k Tweed-Champ-Filter-Caps 10-Mar-1998 23:07 3k Tweed-Deluxe-Bypass-Cap 16-Sep-1998 18:11 1k Tweed-Deluxe-Transfo..> 07-Jan-1997 13:41 2k Tweed-Twins 10-Oct-1998 20:00 4k Twin-Reverb-History 12-Jan-1996 12:35 3k Twin-Reverb-Variants 29-Aug-1995 21:56 4k Twin-Reverb-overdrive 24-Aug-1996 16:04 3k Vibrato-Click-Fixes 11-Dec-1997 22:58 1k Vibrato-Tick-Svc-Bltn-9 26-Jan-1998 18:49 3k Vibro-King-fat-switch 22-Nov-1994 13:16 2k Vibro-King-info 18-Oct-1994 11:03 4k Vibroverb-tone 07-Jun-1995 13:13 2k What-Makes-Fender-Sound 16-Jul-1998 19:31 2k What-Was-Ice-Cube 05-Apr-1998 11:04 1k What-is-Hi-Pot 02-May-1998 23:37 2k Why-68K-Input-Resistors 01-Sep-1998 15:37 3k Why-No-More-Cloth-Wire 03-May-1999 11:25 2k Why-Silverface-Changes 01-Sep-1998 10:42 29k diy 06-Mar-1999 11:06 2k 1974 prices From [email protected] Mon Sep 8 12:35:26 CDT 1997 Article: 62903 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!worldnet.att.net!newsadm From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Info on Quad Reverb? Date: Mon, 08 Sep 1997 03:10:06 -0700 Organization: AT&T WorldNet Services Lines: 28 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: 207.116.40.103 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01Gold (Win95; I; 16bit) Xref: geraldo.cc.utexas.edu alt.guitar.amps:62903 Arne Olav Nygard wrote: > > I'm really looking for a Twin Reverb, but I've been offered to buy an > early seventies Quad Reverb head. Does anybody have any info on this > amp? How does it compare to the Twin Reverb? What will a good price be? > > - ao As of March 10,1974 the prices were listed at: Dual Showman Reverb with PS 15 $965.00 21-0130 with JBL's $905.00 21-0100 Quad Reverb $675.00 21-2300 with JBL's $965.00 21-2303 Super Six Reverb $650.00 21-2200 with JBL's $1147.00 21-2204 Vibrosonic Reverb with PS 15 $645.00 21-2800 with JBL's $615.00 21-2801 Twin Reverb Fender 12" $575.00 21-0200 with JBL's $720.00 21-0203 These were the prices back then. Check the price differences between the different models. The Fender PS (Professional Speakers) were made for Fender by Gauss and were rated at 200 watts RMS. I Hope this information helps you in some way. Regards, Rich Koerner, Time Electronics. http://home.att..net/~rich-karl 3 Spring Reverb Tanks From [email protected] Fri Oct 2 20:42:11 CDT 1998 Article: 130040 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!sunqbc.risq.qc.ca!nntp.flash.net!excalibur.flash.net!notfor-mail From: Danny Russell <*NOSPAM*[email protected]> Newsgroups: alt.guitar.amps Subject: Re: 2 vs 3 spring reverbs ? Date: Fri, 02 Oct 1998 18:32:30 -0700 Organization: ACME Lines: 36 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: p77.sas16.dialup.det1.flash.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win16; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:130040 Tremolux wrote: > > > However, if the driving > >and recovery circuit is optimized to the characteristic tank, it can be > >made to work alright. > > Can you elaborate on this "optimization"? BTW, I agree with your previous > remarks about the 3 spring tank. I tried one in my Twin and after about 10 > minutes I took it out and put the original tank back in. the 3 spring tank was > just too much. The big thunderous, obnoxious, long decay character is mostly in the low-end. The high end is on the other hand is quite nice, really smooth, and decays a little faster. The simplest thing to do for starters is to re-E.Q. an appropriate amount of bottom out on the return end. On a Fender, lessen the .003 coupling cap to some smaller value. For finer points, it would help to hammer the driving 12AT7 pair with a bit more upper signal to "jangle" up the 3-spring tank's character a bit 'cause it's almost too sugar-smooth. The only available change is to raise the 470 ohm shared Rk to 1k or 1.5k (which it probably should be anyway) then bypass with .22 or .47. Be alert for any oscillation razzing which can be cured by re-adjusting the position of those jumpers across the tube socket. The 12AT7 actually needs to be overdriven a bit too get a good splashy surf-boing. You can see where this is headed, just take it from here. P.S. I've gotten a fair amount of accutronics tanks lately that needed to have the piss shaken out of 'em to loosen up the dampers at both ends of the springs. The decay dampers are not always positioned squarely or something, and one of the springs will be way overdamped relative to the other(s), so what you end up getting is sort of a "Peavey" reverb sound. Shaking the tank straightens the dampers and collectively evens out the decay rate of the springs. Shake it fairly vigorously so that the springs bang side to side, but not so that they go stretching way out the bottom and break off. (Keep one hand over the bottom.) -Danny 3 Wire Cord installation From [email protected] Tue Jun 23 21:12:44 CDT 1998 Article: 111555 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.internetmci.com!206.63.63.70!nwnews.wa.com!brokaw.wa.com!news3.nwnexus.com!news.nas.com!mschway From: [email protected] (Mike Schway) Newsgroups: alt.guitar.amps Subject: Re: Change BF AC power cord to 3 prong [long] Date: Tue, 23 Jun 1998 17:52:57 +0000 Organization: Network Access Services, Inc. Lines: 117 Message-ID: References: <[email protected]> NNTP-Posting-Host: pm3-d45.nas.com X-Newsreader: MT-NewsWatcher 2.4.4 Xref: geraldo.cc.utexas.edu alt.guitar.amps:111555 In article <[email protected]>, [email protected] (Rich ) wrote: > What needs to be done to replace the power cord on a BF pro reverb to > grounded 3 prong? I got zapped again. Outside on a concrete floor. It > wasn't real bad but it was annoying. Flipped the ground switch and all > was OK, but wouldn't a true ground be better (and safer)? > Thanks. Yes, under nearly any conceivable instance, the cordset should be upgraded and the "death cap" removed. First the standard disclaimer: If you have to ask, you probably shouldn't be working inside a tube amp. There is in excess of 500VDC in places on a live chassis and if you don't know EXACTLY what you're doing, you can DIE!!!! A good tech probably will charge about $40-50 for the job (including parts), so if you're a little unsure, have it done professionally. The following procedure may seem overly complicated, but it's really necessary since in addition to using an ungrounded 2 wire plug, the old Fenders had the switch on one leg and the fuse on the other. If the neutural (white) wire were fused, should the fuse blow, you would still have lots of current, only it would travel through the green wire, not the white. Best have both fuse and switch on the hot (black-wire) leg. That said: Here's the best procedure (I assume you know how to solder). Also, these instructions assume the chassis is set up with the knobs toward you and the power stuff is on the right hand side, away from you. 1) purchase a 18g/3 wire cord set (type SJO or SJT) about 8-9 ft long. 16/3 is overkill and probably won't fit too easily in the old strain relief (or the convenience outlet lugs for that matter.) 2) Solder a ring-type terminal onto the green wire of the cord set. Get a couple of toothed lock washers of a size which can fit over one of the studs holding the power transformer in place. Tin the exposed ends of the black and white wires. 3) Clip out the old cordset from the "convenience outlet". Remove all traces of solder and cordset wire from the outlet terminals...you'll need the entire original insde diameter of the lug free for the rewiring. Don't try to unscrew the lugs...not necessary nor easy. Use a solder sucker and/or desoldering braid to remove the solder. 4) Remove the old cordset and strain relief by using pliers to compress the longer diameter of the strain relief and pull it out. Save the strain relief 'cause you'll need it later. 5) Unsolder the white/yellowish jumper from the power switch (leaving one black power transformer primary lead attached to the other terminal). Remove the fuse from the holder and unsolder both leads of the fuseholder. Unsolder all 3 terminals of the ground switch. Keep the wire...especially if it's the nice cotton-wrapped stuff...the longer pieces are good to use for the rewiring coming up. 6) Remove the "death cap" (.047uF/600V) attached to the wiper of the ground switch...lower right side lug. Clip the other end of the cap where it goes through the hole in the chassis. You probably would have a hard time actually desoldering it from the chassis, neatly clipping is ok. 7) Now it's time to rewire. Starting from the power switch and working toward the AC cordset: Using 20-22g unstranded wire, neatly run a jumper >from the unused lug of the power switch (the other lug has one power transformer primary attached) to the "ring" lug of the fuse holder. Keep wire runs neatly tucked inside the lip of the chassis. 8) Run another wire from the tip (innermost) lug of the fuseholder to one upper terminal of the ground switch (probably should be the right-hand side in order to make sure the other black PT primary will be long enough for step 10.) 9) Run still another lead from the ground sw right side lug from step 8 to the lug on the convenience outlet with a *brass-colored* screw. 10) Attach the other power transformer primary (black) to the left side lug of the grounding switch. Run a jumper from that (lefthand) lug to the convenience outlet lug with the *silver-colored* screw. 11) Strip about 4 inches of the power cordset outer insulation and neatly remove any paper or fiber wrapping. Insert the cordset through its chassis hole and attach the green wire ring terminal over the rear right stud holding the power transformer. Use a lockwasher above and below the ring terminal and top it all off with the original nut. Tighten securely. 12) If possible, twist the black and white cordset leads and solder the black cordset lead to the convenience outlet terminal with the brass screw, attach the white wire to the silver-screwed terminal. Make sure you don't have too much exposed wire between the end of the insulation and the solder terminal here...it's really pretty easy to short across to the other 120V leg. 13) Secure the cordset to the chassis with the strain relief. If the new wire is much thicker than the old, you may have to hog out the inside of the strain relief with a rattail file. 14) Inspect all work, make sure wire ends are neatly clipped and all residue removed from the chassis (it's all too easy to inadvertently damage the insulation on the existing wiring by slipping with the iron...you'll have to repair *any* insulation burns with heat-shrink tubing), replace the fuse and speaker, hold your breath and power up. Note: if you follow these instructions, you'll still have the appearance of the ground switch but it won't be functioning. No problem as long as the venue you're playing is wired to code. Always try to use a 3-prong outlet, and if it ABSOLUTELY HAS to be a 2 prong outlet, use a "cheater" adaptor on your cordset and DON'T under ANY circumstance defeat the polarity of the cheater by filing down a prong (note that one prong is wider than the other). Good luck and work safely! --Mike Schway ===================================================================== Mike Schway | [visualize your favorite quote here] [email protected] | ===================================================================== 5R4 not enough current From [email protected] Fri Jan 10 15:41:01 CST 1997 Article: 33869 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!feed1.news.erols.com!news.bbnplanet.com!cpknews-hub1.bbnplanet.com!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: 5R4 vs. 5AR4/GZ34 Date: 10 Jan 1997 06:39:10 GMT Organization: AOL http://www.aol.com Lines: 18 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] >>>the 5R4 might not be so bad after all and can supply about 250 ma. at 600 volts dc , Like I said, there's nothing WRONG with the 5R4, it's just that it was designed for much higher voltage applications, and lower current than a 5U4. Fender amps run in the mid 400s for Voltage, so there is no need for the 5R4s higher voltage capability. At high current levels, the forward conduction drop through a 5R4 would be high. Considerably higher than a 5AR4. I never recommended trying to use a 5AR4 at the voltages you'd use a 5R4 at, it would be foolish to do so. Regarding the 5R4's ratings, my Sylvania Tube Manual says with a capacitor input filter, it's good for 150 ma. The 5U4 is rated at 275 ma. Bottom line is that if you have a Fender, use a 5U4 or 5AR4, not a 5R4. 5V4 in BF Deluxe From [email protected] Wed Jul 9 19:06:12 CDT 1997 Article: 55813 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!newspeer.sprintlink.net!news.sprintlink.net!Sprint!howland.erols.net!netnews.com!newsxfer.netaxs.com!ddsw1!news.mcs.net!not-for-mail From: "Teleologist" Newsgroups: alt.guitar.amps Subject: Re: 5U4 in BF Deluxe Reverb Date: 9 Jul 1997 22:38:33 GMT Organization: MCSNet Services Lines: 15 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: ctt-fw.ctt.com X-Newsreader: Microsoft Internet News 4.70.1155 Xref: geraldo.cc.utexas.edu alt.guitar.amps:55813 Simply Steve wrote in article <[email protected]>... > I've used a 5U4 in my SF Deluxe with no problems. It seems to add more > warmth to overall sound of the amp (which I like) but the sound > difference is not all that much. Nothing has blown up yet. > SF Deluxe Reverbs starting with the AB868 circuit came with 5U4GBs, so there should be no problem at all with these. Whether the transformer was changed >from the GZ34 A_764 BF amps to handle the extra current or had enough extra capacity is the big unknown. In a BF DR the 5V4 may be a better choice. Another option is a quality NOS 5Y3 in series with 2 diodes on the AC side these will take over should the 5Y3 short out, although the voltages will go up significantly. 6550s in Super From [email protected] Mon Aug 31 09:15:57 CDT 1998 Article: 124189 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: 6L6 Alternatives Date: 31 Aug 1998 05:21:59 GMT Organization: ICGNetcom Lines: 65 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: den-co71-103.ix.netcom.com X-NETCOM-Date: Sun Aug 30 10:21:59 PM PDT 1998 Xref: geraldo.cc.utexas.edu alt.guitar.amps:124189 In <[email protected]> [email protected] (TimTube) writes: > >In article , [email protected] (Jim >Kroger) writes: > >>> >>> The 6550s are going to draw about the same heater current as the EL34. They >>> will probaby sound pretty anemic at 30ma...Something around 45ma should be >>> about right. I've not put these in a ressue Bassman, but 6550s are my >>favorite >>> choice for getting incredibly big spank out of a Super Reverb. >>> >> >> >>Is this something that can be tried without modding or hurting the Super >>Reverb? >> >> >> >I should have added to that post that while I've not experienced power >transformer problems running 6550s in a Super Reverb, the 6550s do draw almost >twice the filament current of a 6L6...If the thought of melting your PT causes >anguish and trauma, I would suggest an auxiliarly filament transformer. > >Tim > >A great amp can make a lousy guitar sound great. >A lousy amp will make a great guitar sound lousy. > Lord Valve Speaketh: I've seen 'em done both ways...I know a dude who's been running 6550s in his BF Super Reverb for more than 20 years, on the stock tranny. If you do decide to use an auxilliary filament tranny, don't bolt it down to the chassis right away; run some long wires from it around the back of the chassis, power it up while the chassis is on the bench in front of you, turn it up pretty loud, and experiment with moving the tranny around so you can see what effect it has on the hum level. Once you have it located in a place where you get the least hum, draw lines around the feet with a Sharpie marker and mark the holes. You may not be able to put a bolt through all of the mounting feet because of stuff located inside the chassis, but you should try to mount it with all four if you possibly can. Another way to go is to mount it to the wall of the amp somewhere, and connect the wires with a Molex. Lord Valve Visit my website: http://www.freeyellow.com/members2/lord-valve/ Good tube FAQ for newbies. Click the e-mail link and request a tube catalog. I specialize in top quality HAND-SELECTED NOS and current-production vacuum tubes. Good prices, fast service. "I got the chop...I'll never get popped." - Tower of Power 68 Princeton Rectifier From [email protected] Thu Feb 13 21:16:05 CST 1997 Article: 38537 of alt.guitar.amps Newsgroups: alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!ix.netcom.com!rfries From: [email protected] (Robert Fries) Subject: Re: 68 Princeton Reverb Message-ID: Sender: [email protected] Organization: Netcom On-Line Services X-Newsreader: Forte Free Agent 1.0.82 References: <[email protected]> Date: Fri, 14 Feb 1997 02:09:31 GMT Lines: 77 Joe Rella wrote: >Robert Fries wrote: >> >> [email protected] (Robert Fries) wrote: >> >> >I just got one of these, tube chart says AA764. >> >> >The earliest schematic in the Weber and Pittman books is >> >AA1164. >> >> >Anybody got a schematic for AA764, or know the difference, if any? >> >> >RF >> >> In a breech of net etiquette, I'll follow up my own post... >> >> My AA764 tube chart calls for a GZ34 rectifier, the AA1164 schematic shows >> a 5U4; I suppose this might be the main (only?) difference. >> >> RF >> ***************** >> Robert Fries >> 415-988-9475 >> [email protected] >> ***************** >Robert, go with the 5U4GB. The main reason is the GZ34 will drive your >plate voltages up past 460V! Absolutely kills the 6V6GT's in no time. >I recently picked up a fairly clean '66 Princeton Reverb with the same >AA764 chart, and there was a GZ34 in there. I tested all the tubes and >discovered the Sylvania 6V6's were weak, but not quite dead yet. They >looked fairly new (nude base variety) Popped in a matched set of similar >Sylvania 6V6GT's and the vibrato turned very weak. Since that works off >the bias, I decided to start taking a few measurements, and discovered >the plate voltages were around 463V. Popped in a new 5U4GB, measured >again, and was down to 418V, with that nice strong vibrato. I surmise >that the reason for the quick 4 month run from AA764 to AA1164 was the >choice of rectifier tube for the above reason. Joe, You got me curious, so I experimented with various rectifiers: (this table reads best with a fixed-pitch font.) Rectifier Plate V Bias V Idle ma Power Line v Mesa 5AR4/GZ34 401 -29.4 23/25.5 17w 120.7 RCA 5U4GB (old) 389 -29.5 20.3/22.3 13.1 121 Nat'l Elec. 5AR4 (old) 378 -29.6 17.3/19.0 10.2w 121.5 Svetlana 5U4G(near new) 388 -29.4 19/21.7 12.25 121.3 GT SS 411 -29.5 25.3/28.3 18.6 121 The plate current measurements are in left tube/right tube form. The power measurements were taken using a 1khz sine wave, measure the P-P voltage with a 'scope, and use the formula P = (Vp-p^2)/8*R, into an 8 ohm 50 watt resistive load, which yields RMS power in watts. It seems my '68 puts out a lot less voltage than your '66. Worst case idle plate dissipation is with the SS rectifier, and at 11 watts, even that should be OK with the old RCA 6V6GTA's that are in there. I think I'll stick with the Mesa 5AR4/GZ34. All the above measurements were made with all tubes installed; when I checked the voltage with the SS rectifier and NO power tubes, I measured about 460V at the plate pins on the sockets. Did you have tubes installed when you did your measurements? Comments? RF ***************** Robert Fries 415-988-9475 [email protected] ***************** 68 Super Reverb From [email protected] Tue Sep 10 11:19:34 CDT 1996 Article: 22389 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!www.nntp.primenet.com!nntp.primenet.com!news.sgi.com!newspeer.gsl.net!news.gsl.net!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Opinion: 68 Fender Super Reverb Date: 10 Sep 1996 01:12:57 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 13 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com >>> It won'te be IDENTICAL because the transformers are different on blackface. Changing the phase inverter circuits will get you closer to the blackface sound. I did it to my Bandmaster Reverb and it improved the tone. William Allan Whittaker, Jr. wrote: Lee, have you ever personally dug into a 68? I have. They use the same lead dress, same cloth wire, same GZ34 rectifier, same blue tubular caps and same transformers as a 67. The only difference is that shitty phase inverter change and half-assed bias approach on the 6L6s. Rip that shit outta there and you have an electrical blackface. The other difference is they went to the Oxford ceramic magnet speakers. IMO, the CTS alnicos in the 67 sound better. From [email protected] Tue Sep 10 11:20:10 CDT 1996 Article: 22411 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntp.primenet.com!newspeer.gsl.net!news.gsl.net!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: Opinion: 68 Fender Super Reverb Date: 10 Sep 1996 04:27:27 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 18 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: newsbf02.mail.aol.com X-Newsreader: AOL Offline Reader In article <[email protected]>, [email protected](William Allan Whittaker, Jr.) writes: >>>>Regardless of the price, a 68 is a good investment...you can have a >tech change the bias and phase-inverter circuits BACK to what they were >before the CBS assholes got ahold of the company, and then you'll have >an amp that is IDENTICAL to a blackface Super. Some are already identical to a BF and some have the worst of the worst stuff, even though the tube chart is for an AB763. I've seen 2 from Dec. 1968 that had 2 .01mf disc caps wired together in parallel in all the places that you would find the blue tubular .02 mf caps. Apparently they ran out of them that week and had to improvised. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. 6L6 in Champ Again From [email protected] Sun Nov 22 11:19:40 CST 1998 Article: 140490 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: 6L6 in Champ Date: 22 Nov 1998 08:26:48 GMT Organization: ICGNetcom Lines: 68 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: den-co66-51.ix.netcom.com X-NETCOM-Date: Sun Nov 22 2:26:48 AM CST 1998 Xref: geraldo.cc.utexas.edu alt.guitar.amps:140490 In <[email protected]> [email protected] (Risehigh) writes: > >[email protected] wrote: ><do this >the other way around. >> > >caramba!! >i'm no expert (see my o-scope leads help post) >but my understanding is that you'll fry the 6V6's >if you put them in a 6L6 amp! >gurus?? >risehigh Lord Valve Speaketh: Depends on the plate voltage. You'd need to change the screen resistors to 1K/5W, too. Chinese or Russian 6V6s don't stand a chance in this application, but if you use some good NOS and the plate voltage is less than 450, you might get away with it. I don't do it, though. (Rumor has it that this mod only works well above the 49th parallel...) As for putting 6L6s where a 6V6 goes, I do *that* all the time, in Fenders. This question pops up like clockwork about every two months; on the one hand, you usually have the spec-book jockeys raving about the filament current being twice as much as the winding is rated at (it ain't; a little logical analysis makes this crystal clear, but few of 'em are willing to take the time to do so) and so on, while on the other hand we have cats like me (and trem, timtube, etc.) who've been doing it for years with no tranny failures. The rated filament current for a 6V6 is 450 mA; the rating on the 6L6 is 900 mA. When you first look at those figures, you think "uh-oh, twice as much, don't do it..." but you need to take into account the fact that the filament winding feeds *all* the tubes in the amp, as well as the pilot light. For a Deluxe Reverb, for instance, we have 4-12AX7s, 2-12AT7s, and 1-#47 lamp, besides the power tubes. At 300 mA per preamp tube, 150 mA for the pilot lamp, and 450 mA for each 6V6, this gives a total burden on the filament winding of 2.85 amps. (The rectifier tube has its own winding; more on that in a moment.) Using a pair of 6L6s increases this to 3.75 amps, which is only a 32% increase...not anywhere near twice, see? The filament winding can easily deal with the increase, but if you're worried about it, you can pull the #1 (Normal channel) preamp tube. You could also pull the #5 tube if you don't use the tremelo. This knocks the current back to 3.15 amps, a measly 11% over the stock value. You could even pull the pilot lamp, and get down to 3 amps...only 5% over. If you go to a solid-state rectifier, you remove the load from the 5V recto heater winding, and this lowers the PT's core temp, which is beneficial. Using the SS recto will increase the plate voltage too, which goes nicely with the 6L6s. I've set up a lot of Deluxe reverbs this way over the years, and I can't recall even one of them frying a power tranny. Other amps may not be quite as robust, but Fenders can do this with ease. Lord Valve Visit my website: http://www.freeyellow.com/members2/lord-valve/ Good tube FAQ for newbies. Click the e-mail link and request a tube catalog. I specialize in top quality HAND-SELECTED NOS and current-production vacuum tubes. Good prices, fast service. TONS of gear and parts in stock...let's DEAL! "I'm not an asshole, but I *play* one on the Internet." - Lord Valve 6L6 in Deluxe LV From [email protected] Mon Sep 29 09:25:33 CDT 1997 Article: 65316 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!iag.net!news.sgi.com!howland.erols.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: Lord Valve: Real or Not? Date: 29 Sep 1997 06:50:31 GMT Organization: Netcom Lines: 25 Message-ID: <[email protected]> References: <[email protected]> <01bccc74$1e59b740$0a169a8e@joth> NNTP-Posting-Host: den-co5-07.ix.netcom.com X-NETCOM-Date: Mon Sep 29 1:50:31 AM CDT 1997 Xref: geraldo.cc.utexas.edu alt.guitar.amps:65316 In <01bccc74$1e59b740$0a169a8e@joth> "joth" writes: > >hey hey hey,i thought 6l6's in a DR was NOT allowed! >LV please clarify this for me cause i wanted more headroom in my 68 DR and >i was told 6l6's werent an option. >i did all the recapping etc. and it sounds great and theres no hum but i >would like to try some 6l6's. > >thanks > Lord Valve Speaketh: You can put 6L6s into a DR...but NOT EL34s. The DR power tranny has no trouble with the extra filament current. If you're at all worried about it, you can pull the preamp tube from the Normal channel and also remove the tremolo tube. You can even pull the pilot bulb. You could also go to a SS rectifier...this will remove the load from the 5V recto heater winding, thus lowering the power tranny core temp. Some folks like the sound of 6L6s in a Deluxe Reverb, and some don't. This is a completely reversible mod (you may not have to do anything at all, other than rebias) and it's worth a listen. Lord Valve From [email protected] Mon Sep 29 09:25:50 CDT 1997 Article: 65277 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!iag.net!enews.sgi.com!EU.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!newsfeed.internetmci.com!206.72.192.13!news.albany.net!newsfeed.concentric.net!newsmaster!news From: [email protected] (Robert Fries) Newsgroups: alt.guitar.amps Subject: Re: Lord Valve: Real or Not? Date: Mon, 29 Sep 1997 07:01:49 GMT Organization: Concentric Internet Services Lines: 20 Message-ID: <[email protected]> References: <[email protected]> <01bccc74$1e59b740$0a169a8e@joth> NNTP-Posting-Host: ts024d13.cup-ca.concentric.net X-Newsreader: Forte Free Agent 1.11/32.235 Xref: geraldo.cc.utexas.edu alt.guitar.amps:65277 "joth" wrote: >hey hey hey,i thought 6l6's in a DR was NOT allowed! >LV please clarify this for me cause i wanted more headroom in my 68 DR and >i was told 6l6's werent an option. >i did all the recapping etc. and it sounds great and theres no hum but i >would like to try some 6l6's. 6L6 is definitely a possibility in a DR; lots of people do it. They do draw twice as much filament current, but the power transformer is (apparently) up to it. Don't expect an enormous difference - you may get a couple more watts, but the transformers just can't produce much more power. RF > Robert Fries 415-988-9475 r*f*r*i*e*s*@n*e*t*c*o*m*.com (remove the stars before e-mailing!) 6L6 in Deluxe Reverb From [email protected] Wed Jan 7 20:58:37 CST 1998 Article: 79224 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!newsfeed.direct.ca!portc01.blue.aol.com!audrey02.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Replacing 6V6 tubes in DR Date: 7 Jan 1998 21:28:21 GMT Lines: 11 Message-ID: <[email protected]> NNTP-Posting-Host: ladder02.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:79224 Disregard that hack O'Connor, hell, he's even advocated putting Sovtek 6V6s into 6L6 Fenders, shows how much that idiot knows. "TUT" my ass. More like "The Ultimate Hack". Now, with all that said, I would advise extreme caution in putting 6L6s into a 6V6 amp unless you're damn sure the power transformer can take the additional heater load. Now, in the specific case of a Fender Deluxe Reverb, YES, the power transformer can indeed take the additional load safely. I've been running the small-bottle 6L6s in my 64 DR for YEARS. No problems at all. I know several others who have done the same with identical results. Go for it, but remember that a rebias is essential. 6SC7 to 12AX7 From [email protected] Sat Feb 28 22:40:59 CST 1998 Article: 88325 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!Supernews73!supernews.com!Supernews69!not-formail From: [email protected] (Ned Carlson) Newsgroups: alt.guitar.amps Subject: Re: 6SC7 to !2AX7 Tweed conversion help WTD. Date: Sun, 01 Mar 1998 00:12:33 GMT Organization: Triode Electronics Lines: 52 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: [email protected] X-Trace: Supernews70 888711976 29643 (none) 206.141.208.123 X-Complaints-To: [email protected] X-Newsreader: Forte Free Agent 1.11/16.235 Xref: geraldo.cc.utexas.edu alt.guitar.amps:88325 On Fri, 27 Feb 1998 23:41:42 GMT, [email protected] (Bill Hatcher) wrote: >I want to swap one of the channels on my Tweed Pro to use a 12AX7 >instead of the 6SC7. Groove Tubes makes a product called a >"substitube" that is an 8pin male socket on one side and a nine pin >female on the other. Cost $40!!! Can someone tell me the wiring >diagram to make one of these out of an old octal base and a 9 pin >socket and some epoxy. You might consider picking up a tube manual for $14, it'll answer this and a lot of other questions... 12AX7 Pin Element 1 Plate 1 2 Grid 1 3 Cathode 1 4 Fil 5 Fil 6 Plate 2 7 Grid 2 8 Cathode 2 9 Fil Jump pins 4 & 5 Jump pins 3 & 8 6SC7 1 Shell ground 2 Plate 1 3 Grid 1 4 Grid 2 5 Plate 2 6 Cathodes 7 Fil 8 Fil You might like 12AY7 or 5751 in there better than 12AX7, a lot of folks do. Ned Carlson Triode Electronics,2225 W Roscoe St Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 "Worldwide Service, Neighborhood Prices" since 1985 Open 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun See our web site at http://www.triodeel.com Text file catalogs: Send a request to our Catalog 'Bot at [email protected] 6V6 In 6L6 Amp Test From [email protected] Fri Jan 31 10:31:02 CST 1997 Article: 36610 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!newspeer.sprintlink.net!howland.erols.net!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: 6L6 -> 6V6 mods Date: 31 Jan 1997 07:07:37 GMT Organization: Netcom Lines: 104 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: den-co5-24.ix.netcom.com X-NETCOM-Date: Thu Jan 30 11:07:37 PM PST 1997 In <[email protected]> [email protected] (Hamish Hubbard) writes: > >I'm feeling really motivated at the moment, so I'm going to attempt to >take this 'discussion' and turn it into a piece of useful knowledge. > >On one side we have Lord Valve, Tremolux, etc who theorize that running >6V6 tubes at 400 to 450V will toast them. >Evidence: >The design-maximum plate voltage for a 6V6GT is about 350V (from memory). >No empirical evidence that I am aware of (...if you're think they're going >to blow, why try it to be sure, I guess.) > > >On the other side we have K.O. who believes this is no problem. >Evidence: >Empirical evidence dating back to the '70s that 'western' 6V6 and eastern-block >"6V6" operate OK for long periods of time at up to 450V B+ in amps designed >for 6L6 tubes. >No dis-satisfied customers with this mod (?) > >It should be noted that Mr. O'Connor and Mr. Valve share the exact opposite >positions on the subject of overloading the heater windings of old Fender >transformers, which is rather curious IMHO. > >Would either side care to make any additions? I think it's too soon for >anyone to take either side as fact, but right now the evidence is in >favour of Mr. O'Connor. Lord Valve Speaketh: I can speak (from experience) to the question of installing 6L6s in 6V6 type FENDER amplifiers...it works just fine. I've been doing it for years, and I can't recall anyone coming back with a fried power tranny. The Fender power transformer is very beefy. I have a customer who had his Super Reverb (BF) outfitted with 6550s (NOT by me, that one's not my style) back in 1973 (he says...I've only been servicing his gear since around 1984), and although the trans runs hotter than normal, he's been gigging with this amp for pushing 24 years on the same transformer. As to the other question...Sovtek 6V6s at plate voltages of 470 volts, and not one failure in 20 years (Mr O'Connor's words, I believe)...I don't see that happening. There have been posts upon posts to this NG by techs, amateurs, and engineers alike bemoaning the low quality of the Sovtek 6V6, and its propensity to self-destruct at the drop of a riff. And we're talking Champs, Deluxes, and Deluxe Reverbs here, NOT Twins. SO...just for fun, I dug up the last 6 Sovtek 6V6s I had in my shop...the ones left over from the dozen I had back when three customers in a row became VERY irate after their Deluxe Reverbs lasted less than a set and a half, after I retubed them with Sovtek 6V6s...and I shoved a pair into a BF Super Reverb. The bias was first set to max negative; the amp was turned on and allowed to warm up on standby for a generous 5 minutes. The incoming AC line was adjusted to 120 VAC exactly. Upon taking the amp off standby, the left-hand power tube put on a rather spectacular fireworks display, taking the screen resistor with it. The amp was immediately powered down, the dead tube removed, and the smoked resistor replaced. Another 6V6 was installed, and the same warmup proceedure was followed. This time, once the tubes warmed up, the amp was operated into a 2-ohm dummy load and the output monitored on the scope. Due to the max negative setting of the bias control, the wave was extremely notchy; I decreased the bias voltage as far as it would go (without modifying the bias circuit) but there wasn't enough range to remove the crossover notch from the output. The measured voltages at this point in the experiment were -45.5V bias, and +471.2 volts plate, with the screens slightly lower than the plates by a volt or so. I turned out the lights in my shop, and had a peek at the plates. It was necessary to do this in darkness, as the glass on a Sovtek 6V6 is coated with a black substance on the inside, making it very difficult to observe the plates. Large orange spots were visible on the plates of both tubes. As I reached for the standby switch to shut the amp down, the right-hand tube went south in a major way, again taking the screen resistor with it. I removed both tubes from the amp (which, by the way, were hot enough to make me get rid of 'em really fast, and I was wearing WELDING GLOVES, as I always do when pulling hot tubes) and installed two of the remaining three untried tubes. Again, the bias pot did not have sufficient range to remove the crossover notch from the output, and again the plates lit up. I had a customer of mine plug his Strat into the head and play it into the speakers in the cabinet. This time, the tubes fared a little better; it took 15 minutes of playing (softly at first, and then balls-to-the-wall at the end) to kill a tube. I will admit, when overdriven, it sounded pretty good. The clean tone was WAY glassy, though. Incidentally, RMS wattage measured across the test load worked out to 26.3 watts. A Chinese 5AR4 was used for the rectifier. The amp was completely stock in all respects. I have a feeling that if the bias voltage could have been taken low enough to produce a decent-looking output waveform, the tubes would have shorted out WAY faster than they did, or the glass would have melted. (Don't laugh...I've seen this, but usually only on 6550's in amps that were over-fused.) My conclusion: not in a Super Reverb, they won't. Somebody try it with a Twin Reverb and post the results. Trem? Lord Valve [email protected] (Fat Willie) 6V6 in Showman Test From [email protected] Sat Feb 1 23:36:15 CST 1997 Article: 36821 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!newspeer.sprintlink.net!howland.erols.net!newspump.sol.net!ddsw1!news.mcs.net!not-for-mail From: "Teleologist" Newsgroups: alt.guitar.amps Subject: Re: 6L6 -> 6V6 mods (The Test results) Date: 2 Feb 1997 03:35:20 GMT Organization: MCSNet Services Lines: 89 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <01bc0f77$1ed2af20$610258aa@alsnt> NNTP-Posting-Host: ctt-ext.ctt.com X-Newsreader: Microsoft Internet News 4.70.1155 Teleologist wrote in article <01bc0f77$1ed2af20$610258aa@alsnt>... >> Just so happens I've got an old(but healthy & stock) BF Dual Showman head, > 2 matched quartets of Russian firecrackers with the same match #'s(8 > matched tubes), an ample supply of flameproof screen resistors, some fuses > rated 1a lower than called for, & a Halon fire extinguisher! I'm planning > to do 'The Experiment' this weekend. > Did The Test! Disclaimer: The results won't stop any flame wars(didn't expect that), are somewhat inconclusive, and would be statistically insignificant anyway(1 amp, limited # of tubes). Conditions: I replaced the 27K resistor in the bias circuit with a 20K to provide better adjustment range. 4 new matched Phillips ECG 470 ohm FP screen resistors were installed - also replaced the 470 ohm resistor in bias circuit with a 470FP. All 8 new matched Sovtek 6V6GT tubes were tested in low voltage tube tester - one scraped for poor characteristics. The Test: After twice blowing up a tube & screen resistor trying to switch on B+ after a 5 min warmup @ 117VAC with maximum negative bias, I decided to start at -45V bias with the Variac set @ 110VAC & got the thing on. Twiddled' the bias & Variac gradually to 115VAC, 20ma/tube(combined plate & screen) - all tubes were within 1.2ma & plate voltage was around 455V. Played my Strat through it(stock Dual Showman bottom) for 15 minutes with volumes between 3 & 6. All 4 tubes had oval-shaped areas of moderate plate glow. After a short cooling off period, I put a signal generator, scope, & dummy load on it - raised AC to 117VAC & rebiased to 17ma/tube(combined plate & screen @ idle) - 465V+ plate/460V screen. Output power with volume on 8 was right around 50W. Crossover notch was minimal. Played it again for 15 minutes with volumes between 4 & 6 and ended with a 5 minute blast at 8(those poor neighbors)! Some plate glow was still present on the inner pair of tubes - outers were very faint. Switched to an 8 ohm speaker load(D120F in my DR) & played again for about 20 minutes with volumes between 4 & 6 - no plate glow!(but no blast on 8 either). I planned to raise the AC to 120, rebias strictly by the crossover notch method, & try again, but got interrupted by a 'Honey Do' errand. Two hours later at power up(old settings) one of the tubes had a grid/screen failure(short) and took out the 470 ohm bias circuit resistor(zero bias when this happens) - lost 3 tubes & 2 screen resistors before fuse blew amazing that 1 tube actually survived! Replaced all screen resistors - bias circuit resistors, cap, & diode. Put the 7581As back in it, biased it to 40ma, & all is as Leo intended! Sound: (Subjective) Stock, the BF Showman has a very clean preamp compared to BF amps with Reverb. With single coils, distortion doesn't start until 8 & with 7581As you don't get much at 10! So with 6V6GTs we're talkin all power tube distortion! At 115V/20ma the clean sound was bright but still acceptable I would describe it as sounding like a stock BF Pro Reverb. Distortion started at 5 & was crisper, crunchier, & more saturated than a Pro Reverb. Note definition was still good when playing chords - nice Keith Richards 'Stonesy' sound. At 117V/17ma the clean sound was too glassy & strident for me. Distortion was interesting though, saturated & bright - not quite a plexi Marshall but the Strat neck pickup tones were definitely getting interesting. At 8 there was a lot of compression as well. I normally like to play on the edge at lower settings and I found that the amp broke into distortion very quickly & was hard to control. Through the JBL in the DR, the attenuated bottom end made the amp seem even more strident. Conclusions: At bias settings with acceptable tone(to me anyway), I don't see how one could avoid glowing the plates. Had I gotten to 120VAC with even less idle current and a 4 ohm load, I think the glow would have been solved, but the amp would have been brighter still, and I question whether the screens could take that much voltage. Maybe the tone is a whole different story with some hot humbuckers, but in no way shape or form does it sound like a Deluxe Reverb - of course the Showman lacks the extra preamp stage & has much higher voltages throughout. With the same transformers as a Twin Reverb, but 2 less tubes to power the Showman is probably a worst case test amp. A couple of days ago I expected the 6V6s to produce a darker fatter distortion - the bright crunchy sound was a surprise - perhaps it was because of this amp's clean preamp. As for reliability, I'll let you be the judge! I did break open & dis-assemble one of the 6V6s that fried a screen. About a 1/4" of screen winding near the center of the assembly had vaporized! All that was left were little globs of melted metal on the plate & on the grid winding. These particular tubes were all from the early 90s & were packed in the dark blue/yellow boxes with all Russian lettering & '6V6GT' written on the ends by hand. 6V6s in Super From [email protected] Tue Apr 1 21:25:21 CST 1997 Article: 43817 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!worldnet.att.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!news-peer.gsl.net!newsstock.gsl.net!news.gsl.net!van1s03.cyberion.com!news From: O'Connor Newsgroups: alt.guitar.amps Subject: Re: 6V6's in a Super?? Date: Tue, 01 Apr 1997 03:30:40 -0800 Organization: London Power http://www.wwdc.com/~power/ Lines: 23 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: mp4-110.wwdc.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0 (Win16; I) To: JDBree Xref: geraldo.cc.utexas.edu alt.guitar.amps:43817 JDBree wrote: > > I have a '67 BF Super and I'm curious if it could be set up to run with > 6V6's. I would like to get more power stage distortion at less volume. Hi Jeff Although others may debate this: yes, you can use 6V6s in your Super. To assure reliability, you should replace the 470-2W screen resistors with 1k-5W. This allows the use of Sovteks and even Chinese versions. The 'V's will provide only about 15-20W with all four speakers connected, as the stock configuration is not an optimal load-- but they will work okay with the resistor change above. With two speakers disconnected, the load becomes "more optimal" for the 'V's, but they will still only produce about 20W. Reverting back to 6L6s or 5881s with the 1k-5Ws allows ALL grades of these tubes to operate more reliably and with a less strained tone (as my customers describe it). Have fun! Kevin O'Connor AA vs AB 763 Re: slow down everybody... --------------------------------------------------------[ Follow Ups ] [ Post Followup ] [ Vintage Guitar Bulletin Board - Amps ] --------------------------------------------------------Posted by Andy Ruhl on June 19, 1997 at 10:00:33: In Reply to: slow down everybody... posted by mark n on June 19, 1997 at 08:31:11: ::: :::: : : : : : I have a BF Fender Bandmaster that has the AB763 circuit. : : : : : I understand that other models of Fender amps can also have : : : : : an AB763 circuit. : : : : : Does the AB763 refer to the type of components and the way : : : : : they are assembled in the circuit? : : : : : I have the Tube Amp Book Vol.3 (by Aspen Pittman) but it : : : : : has only the Bandmaster AA763 circuit. What is the : : : : : different between AA763 and AB763? : : : : : Thanks for your response. : : : : Hello Renaldo, : : : : During the Fender Blackface era and on into the early Siverface days, they used two letters followed by the date for their model numbers. Thus a model would start with say AA763 which means "AA" for first revision of that design, "7" meaning July and "63" meaning 1963. Thus the AB763 of any particular model would be the next revision of the basic "763" model and so on. : : : : The only difference between the AA763 Bandmaster and the AB763 Bandmaster is that the AB763 model had 1.5K grid resistors added to the 6L6 output tubes. By the way, most of the AB763 models are very similar, although an AB763 Super-Reverb will be different than an AB763 Bandmaster for instance. : : : : I hope this helps! : : : : Regards, : : : : Evan : : : another change common to most (if not all) of the "AA763" to "AB763" versions involved changing one of the 100K plate resisitors in the inverster stage to 82K : : Wait a minute, don't AA models have a .033 cap in the tone stack, instead of a .047 on most of the AB's? I think that the Super Reverbs had a .022. Andy : ---->hold on!!!! let's get a few things back in perspective. first of all, as an earlier thread eluded to, a "super" ab763 is NOT the same amp as a "bandmaster" ab763. so first & foremost, any comparisson between aa & ab MUST be within the same frame design or the comparisson is meaningless. : andy, you are right, aa763 to ab763 SUPER's changed the tone stack cap values [among other changes], but this has nothing to do with a bandmaster & its revision from aa to ab. the orig. question was about circuit numbering [ not amp-specific, true], however the text was about renaldo's bandmaster. i don't want to be a pain in the ass here, but we run the risk of confusing renaldo when we start "mixing amps" : as for the bandmaster, the aa to ab revision had more than just the 1.5k resistors on the grids. other changes were..1.) cap value on the power supply was 2x60uF, changed to 2x70uF, 2.) resistors added to said caps... 2x220k, 3.) 100k changed to 82k on "top" plate of the inverter, 4.)bias resistor on inverter changed from 27k to 22k, 5.)bias resistor on "photo side" of vibrato tube changed from 56k to 100k. : sorry to get long winded here, but the thread seemed to be getting a bit confused IMHO. : ---->mark n Mark's right. I forgot that the original amp was a bandmaster. I'm out of town right now, so I don't have a book to go to. I know that my AA763 1x15 Pro has the .033 cap where the AB model has the .047. I think that the Deluxes did the exact same value swap. So I figured that they all had some kind of change here. Oops. Andy --------------------------------------------------------Follow Ups: --------------------------------------------------------Post a Followup Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: --------------------------------------------------------[ Follow Ups ] [ Post Followup ] [ Vintage Guitar Bulletin Board - Amps ] AA763 vs AB763 From [email protected] Fri Mar 7 12:33:40 CST 1997 Article: 41268 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newspump.sol.net!ddsw1!news.mcs.net!notfor-mail From: "Teleologist" Newsgroups: alt.guitar.amps Subject: Re: AA763 vs. AB763 Super Reverb Date: 7 Mar 1997 12:25:12 GMT Organization: MCSNet Services Lines: 18 Message-ID: <01bc2af3$297e3dd0$610258aa@alsnt> References: <[email protected]> NNTP-Posting-Host: ctt-ext.ctt.com X-Newsreader: Microsoft Internet News 4.70.1155 Matt wrote in article <[email protected]>... > OK, this is puzzlin' me. > > I have one of each of the above, and in both the schematics and the > amps themselves I notice a difference that I don't understand. > > The 6L6GC's in the AB763 each have a 1500 ohm resistor tied to their > grids, the AA doesn't. > Those are the grid-stopper resistors, one of the few changes which were added to the AB circuit. Their purpose is to stop parasitic oscillations which sometimes occur in the AA circuit. Some people claim they effect tone - I'm curious how do your 2 amps compare??? If you're having any problems with oscillation, or for your own peace of mind, you should add them. I'd personally leave 'em out as long as the amp is behaving. The other change on some AB model Fenders is different cap values in the tone stacks. Alternative Switches From [email protected] Wed Aug 20 12:33:26 CDT 1997 Article: 60740 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!howland.erols.net!infeed1.internetmci.com!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!newstf02.news.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] (Lektrkblus) Newsgroups: alt.guitar.amps Subject: Re: 64 DELUXE Foot Switch Help Date: 19 Aug 1997 21:51:17 GMT Lines: 22 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:60740 >Subject: 64 DELUXE Foot Switch Help >From: [email protected] (Tokaitele) >Date: 19 Aug 1997 19:39:49 GMT >Message-ID: <[email protected]> > >I just bought a 64 Blackface Deluxe. It sounds great but there is no >footswitch for the vibrato channel. If I put in an RCA jack and ground it >the vibrato works fine but this doesn't seem practical. Is there a way to >find a switch that works in radio shack or someplace? I'd appreciate any >help. Please copy me via email if you have good advice. [email protected] > > Carvin sells a dual footswitch for thier amps for about $20.00. This is less than the price of just the two switches. I believe it can be taken apart and modified. I'm going to get one for my Deluxe Reverb II and modifiy it to suit my needs. You can't beat the price, and you may find an ingenious use for the extra switch. Chuck. [email protected] From [email protected] Wed Aug 20 12:33:37 CDT 1997 Article: 60772 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer.sprintlink.net!news.sprintlink.net!Sprint!howland.erols.net!panix!news.panix.com!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps Subject: Re: 64 DELUXE Foot Switch Help Date: 20 Aug 1997 10:22:09 -0400 Organization: Panix Lines: 23 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix3.panix.com X-Newsposter: trn 4.0-test55 (26 Feb 97) Xref: geraldo.cc.utexas.edu alt.guitar.amps:60772 Tokaitele wrote: >I just bought a 64 Blackface Deluxe. It sounds great but there is no >footswitch for the vibrato channel. If I put in an RCA jack and ground it >the vibrato works fine but this doesn't seem practical. Is there a way to >find a switch that works in radio shack or someplace? I'd appreciate any >help. Please copy me via email if you have good advice. [email protected] Any Fender dealer can get it for you (Mojo dealers stock 'em too). You'll have to cut off the 1/4" plug and solder in a phono plug. It'll cost around $35. Alternately, Yamaha dealers have a one button footswitch for around $10. It doesn't look like the Fender but if appearance isn't important (and price is) you might prefer it. -Len Moskowitz Core Sound WWW site: http://www.panix.com/~moskowit [email protected] From [email protected] Wed Aug 20 12:33:48 CDT 1997 Article: 60773 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!vixen.cso.uiuc.edu!howland.erols.net!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] (Jomack) Newsgroups: alt.guitar.amps Subject: Re: 64 DELUXE Foot Switch Help Date: 20 Aug 1997 14:52:49 GMT Lines: 19 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:60773 >I just bought a 64 Blackface Deluxe. It sounds great but there is no >footswitch for the vibrato channel. If I put in an RCA jack and ground it >the vibrato works fine but this doesn't seem practical. Is there a way to >find a switch that works in radio shack or someplace? I'd appreciate any >help. Please copy me via email if you have good advice. [email protected] >>Any Fender dealer can get it for you (Mojo dealers stock 'em too).< >>You'll have to cut off the 1/4" plug and solder in a phono plug. It'll< >>cost around $35.<> >>Alternately, Yamaha dealers have a one button footswitch for around $10.< >>It doesn't look like the Fender but if appearance isn't important (and< >>price is) you might prefer it.<< Or, if you are solderifically challenged like myself, you can buy a adaptor plug 1/4" female to RCA male (Hosa and others), and use ANY 1/4" switch - I use an old Boss FS-2 w/ my Super Reverb - nice long cable and wider spaced buttons- important if you are a bigfoot as I am. Bad Fender Mods From [email protected] Sat Sep 14 10:14:44 CDT 1996 Article: 22710 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntp.primenet.com!newspump.sol.net!news.mindspring.com!usenet From: Bill Hatcher Newsgroups: alt.guitar.amps Subject: Re: Simple Princeton mods? Date: Sat, 14 Sep 1996 11:03:33 +0000 Organization: MindSpring Enterprises Lines: 46 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: user-168-121-165-139.dialup.mindspring.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Server-Date: 14 Sep 1996 10:57:17 GMT X-Mailer: Mozilla 2.02 (Macintosh; U; 68K) Mike Rejsa wrote: > > : Anyone out there have plans for Princeton mods (nothing too complex like > : the Prince of Wails mod or anything)? One day a bolt will come out of the blue and you guys are going to wake up!!! I have! The best mod is NO mod. Between the Champ and the Twin there is a Fender amp that will do what you want without having to jerk out stuff or cram in something else. These things are best left as they are!! Let's all sing!----The Champ amp connected to the Princeton. The Princeton connected to the Delux. The Delux connected to the Tremulux. The Tremolux connected to the Bandmaster. The Bandmaster connected to the Pro Reverb. And on and on. If you want a louder Princeton, the best mod is to buy a Delux. If you want distortion then get a stomp box! If you want a 12" speaker then get a Fender amp that comes with a 12" speaker. If you got something that has already been butchered, then OK, pull out the soldering iron and the chainsaw and have at it. How about some of you guys posting your worst mod of a Fender amp that you have ever seen or done. I will give some I have seen. I have seen several BF Super Reverbs and Twins that have had the head cut out of the cabinet so that the guy who did it would have a separate head. The Super Reverb "head" I saw was connected to a 16 ohm speaker. 2 ohms into 16 ohms!! The guy wondered why it sounded so bad. I gave him $60 for it and told him I could "live" with how bad it sounded! Saw a Brown Tolex Bandmaster Piggy-back amp that someone had taken the amp out of the head, took the back off the speaker cab and cut a slot in the speaker baffle and mounted the amp in there!! Yeah!! More "bullet hole" amps than I care to remember. You know, let's add a master volume to this thing so we need to drill a hole in the O in the word Pro-Reverb. My worst mod that I ever did, before I had my conversion to no- modism, took a Quad Reverb head that someone had already cut out of the cabinet and "sawed off" the normal channel with a hacksaw! Moved the circuit board and tubes and transformers over and put it in a little cabinet with a 12" speaker. I would say it's probably worth about $32 on the open market!! Have to admit that it sounds decent. OK, $42. Come on. Fess' up out there. Reformed, Bill Hatcher PS I bet Tremolux has seen some unbelievable things in his time!! From [email protected] Sat Sep 21 20:09:35 CDT 1996 Article: 23168 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntp.primenet.com!enews.sgi.com!news.sgi.com!news.msfc.nasa.gov!newsfeed.internetmci.com!newsxfer2.itd.umich.edu!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Simple Princeton mods? Date: 21 Sep 1996 18:50:35 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 53 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com >>>PS I bet Tremolux has seen some unbelievable things in his time!! Yes, I have. 1. - Let's start with a brown tolex 2x10 Super where some idiot ripped out the vibrato channel guts and completely rewired it into a fucking high gain Marshall, with a footswitchable relay for switching between the Marshall channel and the still intact normal channel. The amp had a pair of Jensen P10Qs, and they were blown. The owner told me that he's had them reconed several times and they keep blowing so he wanted something that wouldn't blow. I traded him straight across, the pair of blown Qs for Fender blue label ceramics. He was happy. I still have the Qs, but I've had them reconed to stock. 2. - Some other fuckoff cut down a 66 Vibrolux Reverb amp to make a head. The current owner of the resulting "head" has asked me to restore it. I have a repro cabinet on order for him right now. 3. - Lots of BF and SF amps with master volumes installed by drilling a hole in the front panel. Anyone who drills a hole in a Fender's front panel should have a hole drilled in his fucking head with a 1/2 inch bit, right between the eyes. 4. - Someone brought me an old Gretsch amp that some jackoff had tried to re-wire, had gotten half way through, and had then abandoned the project. I had to put it back to stock. Same thing happened with an old Gibson GA-40. 5. - How about a brown tolex Pro where some dipshit hack wired in a reverb section. 6. - Then there's the 65 Super Reverb where someone I know personally (and shall remain nameless, I don't want to be sued) installed HUGE filter caps and the resulting recurring peak charging current was wiping out Mullard 5AR4 rectifier tubes. Causing them to short. After 3 tubes bit the dust, the owner brought it to me to figure out why this was happening. When I installed the correct size filter caps and replaced the rectifier with a new one, the problems have vanished. 7. - Lastly, there was a Narrow Panel Tweed Pro cabinet from 57 or so containing a 53 Pro chassis, with a sign on it saying simply "1957", that was for sale at a show. It had also been re-tweeded and possibly re-grilled. I'm not sure if the speaker was original. Last I heard the dealer wanted $1000 for this frankenstien. I say it's worth $500 tops. These amp butchers, some of them quite famous (you know who I'm talking about), should have their nuts wired to the high voltage supply of a Twin and left to sizzle overnight. Do not support butchers of old Fenders. Leave them the fuck alone. If you want an amp that sounds different from what you have, sell what you have and go buy something with the tone you want. It's simple. Trem. Bandmaster Cathode Bias From [email protected] Sun Jun 16 13:30:01 CDT 1996 Article: 10856 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!uwm.edu!newsfeed.internetmci.com!panix!not-formail From: [email protected] (Mark Garvin) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Cathode Biasing - need a sanity check (please) Date: 16 Jun 1996 05:32:39 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 91 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com Xref: geraldo.cc.utexas.edu rec.audio.tubes:10856 alt.guitar.amps:16964 In <[email protected]> "Mr. Snakey" writes: >I am interested in trying cathode biasing on my AB763 >Bandmaster, and someone on the net was nice enough to >give me a really good explanation of it (thanks, Dave!). >However, I am not an EE, and before I try it, I would like >to lay out the steps as I understand them, and hope that >maybe someone like Mark, Dave, et. al., can take a quick >look for me, and make sure I haven't missed something. I >hate to blow things up 8-/. Awww..you're no fun. >Oh, this BM has been converted to EL34's, using the Fischer >mod from the TAB4. Don't know if that matters. Expect to develop a bit less bias voltage for the EL34's (as compared to 6L6 family), but you can run the current a tad hotter if you wish. >1) Remove ground wire from cathodes (pin 8). >2) Install resistors (10-watt or better) > a) Tie both cathodes together, then run a 500 Ohm resistor > to ground. ----- Supposed to be an OR here, right? ----> b) Run one 1K resistor from each cathode to ground. The separate resistors (b) will require more efficient bypassing, but the single resistor method (a) will be more sensitive to current-hogging if the output tubes are not matched or balanced. >3) Bypass the caps with electolytics (may be optional). Not optional unless you are both running method (a) above, and are definitely staying in class A. >4) Remove bias supply (- voltage) from grids (pin 5). You could stay safe on the first run by converting your bias to go from 0 to say -35 or so (make sure you compute all the resistor wattages in the divider,etc). This will allow you to leave the bias control in the circuit and slowly ramp the 'fixed bias' voltage to 0, monitoring the voltage at the cathode resistor as you do this. This is just a precaution to make sure you don't toast tubes if something is not wired correctly. >-->Here I get fuzzy<-- >??? 5) Hook bias supply to cathodes (doesn't seem right...) Nope...the current pulled thru the output tubes develops a voltage across the cathode resistor. The output tubes' grids are at 0 volts, but the cathode now goes positive. The bias voltage is actually the voltage from the control grid (signal grid) to the cathode, so it will still 'look' like a negative value. Follow? In other words, the cathode will still be more positive than the grid. >I'd appreciate any clarification. Posting is fine; If you >can e-mail, too, that would be smashing, since my feed runs >about 3 days behind 8-[. Posted and emailed, but please direct replies to the news group. >Oh, and if I forgot something _please_ let me know >8-0. Well, if you use the single resistor method, then you will know how much current BOTH output tubes are drawing, but you won't know if they are balanced. So you might consider putting 1 ohm resistors between the cathodes and the BFR (big resistor). You'll be able to tell individual tube current by monitoring the voltage across each 1-ohm resistor. Also, make *sure* you get the bypass cap polarity straight. And use very good quality bypass caps. If they short out, they will effectively remove the bias voltage, which will red-plate your tubes in a hurry. MGarvin PS: Be careful and have fun. From [email protected] Mon Jun 17 00:46:21 CDT 1996 Article: 10882 of rec.audio.tubes Newsgroups: rec.audio.tubes,alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!world1.bawave.com!news2.cais.net!news.cais.net!vanbc!nntp.portal.ca!news.bc.net!arclight.uoregon.edu!netnews.worldnet.att.net!cbgw2.att.com!oucsboss!cigna From: [email protected] (Dave Cigna) Subject: Re: Cathode Biasing - need a sanity check (please) X-Nntp-Posting-Host: helios.phy.ohiou.edu Message-ID: Sender: [email protected] X-Nntp-Posting-Date: Sun Jun 16 10:07:01 1996 Organization: Ohio University Physics and Astronomy References: <[email protected]> Date: Sun, 16 Jun 1996 14:07:02 GMT Lines: 67 Xref: geraldo.cc.utexas.edu rec.audio.tubes:10882 alt.guitar.amps:17011 In Mr. Snakey wrote: >I am interested in trying cathode biasing on my AB763 >Bandmaster, and someone on the net was nice enough to >give me a really good explanation of it (thanks, Dave!). > >However, I am not an EE, and before I try it, I would like >to lay out the steps as I understand them, and hope that >maybe someone like Mark, Dave, et. al., can take a quick >look for me, and make sure I haven't missed something. I >hate to blow things up 8-/. >Oh, this BM has been converted to EL34's, using the Fischer >mod from the TAB4. Don't know if that matters. > >1) Remove ground wire from cathodes (pin 8). >2) Install resistors (10-watt or better) > a) Tie both cathodes together, then run a 500 Ohm resistor > to ground. > b) Run one 1K resistor from each cathode to ground. This should be (a) OR (b). You should probably choose (a) in your case. Some amps that are running class A, or close to it, sound good with separate cathode resistors. >3) Bypass the caps with electolytics (may be optional). Lately, I've come to the conclusion that bypass caps are never optional in power amps. Preamp tubes are a different situation. You want the cap to be big enough to work at low frequencies. There is no hard and fast rule, but if you choose one that is 30000/R (uF) or bigger, then that should be big enough. >4) Remove bias supply (- voltage) from grids (pin 5). > >-->Here I get fuzzy<-> >5) Turn on the power, and enjoy cathode biasing > >-or> >5) Hook bias supply to cathodes (doesn't seem right...) >6) Turn on the power and ... as above. Hmm... It's important that the grids are referenced to some steady voltage through 'grid load' resistors. In a stock Bandmaster each grid is connected to about -50 volts (bias supply) through a 220k resistor (silverface amps may vary.) With cathode biasing, you want to connect each grid to 0 volts (ground) through a 220k resistor. Fortunately, this is very easy to do on many Fender amps. Near the end of the eyelet board, by the tremelo controls you'll find a pair of 220k resistors that form a "V" shape (silverface amps might be different.) Don't confuse these with the phase inverter plate resistor that also form a "V" (probably 100k/82k.) One end of each resistor is connected to a cap and also to the grid of one power tube via a wire under the eyelet board. The other ends of the resistors are joined together and connected to the bias supply via a wire that might start under the eyelet board. What you need to do is disconnect this wire *from the bias supply* and reconnect to ground. Make sure that the ground connection is good and reliable. A flaky connection here could spell disaster for your power tubes. -- Dave Cigna Bassman 10 info From [email protected] Sun Jan 7 09:37:55 CST 1996 Article: 7588 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uunet!in2.uu.net!prodigy.com!usenet From: [email protected] (Jack Price) Newsgroups: alt.guitar.amps Subject: Re: Q: SS rectifier on '65 Super? Date: 7 Jan 1996 07:40:05 GMT Organization: Prodigy Services Company 1-800-PRODIGY Lines: 28 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: inugap1.news.prodigy.com X-Newsreader: Version 1.2 [email protected] (Nathan Stewart) wrote: >What are the speakers in the Bassman Ten - I don't really care for the amp, >but my homebuilt 15 watter absolutely screams through my roomate's BT. The Bassman 10 came with really cheezy Utah 32ohm 10"ers wired in parallel. Yes I said 32ohm. I was surprised too. Had one in the shop awhile back with 3 speakers out of four blown, froze actually. The fourth ohmed out at the equivalent of 32 ohms. I replaced the speaker with MojoTone MP10RD's wired in series-parallel for a total load of 8ohms. Amp was totally killer. These amps are ideal canidates for a reverb add on. There's plenty of room on the fiber board for components and room on the chassis for two extra tubes. Reverb tank can fit inside the cabinet which is only accessable by removing at least one of the speakers. These amps have gotten a bad rep through the years and thus can be picked up cheap. BUT...they can be converted to sound pretty similar to a Super Reverb for another ~ $150. PriceLess Vintage Tube Amp Restorations (503) 641-7146 JACK PRICE [email protected] Bassman Head Running 2ohms From [email protected] Thu Aug 5 19:13:47 CDT 1999 Article: 194178 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.nyu.edu!novia!sequencer.newscene.com!notfor-mail From: Ned Carlson Newsgroups: alt.guitar.amps Subject: Re: Can Bassman Run 2 Ohms? Date: 5 Aug 1999 00:53:21 -0500 Organization: Triode Electronics Lines: 34 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] X-Mailer: Mozilla 4.5 [en] (X11; I; Linux 2.0.36 i586) X-Accept-Language: en MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Xref: geraldo.cc.utexas.edu alt.guitar.amps:194178 Thorny wrote: > You could rewire a concert cabinet in a series/parallel combination to > give it 8 ohms resistance from what I have read, but if the concert > amp is functional, you may not want to do this. Also, it is not a > match, but it is safer than using 2 ohms (as I understand it from > listening to the guys that know what they are talking about on this > group). Man, I think it's about time for the Big Giant Heads to get together and write an FAQ for this newsgroup so these questions get straightened out ahead of time. This must be the 340th time this question has come up. If you've *got* to run a mismatch on a tube amp, especially on an amp which one can pretty much count on being overdriven, *lower* is better than higher. The BF Bassman heads actually had a main and extension speaker jacks, on which the ext speaker DOES NOT WORK unless you've got the main speaker *plugged in*. This means Fender themselves believed that running into a lower impedance was OK. Running into a higher impedance, especially if one wants distortion, is NOT a good idea, as one takes the chance of encountering the dreaded flyback effect (the higher the wattage of the amp, the bigger the dread). DFE can blow hell out of transformers, sockets & tubes. -Ned Carlson Triode Electronics "where da tubes are!" 2225 W Roscoe Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun http://www.triodeel.com Beef Up Tweed Champ From [email protected] Wed Nov 19 22:41:41 CST 1997 Article: 72442 of alt.guitar.amps From: [email protected] Subject: Beefing up a Tweed Champ or Princeton Date: Wed, 19 Nov 1997 16:12:41 -0600 Message-ID: <[email protected]> Newsgroups: alt.guitar.amps Organization: Deja News Posting Service Path: geraldo.cc.utexas.edu!cs.utexas.edu!www.nntp.primenet.com!globalcenter1!news.primenet.com!nntp.primenet.com!cpknewshub1.bbnplanet.com!news.bbnplanet.com!newsfeed.internetmci.com!204.238.120.130!jump.net!grunt.dejanews.com!notfor-mail X-Article-Creation-Date: Wed Nov 19 18:19:29 1997 GMT X-Authenticated-Sender: [email protected] X-Http-User-Agent: Mozilla/2.0 (compatible; MSIE 3.01; Windows NT) X-Originating-IP-Addr: 199.173.224.2 (s3abab9.ssa.gov) Lines: 29 Xref: geraldo.cc.utexas.edu alt.guitar.amps:72442 Hey Everybody, I just finished building a homebrewed Tweed 5F2A Princeton style amp, and would like to share a little insight on to how add some beef to any Tweed Champ/Princeton circuit that uses 12AX7 preamp tubes. First, and foremost, add a 22uf/50 cathode bypass cap to the second preamp stage. This cap will increase gain by 3db on frequencies above 4.8hz. This mod will push you into the cranked plexi level of gain on volume settings above 6 (i.e., the amp will sustain and feedback). Additionally, some of the Tweed circuits (5F1 Champ and 5F2 Princeton come to mind) have no cathode bypass cap on the first gain stage. Bypassing the 1.5K cathode resistor with a 22uf/50v will also have the effect of increasing gain, on this stage, by 3db on frequencies above 4.8hz. If you want that hard-edged bright Marshall tone, replace the 1.5K cathode resistor, on the first gain stage, with a 2.7K resistor, and use a .68uf plastic cap as the bypass cap. This mod will give you a gain and increase of 3db on frequencies above 86.7hz. The resulting sound will be much brighter and tighter with a harder-edged crunch. Mark -------------------==== Posted via Deja News ====----------------------http://www.dejanews.com/ Search, Read, Post to Usenet Birth of Fender Reverb From [email protected] Wed Jul 3 11:08:09 CDT 1996 Article: 18069 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!howland.reston.ans.net!newsfeed.internetmci.com!news.connectnet.com!max-lj-n250.connectnet.com!user From: [email protected] (Rory Wicks) Newsgroups: alt.guitar.amps Subject: The Birth of Reverb Date: 3 Jul 1996 01:52:18 GMT Organization: CONNECTnet Internet Network Services (service provider) Lines: 34 Message-ID: NNTP-Posting-Host: max-lj-n-250.connectnet.com Rhino Record¹s surf music compilation ³Cowabunga² discloses the birth of reverb. Dick Dale states that his first album ³Surfers¹ Choice² (Deltone Records 11/62) had no reverb: ³ . . . But if you listen to that album closely, you won¹t hear one decibel of a sound resembling a Fender reverb, because it had not yet been invented! The reverb came about after I explained to Leo Fender and Freddy T., his number one man, that I didn¹t have a natural vibrato in my voice, and that my live show was 95 percent singing and that my guitar played the leads while I sang. I wanted to sustain my voice like you can a piano note by pushing down on the sustain pedal. The note just hangs there. I told Leo that I had a Hammond organ at home, and it had a button that gave you a reverb sound that was closer to what I wanted for my voice. Leo built a device that had a Hammond Organ Company spring tank mounted inside, and when I plugged a Shure Dynamic birdcage microphone into it, I was able to sing and sound like Elvis. That was the birth of the Fender reverb. Later, when I plugged my Stratocaster into the reverb and played some of my instrumentals, it was the icing on the cake. Only then did my Fender reverb sound become associated with surf music.² Mr. Dale is indeed correct. Fender licensed the design of the reverb system from the Hammond Organ Company, put the system in a small box with electronic circuitry, and gave Dale the prototype in 1961. One year later, in 1962, Fender began selling the reverb for $129. Rory Wicks [email protected] Blackface Cabinet Dates From [email protected] Mon Feb 26 14:02:33 CST 1996 Article: 10466 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!news.texas.net!news1.best.com!news.exodus.net!imci4!newsfeed.internetmci.com!swrinde!tank.news.pipex.net!pipex!news.uoregon.edu!news.mind.net!news.onramp.net!usenet From: Nick Schepis Newsgroups: alt.guitar.amps Subject: Re: Yard Sale Fender Super Reverb Date: 25 Feb 1996 15:58:07 GMT Organization: On-Ramp; Individual Internet Connections; Dallas/Ft Worth/Houston, TX USA Lines: 19 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: stockyard49.onramp.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 1.22 (Windows; U; 16bit) craig_o'[email protected] (craig o'donnell) wrote: >Silver faced Supers need some small modifications to sound as good as the >black units. If silver it could be anywhere from, 1969 on. Some people >can date these amps more precisely, I can't. Silver started in 1968. While on the subject, Mr. Van Zandt (the pickup guy, sorry, can't remember his first name) was looking at a 1966 Super Reverb of mine and showed me a little trick I hadn't seen before. He asked me how I dated the amp, I told him by the speakers. He told me to lift of the reverb tank and look at the botom of the cab for a number faintly stamped in black ink. He asked me what the last two numbers were and right there it was '66'. I checked all my blackfaces and there it was, however faintly. Good way to see if the cabinet matches the speakers, chassis, etc... NS Blackface Pro From [email protected] Fri Jun 16 13:52:50 CDT 1995 Article: 54702 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: rec.music.makers.guitar Subject: Re: Q: Fender Pro or Pro Reverb Date: 16 Jun 1995 02:28:44 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 10 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com A buddy of mine picked-up a BF Pro Amp at a show for $350. It was good cosmetically, but the C15N needed a recone job. Also there were some minor circuit mods that I took out for him, and put it back to stock. That amp sounds great and is LOUD. All you need is an external reverb. Since it uses the same output transformer as the Vibroverb, and the plate voltages are CLOSE, power is nearly as high. The most massively FAT tone comes from a real BF Vibroverb with the JBL. Regards. Blame UL From [email protected] Mon Jan 13 22:02:35 CST 1997 Article: 34284 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!ennfs.eas.asu.edu!nntp.dist.maricopa.edu!usenet From: Dale VanZile Newsgroups: alt.guitar.amps Subject: SF Fender wiring changes--blame UL, not Fender Date: Mon, 13 Jan 1997 16:33:28 -0700 Organization: Maricopa Community Colleges Lines: 28 Message-ID: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: mac43.stu-serv-2.sc.maricopa.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Macintosh; I; PPC) I've been watching this newsgroup via Harmony-Central's archive page, but now I've finally gotten my news server to let me in. Anyway, the topic of SF-BF conversion has led to a comment by <> to the effect that Fender got lazy and failed to follow their earlier wiring routing layouts, and that that's the reason for the parasitic osc. caps being added to the circuits. I believe that the true reason they moved that wiring was due to UL's pressure to move away from the cloth-covered wire and to a flame-resistant plastic insulation. This plastic-covered wire sadly does not hold up well when routed under the circuit board the way Fender ran the cloth-covered wire. The wire's insulation melts /very/ easily when soldering the wire to an eyelet or pot lug, and wires run under the board tend to short out all over when this happens. A friend of mine tried running the plastic-insulated wire under the board on a SF once, and ended up having to rewire the thing all over again........ So, since they couldn't use their old wiring scheme, they changed it, and found that the amps then frequently had problems with parasitic oscillations. Progress. Yay. ;) It just happens that the switch to SF happened at about the same time as the switch in circuitry ("to get rid of all that nasty distortion") and the UL pressure. I've seen some early SF amps with the original BF circuitry and cloth wire. They sound just like the BF units, and can usually be had a lot cheaper than a similar BF unit. Dutch [email protected] From [email protected] Tue Jan 14 10:43:34 CST 1997 Article: 34368 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newspump.sol.net!ddsw1!news.mcs.net!notfor-mail From: "Teleologist" Newsgroups: alt.guitar.amps Subject: Re: SF Fender wiring changes--blame UL, not Fender Date: 14 Jan 1997 13:06:12 GMT Organization: CT&T Lines: 17 Message-ID: <01bc021c$2bcfcdb0$610258aa@alsnt> References: <[email protected]> NNTP-Posting-Host: ctt-ext.ctt.com X-Newsreader: Microsoft Internet News 4.70.1155 Dale VanZile wrote in article <[email protected]>... > I've been watching this newsgroup via Harmony-Central's archive > page, but now I've finally gotten my news server to let me > in. Anyway, the topic of SF-BF conversion has led to a comment > by <> to the effect that Fender got lazy and > failed to follow their earlier wiring routing layouts, and > that that's the reason for the parasitic osc. caps being > added to the circuits. I believe that the true reason they > moved that wiring was due to UL's pressure to move away from > the cloth-covered wire and to a flame-resistant plastic > insulation. > Interesting post, however CBS/Fender's 'cost-saving' measures are well documented - they could have used a higher quality plastic wire to avoid melting problems. :) Blues Deluxe review From [email protected] Tue Aug 22 09:24:54 CDT 1995 Article: 3032 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!swrinde!news.uh.edu!uuneo.neosoft.com!usenet From: [email protected] (Dr. Nuketopia) Newsgroups: alt.guitar.amps,alt.guitar,rec.music.makers.guitar Subject: Blues Deluxe review (update on Holy Grail) Date: 21 Aug 1995 19:40:21 GMT Organization: Merak Projects, Inc. (USA) Lines: 124 Message-ID: <[email protected]> NNTP-Posting-Host: nixon.merakusa.com Mime-Version: 1.0 X-Newsreader: WinVN 0.99.3 Xref: geraldo.cc.utexas.edu alt.guitar.amps:3032 alt.guitar:56808 rec.music.makers.guitar:61845 Thanks for all the comments about my search for the Holy Grail sound. Weighing all factors, I bought a Blues Deluxe on Friday. Traded my Performer 650 in and walked out with a new-in-the-box Blues Deluxe for under $300, tax included. I have to say this is pretty darn nice sounding amp. It's not the Holy Grail, but its a good deal for a small price. At least it has the right kind of tone. It does get a very legitimate classic tube tone. This amp is also quite loud, and works very well at high volume levels. It has the classic Fender tone, with a few modern updates to lower cost and provide 1995 features. Noise levels, both hiss and hum were acceptabley low. This amp sounds ok at low levels but gets really sweet when cranked. Though it is built well enough for gigging and such, it lacks some features for hard-core road warriors. One is the tubes are not held in by spring retainers or sheilds. The outputs have base clips, while preamp tubes are partially recessed for sheilding. It's certainly tough enough for jamming, and around-the-town gigs. Here's the tech review: 3 - 12AX7 Sovtek 2 - 5881 Sovtek Signal path is all tube, though Reverb is driven by TL072 Audio chip. The reverb pan is the long spring type. The effects loop is bufferd by TL072's. Not using the effects loop bypasses the TL072 buffers, so the signal path is tube-to-tube. One button footswitch control to switch between drive and normal channel. Has 2 inputs, #1 is high-impedance, #2 is low-impedance, 1+2 together is high impedance for both. Chassis construction is a good quality fiberglass PC board, with tube sockets soldered on a sub PC board. Component side of chassis is exposed when the tube guard is removed. Single-sided PC board is well layed out, road-mapped on top, solder masked on bottom. Board removal is about 5 screws, plus all the nuts from the top panel jacks and controls. Chassis has *plenty* of room for mods. Transformers etc, attached by plugs to PC board, should make servicing easier. Cabinetry is particle wood, with a multi-core pine plywood speaker baffle (either a 1/2 or 5/8 thickness just looking at it.) Baffle is attched by 6 nuts and screws to the cabinet. Circuit features: Power: AC supply has an NTC thermistor in line to limit inrush current on turn on. Silicon diode full-wave bridge develops primary plate voltage of 427v, loaded into to 100uf @350v caps (series for 50uf), then a choke, feeding 2 more 100uf caps which feeds the screen supply, then a resistor divider network for the pream stages. Filament and pilot are derived from a 6.7vac winding, ground balanced by 2-47ohm resistors. A 50 volt winding supplies zener regulated power to the TL072 chips and channel switching chips, along with the negative bias voltage for the output grids. The negative bias is non-adjustable, taken between a 3k and 27k resistor divider. (this needs a tweek) Bias is fixed at about -46 volts. Signal: The amp offers 2 channels, with footswitch operation. The normal channel is simple volume, tones, reverb. The drive channel includes a drive and master volume as well. The preamp employs 3 gain stages, leaving one section of 12AX7 unused. The amp does not implement discrete channels for drive and normal, but employs 2 small relays to switch the master volume and drive or the normal volume controls. Switching also effects the gain parameters of the pre-amp stage, adding a bit of boost in drive (though not too much). The reverb is driven by TLO72 opamps, configured in a send/receive pair. Reverb is after volume and tone, and mixes in at the phase inverter. The amp has fixed level effects loop, with a non interrupting pre-amp out and a interrupting amp in jack. The loop is buffered by a pair of TL072 op amps. However, if the amp-in jack is not used, the signal bypasses the loop buffers for a tube-only signal path. (nice touch) Phase inverter uses two sections of a 12AX7, configured in a differential pair, rather than the more common single section voltage divider inverter. Output is provided by 2 Sovtek 5881/6L6 wired in a conventional push-pull pair. No provision is made for measuring idle current or adjusting the grid bias. Screens are powered through resistors to the choke side of the power supply. The transformer has 4 and 8 ohm taps, though only 1 speaker jack is provided, using the 8 ohm tap. The 4 and 8 ohm transformer taps are easily swapped however, so changing speakers should not be too much trouble. The output transformer is kind of smallish, but looks to be more than adequate for the job. Power is rated at 38 watts RMS @1khz with no more than 5% THD. Output stage negative feedback is coupled through the presence control, which alters the frequency curve of the feedback signal. Feedback is applied at the input of the phase inverter. Speaker is one Gold Label Fender by Eminence "vintage re-issue" (tweek candidate). Overall quality of components and workmanship is pretty good. I'd have to say this amp represents an excellent value. List price is around $650, though street price is around $420. It's also covered by a 3 year warranty. -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy Opinions strictly reflect the party line From [email protected] Thu Aug 24 15:03:14 CDT 1995 Article: 3099 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!news.uh.edu!uuneo.neosoft.com!usenet From: [email protected] (Dr. Nuketopia) Newsgroups: alt.guitar.amps,alt.guitar,rec.music.makers.guitar Subject: Re: Blues Deluxe review (update on Holy Grail) Date: 24 Aug 1995 16:55:41 GMT Organization: Merak Projects, Inc. (USA) Lines: 70 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: nixon.merakusa.com Mime-Version: 1.0 X-Newsreader: WinVN 0.99.3 Xref: geraldo.cc.utexas.edu alt.guitar.amps:3099 alt.guitar:57202 rec.music.makers.guitar:62142 In article <[email protected]>, [email protected] says... > >Solid state reverb in a Blues Deluxe? Wanna bet? I just checked my Blues >DeVille (same setup as a Blues DeLuxe) and there a very nice Accutronics >reverb pan in the bottom of the cab. Now, the reverb drivers and >recovery in both of these are op-amps, instead of tubes, but this would >not give the same sound as a solid-state reverb (I gots one of those, >too, so I know the difference.) A tube send and recovery would be nice, >but then the amp would probably sell for $75.00-$100.00 more with the >tubes, and Fender's price point would be missed by quite a large margin. > Yup. Adding a full tube reverb would easily add $100 to the price, maybe more. A good audio IC can do a very competent job with reverb. Maybe I wasn't clear enough in the review. TL072's are high-quality, FET input, low-noise, high slew rate, small signal audio op-amp chips made by Texas Instruments. As op-amps go, they are pretty darn good, suitable for hi-fi and other demanding audio usage. These chips are most definitely anolog IC's. They perform the same function as a tube section and a bunch of resisistors and caps and such. Since they cost about a buck and do a pretty good job, I'd have to say Fender was pretty smart to use them in this manner to save money. The reverb pan in the Deluxe is the same one used in Fender's better amps. It's the long Accutronics, not the skimpy little short one used in the cheaper amps. The reverb system is totally analog. It uses solid state IC's to drive and recover the reverb signal from the pan. NO delay chips are used, analog or digital. The TL072's are used to bufer the effects loop jacks too. This too is a smart idea, it cuts cost, and IC's are better able to deal with the widely varying impedances and loads external devices are likely to present. The power amp-in jack is wired in such a way that if you don't plug in anything, the op-amps are bypassed, sending the signal from the preamp tube stage on to the phase inverter tube. That's a pretty nice touch by the engineer. The Fender of the past would have just cheesed the signal all the way through the IC's. Now, if you are a purist, the Blues Deluxe (and DeVille since they share the same PCB and design) will pass the signal entirely through tubes if you: A: Do not use the effects loop. B: Turn reverb control all the way down (or off) Use it like this, and the circuit is very similiar to the early tweed Bassman amps. Eerily similar actually. Though I apreciate the sound of tubes, there are cases where IC's make sense. I think the Blues Deluxe design makes wise use of 1995 technology, while still retaining a very legitimate tube design and sound. Cheers, y'all -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy Opinions strictly reflect the party line -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy Opinions strictly reflect the party line Brown Bassman Transformers From [email protected] Wed Oct 16 23:01:05 CDT 1996 Article: 24910 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!feed1.news.erols.com!super.zippo.com!zdc!zippo!news From: [email protected] (Timothy J. Richter) Newsgroups: alt.guitar.amps Subject: Re: Fender Bassman Heads Date: Wed, 16 Oct 1996 05:38:51 GMT Organization: Zippo Lines: 60 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: du-14.alonline.com X-Newsreader: Forte Free Agent 1.0.82 >On the subject of speakers: Prior to sometime in '62, the cabinet used a >single speaker mounted on a "tone ring", an interesting way of porting the >speaker. After '62, Fender went to a 2-speaker configuration. It's very >important to make sure the head matches the cabinet, since >the heads >designed for the single speaker have an 8-ohm output transformer and the >heads designed for the two-speaker configuration have a 4-ohm output >transformer. There is an EASY way to tell which head you have: If it has a >tube rectifier, it's an early 8-ohm, single-speaker head; If the amp uses a >solid state rectifier circuit (no tube rectifier, but a round plug where the >tube would go), it was designed to go with a 4-ohm, 2-speaker output. This >is, of course assuming that someone hasn't replaced the output transformers. While this is right in 90% of the cases, it is not always the case that a Bassman with a tube rectifier has an 8 ohm output transformer. I have a 100% stock Blonde tolex Bassman. The date code is "LA" (Jan. 1962), and I have a silicon diode (SS) rectifier. BUT, my amp has an 8 ohm transformer. Here is a 100% test that cannot fail. (I think) Each output transformer (if original) has a part number stamped (or sometimes inked) onto the metal end bell encasing the wiring. It will have 6 digits and begin with 125... If it is a 125A5A it is definitely an 8 ohm tranny. If the number is 125A13A it is a 4 ohm tranny. Also, I would disagree that it is "very important" to make sure that the cabinet matches the speakers. In 90% of the cases, you will have a non 1961 Bassman and it wants to see a 4 ohm load. Most common are 8 ohm 12"s. (fender rarely used 16 or 4 ohm speakers), so it is likely that a 2x12" box will match with 90% of Bassman heads. BUT...Wait!! an 8 ohm load will not be optimal for a later Bassman, but it will not be disasterous. Fender amps are tolerant (moreso than Marshalls) and many times throughout Fender History a speaker load mismatched the amp. (Think of the EXT SPKR jack--c'mon, did anyone realty change out their Deluxe Reverb 8 ohm speaker to a 16 ohm and use a 16 ohm ext cab??!!)... Anyway. I too have a 1962 Bassman (2 in fact, one with the 8 ohm OT and one with the four). Just tonight I used the 4 ohm 62 Bassman with a Marshall 8 ohm 4x10" and got the most KILLER tone I have gotten from that amp. Anyway, many will tell you that mismatching ohms will kill a tube amp, but in my experience, a 100% mismatch is OK (8 ohm load on a 4 ohm OT, or a 16 ohm load on a 8 ohm OT, or even a 4 ohm load on a 8 ohm tranny) >Personally, I have a '62, double-speaker, blond bassman rig that sounds >great with a guitar. It has that one sound, but it's a nice one. I'll agree. A limited amp, but what a sound it makes!!! Also, if you doen't mind modding an amp (gosh!! eeek!) If you like the NORMAL channel and want to rewire the BASS channel, you've got three knobs and 2 tubes (4 gain stages) to work with. (I built a Marshall pre-amp into the BASS side of a BF Bassman --now it's a versitile amp!) Just my 0.02 Tim Brownface Trem Pulse From [email protected] Sat Aug 22 00:59:57 CDT 1998 Article: 122708 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!portc02.blue.aol.com!audrey03.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Brown Fenders Lines: 18 Message-ID: <[email protected]> NNTP-Posting-Host: ladder03.news.aol.com X-Admin: [email protected] Date: 20 Aug 1998 22:34:19 GMT Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:122708 >>Anybody spend much time with the brown pitch-vibrato amps? >I've found I can't increase the value of the p/i input cap (.001) without >getting the awful "beating" when the vibrato is in use. >I'd like to thicken up the tone a bit. Already subbed .022 tone caps and >biased >my NOS 6L6's to 35mA per tube. >Any suggestions? > >Matt D > I've spent some time with those circuits. the small cap at the PI input is used to kill the subsonic artifact signal coming from the 12AX7 that does the actual modulation in the circuit. It functions as a single pole high-pass filter in conjunction with the PI's input impedance. There's nothing you can do to eliminate it entirely. You can minimize it by hand selecting the 12AX7. Just try different ones, and one will have less of the beating than the others. Brownface Tremolux Cabinets From [email protected] Wed May 21 20:44:39 CDT 1997 Article: 50484 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!howland.erols.net!feeder.chicago.cic.net!ddsw1!news.mcs.net!notfor-mail From: "Teleologist" Newsgroups: alt.guitar.amps Subject: Re: 5881s in a Twin? Date: 22 May 1997 01:19:50 GMT Organization: MCSNet Services Lines: 22 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> <01bc65dd$5883c620$610258aa@alsnt> NNTP-Posting-Host: ctt-fw.ctt.com X-Newsreader: Microsoft Internet News 4.70.1155 Xref: geraldo.cc.utexas.edu alt.guitar.amps:50484 Teleologist wrote in article <01bc65dd$5883c620$610258aa@alsnt>... > Thomas C. Clancy wrote in article > <[email protected]>... > > Well, I wonder what it is then?: rough white tolex, oxblood. >> > > 17.5 x 27.5. The distance between the centers of each mounting > > screw hole is exactly 24". >> > The dimensions match those of a Tremolux cab. The very early piggyback > Tremolux cab came with a single 10" speaker. I'm not sure if it had the > Tone-Ring. > Sorry, I missed your 1st post about how many speakers it had. The second version Tremolux cab had the 2x10 configuration with the same dimensions. According to "Fender Amps" the change to 2x10s occured in early 62 with rough white/oxblood for a short time and then changed to wheat late in 62, smooth white/gold sparkle in late 63, and BF in 64. As you've already figured out, 12's will fit in there just fine! BTW the earlier 1x10 did have the tone ring and a Tremolux head is 23" wide. CBS Deluxe Reverb Changes From [email protected] Sun Jan 4 00:42:23 CST 1998 Article: 78476 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer.sprintlink.net!news-peerwest.sprintlink.net!news.sprintlink.net!Sprint!newsfeed.wli.net!feed.nntp.acc.ca!204.92.54.104.MISMATCH!news.ican.net!notfor-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: When did Fender change the Deluxe Reverb (not other amps)? Date: Sat, 03 Jan 1998 02:08:14 -0500 Organization: ACC TelEnterprises Ltd. Lines: 39 Message-ID: <[email protected]> References: Reply-To: [email protected] NNTP-Posting-Host: ppp-220.m2-14.tor.ican.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.ican.net 883808416 3182 (None) 142.154.22.220 X-Complaints-To: [email protected] X-Mailer: Mozilla 2.02 (OS/2; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:78476 Jim Kroger wrote: > > I know the internals of other silverface amps began to change as early as > 1968 (Twin, Super...) and others remained untouched for years (Champ, Princeton > Reverb), but I have heard conflicting reports about the fate of the Deluxe > Reverb. I'm about to check out an early silverface, is there any chance it > is like a blackface DR inside? > > Also, when they started changing things, didn't they change the > transformers, such that you can not completely revert the amp back to > blackface specs? When did that happen? 68 or 69 i used to know .. fender did very little to the deluxe reverb to mess it up ... snubber caps on the outputs and reverb appeared as soon as cloth wire was dropped in favor of plastic wire I had a 69 that was cloth wired and had very few changes .. however it did have the slightly taller power transformer spec ed for the 5u4 rectifier ... most of these 5u4 amps require some caution when converting back to gz34 rectifier as some extra voltage was added to the power transformer to compensate for the 5u4 rect.. as a result a gz34 in one of these deluxes could exceed the output tubes voltage limits... as with any cbs era amp fender was constantly switching vendors to try and keep parts prices low as a result the cds amps are not as consistent as the blackface era even if the amp is not "altered" for my .02 worth of opinion the silver deluxes are my favorite cbs era amp as most of them sounded good for the record i have one silver face amp left .. it is a deluxe reverb.. pat Champ 8ohms From [email protected] Thu Aug 31 22:05:16 CDT 1995 Article: 691 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!natinst.com!news.dell.com!swrinde!howland.reston.ans.net!news.sprintlink.net!news.interport.net!blackie.port.net!blackie From: [email protected] (Blackie Pagano) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Running Champ with 8 ohms instead of 4 ohms Date: Thu, 31 Aug 1995 09:03:12 UNDEFINED Organization: Interport Communications Corp. Lines: 13 Message-ID: References: <[email protected]> NNTP-Posting-Host: blackie.port.net X-Newsreader: Trumpet for Windows [Version 1.0 Rev B final beta #1] Xref: geraldo.cc.utexas.edu rec.audio.tubes:691 alt.guitar.amps:3263 In article <[email protected]> [email protected] (Mark Garvin) writes: >I realize that there were quite a few different transformers >used in Champ tube amps (the single 6v6 version). But has >anyone here had trouble running an 8 ohm speaker instead of >the 4 ohm standard? >Any experience or theories welcome. People do it sometimes, out of ignorance or just plain unavailability of a 4 ohm speaker. At best, you merely lose some of that raging 3-6 watt Champ output. At worst, the transformer will arc from being run out of spec. I've seen both scenarios. At this point, the only champ speaker that is tough to get is the 4 ohm 6" in early circuits. From [email protected] Thu Aug 31 22:06:01 CDT 1995 Article: 722 of rec.audio.tubes Newsgroups: rec.audio.tubes,alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newsfeed.internetmci.com!newshost!news From: [email protected] (Mark Amundson) Subject: Re: Running Champ with 8 ohms instead of 4 ohms X-Nntp-Posting-Host: 138.64.19.128 Message-ID: Sender: [email protected] Organization: Alliant Techsystems X-Newsreader: WinVN 0.93.14 References: <[email protected]> <[email protected]> Mime-Version: 1.0 Date: Thu, 31 Aug 1995 18:53:23 GMT Lines: 65 Xref: geraldo.cc.utexas.edu rec.audio.tubes:722 alt.guitar.amps:3271 In article <[email protected]>, [email protected] says... > >>In article <[email protected]> [email protected] (Mark Garv >in) writes: >>>I realize that there were quite a few different transformers >>>used in Champ tube amps (the single 6v6 version). But has >>>anyone here had trouble running an 8 ohm speaker instead of >>>the 4 ohm standard? >>>Any experience or theories welcome. > >In [email protected] (Blackie >Pagano) writes: >>People do it sometimes, out of ignorance or just plain unavailability > of a 4 >>ohm speaker. At best, you merely lose some of that raging 3-6 watt Ch >amp >>output. At worst, the transformer will arc from being run out of spec >. I've >>seen both scenarios. At this point, the only champ speaker that is to >ugh to >>get is the 4 ohm 6" in early circuits. > >Transformer arc is exactly what I'm concerned about. It seems that Fe >nder >used normally-closed speaker jacks to avoid transformer arcing, since >I can imagine no other reason to do that. And since I don't have spec >s >on Fender transformers, I assumed that this may be an indication they >are >prone to arcing. > >The lack of selectable speaker impedance, and the presence of external >speaker jacks on most Fender amps also leads me to believe that maybe >their primaries are spec'd a bit high to begin with (to allow reduced >speaker impedance without maxing out power tube dissipation). > >Does anyone have data on Fender (or other guitar amp) transformer >primary impedances? > >Regards, >Mark G. The primary impedance is nominally 5000 ohms. These transformers are pretty universal here. I have 1959 National student amp with the exact 12AX7/6V6GT/5Y3GT circuit has the same vintage Fender Champ. My National drives a 3.2 ohm 8 inch Jensen Special Design speaker and the output transformer has a 3.2 ohm secondary to match (completely stock). Thordarson makes 4 single plate to voice coil transformers with primary impedances of 2000, 4000-5000, 5000, and 7000-10,000 ohms. Each is rated at 5 watts into 3.5 ohm voice coil secondaries. Stancor also offers a 10,000 ohm center tapped at 10 watts with 6-8/3.2-4 ohm secondaries. It is made for push-pull 6V6's but will work for champs. Hammond also offers 3, 5, 8, and 10 watt universal single plate to voice coil transformers. Primaries are center tapped and the secondaries have four taps for a 1200 to 25,000 ohm primary to a 1.5 to 15 ohm secondary. The reason for shorting secondaries in tube outputs is to present only a high impedance inductive load if the speakers are present. The output tube sees only a small inductor here. If the secondary is opened, it acts like a flyback circuit and may induce arcing. From [email protected] Thu Aug 31 22:06:50 CDT 1995 Article: 686 of rec.audio.tubes Newsgroups: rec.audio.tubes,alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!natinst.com!news.dell.com!swrinde!gatech!newsfeed.internetmci.com!newshost!news From: [email protected] (Mark Amundson) Subject: Re: Running Champ with 8 ohms instead of 4 ohms X-Nntp-Posting-Host: 138.64.19.128 Message-ID: Sender: [email protected] Organization: Alliant Techsystems X-Newsreader: WinVN 0.93.14 References: <[email protected]> Mime-Version: 1.0 Date: Thu, 31 Aug 1995 11:46:39 GMT Lines: 25 Xref: geraldo.cc.utexas.edu rec.audio.tubes:686 alt.guitar.amps:3262 In article <[email protected]>, [email protected] says... > >I realize that there were quite a few different transformers >used in Champ tube amps (the single 6v6 version). But has >anyone here had trouble running an 8 ohm speaker instead of >the 4 ohm standard? > >This should bring the primary impedance pretty high, presuming >Fender operates anywhere close to the normal load for a >6V6. In general, higher primary impedance should operate the >tube with less distortion...not nec. good for a guitar amp. > >Any experience or theories welcome. > >mg The five watts or so that the champ produces using the stock 5000 to 4 ohm transformer would be reduced. The distortion produced would be similar to driving a 4 ohm load although the 6V6 would dissipate less since the amount of AC current swing is less for the effective 10,000 ohm transformer impedance. The distortion would still be made by clipping the AC voltage swing which is limited by the amp's supply voltage. I have replaced a few champ output transformers due to primary winding overheating and open circuiting, so higher output impedances help a little. From [email protected] Thu Aug 31 22:07:09 CDT 1995 Article: 698 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!tank.news.pipex.net!pipex!newsfeed.internetmci.com!news.sprintlink.net!in2.uu.net!panix!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Running Champ with 8 ohms instead of 4 ohms Date: 31 Aug 1995 10:39:09 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 33 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com Xref: geraldo.cc.utexas.edu rec.audio.tubes:698 alt.guitar.amps:3266 In [email protected] (Mark Amundson) writes: >In article <[email protected]>, [email protected] says... >> >>I realize that there were quite a few different transformers >>used in Champ tube amps (the single 6v6 version). But has >>anyone here had trouble running an 8 ohm speaker instead of >>the 4 ohm standard? >The five watts or so that the champ produces using the stock 5000 to 4 >ohm transformer would be reduced. The distortion produced would be similar I was not sure that the primary was 4-5k. That's good to know. >to driving a 4 ohm load although the 6V6 would dissipate less since the >amount of AC current swing is less for the effective 10,000 ohm transformer >impedance. The distortion would still be made by clipping the AC voltage >swing which is limited by the amp's supply voltage. I have replaced a few >champ output transformers due to primary winding overheating and open >circuiting, so higher output impedances help a little. The Champ transformer does not look very rugged. Seems there's a relatively narrow band of usable speaker impedances. I would have guessed that 8 ohms would not be too far off, and would possibly help keep the primary cool. But Blackie's mention of arc'ing (adjacent messages) is a realistic concern. I have tried to contact Fender and some parts vendors to find out about failure modes for Champ (and other) output transformers, but no response yet. Regards, Mark G. From [email protected] Mon Sep 4 17:14:50 CDT 1995 Article: 3347 of alt.guitar.amps Newsgroups: alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!ix.netcom.com!netcom.com!rfries From: [email protected] (Robert Fries) Subject: Re: Running Champ with 8 ohms instead of 4 ohms Message-ID: Sender: [email protected] Organization: NETCOM On-line Communication Services (408 261-4700 guest) X-Newsreader: Forte Free Agent v0.38 References: <[email protected]> <[email protected]> Date: Mon, 4 Sep 1995 19:44:13 GMT Lines: 34 [email protected] (Stephen Delft) wrote: >Glass Audio 2/92 page 8 ( article on modifying a Fender Champ) >refers to a Fender #0024038 OPTX ; 5.1k to 7.5 Ohms. >In the article it is suggested for a Champ modified to take a 6L6, but >also seems to suggest that this would be a more robust alternative to >the regular 6V6 Champ OPTX, and has more bottom end. >Anyway, this might be one way of running a Champ into an 8 ohm >load with minimal loss of output. >What puzzles me is......this Fender stock part appears to be a >possible *alternative* for a regular Champ, but is not an exact >replacement. So what is it originally intended for ? >Is it an intended Champ upgrade, or did Fender at some time >make another "single-output-tube" amp which used this larger OPTX ? >Fender TX # 0024038 might be available from Magic Parts, but I haven't >received their new cat yet. > Cheers, Stephen. 024038 is the output transformer for the 'Champ 12'; which used a single 6L6. A couple of years ago, I ordered two of these from Fender. They sent the regular VIbroChamp transformer, 022905. They took so long to arrive, I jsut didn't bother with trying to straighten it out, and the Glass audio project got put on permanent hold for me. Which reminds me - does anyone need a 022905? I have two, I'll sell for $20 each. Robert Fries Champ Speakers From [email protected] Mon May 15 10:33:52 CDT 1995 Article: 51448 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!its.hooked.net!also.hooked.net!not-for-mail From: [email protected] (Kent Suzuki) Newsgroups: rec.music.makers.guitar Subject: Re: Good 8in Speakers to buy? Date: 14 May 1995 20:30:37 -0700 Organization: Hooked Lines: 31 Message-ID: <[email protected]> NNTP-Posting-Host: also.hooked.net [email protected] (Mark Garvin) wrote: > >>In <[email protected]> [email protected] >(Andy Warchol) >>writes: >>> >>> I'm interested in upgrading the speaker in a >silverface >>> Fender Bronco amplifier that I own. My problem is >that >>> it requires an 8" speaker, which I've not seen in >any > >Depending on the impedance, you could try one of the >Emminence spkrs avail thru New Sensor in >NYC.(212)529-0466. I think theirs are all around 4 >ohms. > >Mark Garvin I posted this info last week sometime, but I'll repeat it for this thread. I tried a few different 8" drivers for my VibroChamp, and the G8L-35 was THE ONE! It has a 4 ohm impedance, fits into the Champ without the magnet hitting the filter cap, and it has a tone similar to the original Fender speaker but beefier at higher volume. It's got nice top-end definition. Hope this helps. Kent From [email protected] Mon May 15 10:34:07 CDT 1995 Article: 51450 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!nntp.crl.com!decwrl!its.hooked.net!worm.hooked.net!notfor-mail From: [email protected] (Kent Suzuki) Newsgroups: rec.music.makers.guitar Subject: Re: Good 8in Speakers to buy? Date: 14 May 1995 20:43:51 -0700 Organization: Hooked Lines: 3 Message-ID: <[email protected]> NNTP-Posting-Host: worm.hooked.net Oops, I forgot to mention the G8L-35 is a Celestion speaker. THe other speaker I tried was the Celestion Vintage 8 (60W driver), and it was too muddy for that Fender tone. Kent Champ Transformers From [email protected] Mon Mar 1 22:16:33 CST 1999 Article: 162470 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.corridex.com!hub1.ispnews.com!news12.ispnews.com.POSTED!notfor-mail From: "Dean Yiapis" Subject: Re: Fender Champ PT/OT Newsgroups: alt.guitar.amps References: <[email protected]> Message-ID: <01be6453$79530660$5ea100d8@default> X-Newsreader: Microsoft Internet News 4.70.1162 Lines: 41 NNTP-Posting-Host: 216.0.161.93 X-Trace: news12.ispnews.com 920342133 216.0.161.93 (Mon, 01 Mar 1999 21:35:33 EDT) NNTP-Posting-Date: Mon, 01 Mar 1999 21:35:33 EDT Date: Tue, 02 Mar 1999 02:35:33 GMT Xref: geraldo.cc.utexas.edu alt.guitar.amps:162470 Short answer,Nope, sorry, it's like comparing apples to oranges. The specs on the Fender Champ x-formers are: Power Transformer; main sec. 650v @ 70mA heater 6.3v @ 2A heater 5v @ 2A Output Transformer; Primary 7000ohms Secondary 4ohms @ 8 watts If you want to construct a small amp with a "Plexi" type pre-amp and 2 EL-84 output tubes try the AX-84 project here; http://www.intsys.net/ax84/index.html Lots of good schematics. I think the one you'd be interested in is the "Moonlight" if I remembered the name correctly. At any rate, there is an ongoing discussion there about the amp projects, and some parts availability. -Dean And yet another person annoyed by spam, remove the not_here from my address to reply. Lajos Kamocsay wrote in article <[email protected]>... > Hello, > > Can I use a Fender Champ PT/OT to build a plexi like amp? > What outputs does the Fender Champ PT have? > > > thanks > > > > Champ problems From [email protected] Sat Jun 24 21:03:12 CDT 1995 Article: 50174 of alt.guitar Newsgroups: alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!nntp.crl.com!pacbell.com!gw2.att.com!oucsboss!cigna From: [email protected] (Dave Cigna) Subject: Re: Fender Champ Problem X-Nntp-Posting-Host: helios.phy.ohiou.edu Message-ID: Sender: [email protected] X-Nntp-Posting-Date: Sat Jun 24 16:26:22 1995 Organization: Ohio University Physics and Astronomy References: <[email protected]> <[email protected]> Date: Sat, 24 Jun 1995 20:26:23 GMT Lines: 39 In article <[email protected]>, Steven Milberger wrote: >Try replacing the rectifier with an American made 5V4GA >instead of a Sovtek 5Y3. A used American tube is most >always better than the Sovtek equivalent. Weber's book >explains why the 5V4 is better than the 5Y3. [...] My opinion of Weber is that he's too opinionated when it comes to rectifier tubes. He almost universally recommends replacing whatever rectifier happens to be in your vintage Fender with whatever tube he happens to find with lower losses (higher resultant voltages.) This will make most amps tighter and brighter, but the fact is many people prefer the browner, more compressed tone of the correct tube that ol' Leo specified. Weber was probably refering to tweed Champs anyway, since blackface Champs are running respectable voltages as it is and silverface Champs are already TOO HIGH. This means that the silver ones have a little less warmth and sweatness already and using a 5V4 rectifier will only make them colder. (Incidently, you can lower the voltages of silver Champs to blackface levels by installing a 10 (or more) watt, 1000 ohm power resistor between the rectifier and the first filter cap. email me if you'd like more details.) > >BTW, does anyone out there know if the Champ need to be >rebiased when changing the 6V6 tube? I didn't see a bias >pot so it must be fixed biased? They're cathode biased and I've never known it to be necessary to rebias them, though you can tweek the tone a little that way. One note is that the cathode resistor on blackface Champs is usually underated at 1 watt. I sometimes replace them with 2 watt metal oxide pieces. More importantly, the bypass caps on almost all Champs are underrated at 25 volts. To make matters even worse, the resistor is usually mounted right on top of the capacitor thus overheating it. I recommend replacing the bypass cap with a fresh 25uF/50V unit and separating the resistor and cap as much as possible. -- Dave Cigna Choke Specs From [email protected] Tue Dec 24 08:44:24 CST 1996 Article: 31922 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!worldnet.att.net!uunet!in2.uu.net!206.58.0.35!news.structured.net!nntp0.teleport.com!usenet From: "Zack Engineering" Newsgroups: alt.guitar.amps Subject: Re: DeLuxe Rvb Filter Choke Spec Date: 24 Dec 1996 07:49:17 GMT Organization: Zack Engineering Lines: 24 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ip-pdx05-07.teleport.com X-Newsreader: Microsoft Internet News 4.70.1155 [email protected] wrote in article <[email protected]>... > Does anybody have the specs (Henries, resistance) for the filter choke in > a BF Fender Deluxe Rvb (AB763)? Mine arcs when you tap on it, and want to > get it replaced ASAP. Also a source for a replacement would be > appreciated. > Thanks. > Kevin, It was a MisPrinted Filter Choke Spec I bought a LX meter to measure inductance and then measured all of our TF-150 chokes and both the Fender #036486 and #022707. Even though my supplier said it was not a misprint, it was. All of the #036486 chokes measured 3 Henrys and all of the #022707 chokes measured 4 Henrys. So, go ahead and put it in your Deluxe Reverb. I have corrected my website to reflect this news, so there won't be problems in the future. BTW: If you desire the original Fender part# 022707 let me know and I will Quote you a price. I'm sure it is more$$ just for the Fender Name. Thanks, it gave me a good excuse to go buy the LX meter. Zack, [email protected] http://www.vibroworld.com/~vibroman Clean Ckt Board From [email protected] Fri May 26 15:46:32 CDT 2000 Article: 253181 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsfeed.skycache.com!Cidera!205.212.123.11!cletus.bright.net!notfor-mail From: JER Newsgroups: alt.guitar.amps Subject: Re: Funky or conductive Fender eyelet boards Organization: JER Message-ID: References: X-Newsreader: Forte Agent 1.8/32.548 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 19 Date: Fri, 26 May 2000 15:10:41 -0400 NNTP-Posting-Host: 209.143.13.91 X-Complaints-To: [email protected] X-Trace: cletus.bright.net 959368094 209.143.13.91 (Fri, 26 May 2000 15:08:14 EDT) NNTP-Posting-Date: Fri, 26 May 2000 15:08:14 EDT Xref: geraldo.cc.utexas.edu alt.guitar.amps:253181 On Fri, 26 May 2000 15:31:58 GMT, "BK" wrote: >Has anyone ever had a Fender "bleed", or couple, normal channel signal into >the reverb driver ckt.? >I have one that IS doing it! With a thorough scrub-job, I have all but >eliminated it. Any ideas besides removing the board entirely (to clean >under-side) for a total fix? > >Thank you, > >Bill > Remove the three screws holding the eyelet board and the insulating board. Then you can slide the insulating board out at the transformer end of the amp. You can now pull the eyelet board up enough to get a tooth brush soaked with solvent under it. Works for me. --Jack From [email protected] Fri May 26 15:47:00 CDT 2000 Article: 253188 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.gtei.net!news.maxwell.syr.edu!nntp2.deja.com!nnrp1.deja.com!not-for-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Funky or conductive Fender eyelet boards Date: Fri, 26 May 2000 19:38:27 GMT Organization: Deja.com - Before you buy. Lines: 36 Message-ID: <[email protected]> References: NNTP-Posting-Host: 167.128.140.206 X-Article-Creation-Date: Fri May 26 19:38:27 2000 GMT X-Http-User-Agent: Mozilla/4.72 [en] (Win98; I) X-Http-Proxy: 1.0 x55.deja.com:80 (Squid/1.1.22) for client 167.128.140.206 X-MyDeja-Info: XMYDJUIDsimply_steve Xref: geraldo.cc.utexas.edu alt.guitar.amps:253188 In article , "BK" wrote: > Has anyone ever had a Fender "bleed", or couple, normal channel signal into > the reverb driver ckt.? > I have one that IS doing it! With a thorough scrub-job, I have all but > eliminated it. Any ideas besides removing the board entirely (to clean > under-side) for a total fix? > > Thank you, > > Bill My 68 DR had crackle and hiss in the reverb circuit that wound up being for the most part caused by the fiberboard. You don't have to completely remove it but you do have to disconnect enuf wires from one edge to get at the bottom, and yes, you DO need to scrub the bottom and the second board underneath, too. Cleaning just the top just warshes an aweful lot of the crap underneath. My 75 VR had a real LOUD ticking in the vibe ckt (not the "normal" ticking, I mean way LOUD) that was due to contamination of the board, too. In this case it wasn't as dirty but had a full assload of wax on the board, melting most of the wax off with a hairdryer and presumably evaporating trapped moisture cured that one. So the basic answer is yes, I've seen not the same exact symptom, but the same causes on both my Fender amps. What are you using to clean with? Steve Sent via Deja.com http://www.deja.com/ Before you buy. From [email protected] Fri May 26 15:47:05 CDT 2000 Article: 253190 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsout.worldnet.att.net.MISMATCH!wn3feed!worldnet.att.net!wnmasters3!bgtnsc06-news.ops.worldnet.att.net.POSTED!not-formail From: "BK" Newsgroups: alt.guitar.amps References: <[email protected]> Subject: Re: Funky or conductive Fender eyelet boards Lines: 15 Organization: FMI X-Newsreader: Microsoft Outlook Express 4.72.3612.1700 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3612.1700 Message-ID: Date: Fri, 26 May 2000 19:59:51 GMT NNTP-Posting-Host: 12.76.74.55 X-Complaints-To: [email protected] X-Trace: bgtnsc06-news.ops.worldnet.att.net 959371191 12.76.74.55 (Fri, 26 May 2000 19:59:51 GMT) NNTP-Posting-Date: Fri, 26 May 2000 19:59:51 GMT Xref: geraldo.cc.utexas.edu alt.guitar.amps:253190 >What are you using to clean with? "Tun-o-wash" from Chemtronics. It's a gen. purpose non-residual cleaner/ de-fluxer that they use in the lab. here at work. bill > >Steve > > >Sent via Deja.com http://www.deja.com/ >Before you buy. Concert Head Footswitch From [email protected] Mon Oct 27 11:59:16 CST 1997 Article: 68542 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!newsfeed.direct.ca!news.uunet.ca!cajun From: [email protected] (JP) Newsgroups: alt.guitar.amps Subject: Re: Fender Concert head footswitch Date: Sun, 26 Oct 1997 11:55:03 GMT Organization: UUNET Canada News Transport Lines: 50 Message-ID: <[email protected]> References: <01bcd84a$15cd8020$94bb89d0@default> <[email protected]> NNTP-Posting-Host: 205.205.27.168 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Newsreader: News Xpress 2.01 Xref: geraldo.cc.utexas.edu alt.guitar.amps:68542 In article <[email protected]>, Monika La Badie wrote: > > >Robert Eames wrote: > >> I just bought an early 80's Fender Concert head. The footswitch was >> missing. I'd like to get one for it. Are they easy to come by? On the >> back of the head, there's a pedal hot and pedal plain inputs. Anybody have >> any ideas? Thanks in advance. > You Can make one yourself, using the following parts: 2 x 1/4" stereo plugs (+ cables), 2 x 1/4" stereo jacks, 1 x dual color LED (Green, Red), 1 LED (Green), 2 x 510 ohm resistors and 2 x DPDT swithches. The circuit is as follows: Connections are stereo 1/4" RED Jack: Tip - -6.2 Volts Ring - Channel 1 (Hi Gain) Gnd - ground shield PLAIN Jack: Tip - Channel 2 (Clean) Ring - Reverb Gnd - ground shield -6V attaches to the cathodes of two LEDs. RED/GREEN for Channel and GREEN for Reverb. Gnd attaches to the common lugs of the two DPDT switches and the box. Anodes of two LEDs attach to 510 ohm resistors. Channel Switching: GREEN LED resistor attaches to DPDT lug that goes with Channel 1. RED LED resistor to DPDT lug that goes with Channel 2 . Reverb Switching: Green LED resistor attaches to DPDT lug opposite the Reverb lug and ground. (When Reverb is grounded, it's off) so this is an On/Off thing -- Jp -- ____________________________________________________________ To Reply E-Mail you must remove the "No.Spam" from my E-mail address Dead Amp Checkout From [email protected] Wed Feb 4 15:55:13 CST 1998 Article: 83914 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!cpk-news-hub1.bbnplanet.com!su-newshub1.bbnplanet.com!news.bbnplanet.com!news.alt.net!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: DR dead... Date: 4 Feb 1998 09:09:10 GMT Organization: Netcom Lines: 47 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: den-co13-11.ix.netcom.com X-NETCOM-Date: Wed Feb 04 1:09:10 AM PST 1998 Xref: geraldo.cc.utexas.edu alt.guitar.amps:83914 In <[email protected]> [email protected] (Myoshi3) writes: > >OK, I know someone can help me out here! My SF DR (late model with the >push-pull volume boost standard) has just died on me. There is no output at >all. The tubes still light (nice healthy red glow with a bit of blue on the >center beam), the pilot light still lights, but nothing comes out... Not even >the usual 60hz hum that I've grown to love. Anyone know what this might be? > >Thanks in advance, >Mike Lord Valve Speaketh: Well, if you have blue in the power tubes, you have B+. Orange means you have filament voltage, also confirmed by the fact that the pilot lamp is lit. I'm assuming you've tried to play through both channels, and that neither worked. So...possible problems, in order of likelihood: 1) Open speaker wire. (Broken, or disconnected from terminal.) If you find that this is the problem, check the power tube sockets for arc tracks between pins two and three. If you see any, you MUST replace the socket, AND THE TUBE THAT'S IN IT. This may show up on either side of the socket, so you'll have to take a peek inside the amp to be sure. 2) Open voice-coil. (Also check the sockets as above.) 3) Shorted speaker wire. (This will knock all the hum off the output, but if you play with the amp turned way up, you'll still be able to hear a little bit of very fuzzy-sounding output from the speaker.) 4) Bad phase-inverter tube. This is the 12AT7 right next to the power tubes. 5) Shorted output transformer secondary. It'll give the same symptoms as #3. 6) Open output transformer secondary. Again, check the sockets for arcing. 7) This might sound stupid, but I've seen it many times. Check to see if the speaker wire is plugged into the "SPEAKER" jack, and NOT the extension speaker jack. If that is the case, it'll give the same results as #3. Lord Valve Website at: http://www.freeyellow.com/members2/lord-valve/ "I got the chop...I'll never get popped." - Tower of Power Deluxe Cathode Bias Mod From [email protected] Tue May 21 07:40:21 CDT 1996 Article: 9985 of rec.audio.tubes Newsgroups: rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!natinst.com!newsrelay.us.dell.com!swrinde!newsfeed.internetmci.com!in2.uu.net!netnews.worldnet.att.net!cbgw2.att.com!oucsboss!cigna From: [email protected] (Dave Cigna) Subject: Re: zener diode for dropping B+ X-Nntp-Posting-Host: helios.phy.ohiou.edu Message-ID: Sender: [email protected] X-Nntp-Posting-Date: Mon May 20 13:23:17 1996 Organization: Ohio University Physics and Astronomy References: <[email protected]> Date: Mon, 20 May 1996 17:23:19 GMT Lines: 44 JER wrote: >I would be interested in the details of the cathode bias. Can you give us >a full discription of the *full* mod? For cathode bias, I'm using a 590 ohm, 25 watt resistor shared by both tubes. I chose this value because I happened to have the resistor. :) You could probably go as low as 500 ohms, especially if you're reducing the supply voltage, but 590 seems to work pretty well. The resistor is bypassed with a 100uF/100V electrolytic cap. To install: remove the ground straps that connect the cathode pins on the tube socket to the chassis. You can remove them from just the tube socket if you want to be able to reverse the mod easily, but you *must* make sure that the loose ends are well insulated. If one of them touches the cathode pin on the tube socket your precious 6V6s could be ruined in an instant. A piece of shrink tubing over the strap might do the job. Connect both of the cathodes together with hookup wire and connect the resistor between one of them and ground. Be sure the resistor has a high enough power rating -- *at least* 10 watts. I like the aluminum cased jobs that you can buy from Mouser. I found an existing hole in the chassis that worked well to bolt to resistor down. I connected the ground end of the resistor to the same ground point as the filter caps and soldered the bypass cap right across the resistor with as much space between the two as possible. The heat from the resistor is not good for the cap, but it's a little cramped inside the chassis with heat sources everywhere. After some consideration I decided this was the best option in this case. Remember to put the '-' end towards ground. Now you need to remove the grids from the fixed bias supply and provide a path to ground: there is a wire going from the junction of a pair of 220k resistors to the tremelo 'intensity' control. Remove this wire from the intensity control and solder it to a good ground connection. The trem will no longer work (sorry). That should do it. Connect a voltmeter across the new cathode resistor and turn the amp on while watching the meter. The voltage should rise to 25-30 volts as the heaters warm up. If it doesn't, or if your output tubes get red, shut the power off and check your work. I described the zener mod in a previous post. If you need more details you can email me. -- Dave Cigna Deluxe Tweed vs BF From [email protected] Wed Sep 13 14:48:36 CDT 2000 Article: 275180 of alt.guitar.amps Path: geraldo.cc.utexas.edu!newsfeed.cs.utexas.edu!hammer.uoregon.edu!newsfeed.direct.ca!look.ca!newshub2.rdc1.sfba.home.com!news.home.com!enews.sgi.com!nntp.msen.com!nntp1.savvis.net!nntp4.savvis.net!nntp2.savvis.net!nwnews.wa.com!news3.nwnexus.com!baraddur.nas.com!mschway From: Mike Schway Newsgroups: alt.guitar.amps Subject: Re: Tweed vs Blackface Deluxe Date: Tue, 12 Sep 2000 09:21:27 -0700 Organization: entropy tends to increase Lines: 48 Message-ID: References: <[email protected]> NNTP-Posting-Host: c224737-b.frndl1.wa.home.com X-Trace: barad-dur.nas.com 968775642 61546 24.14.226.82 (12 Sep 2000 16:20:42 GMT) X-Complaints-To: [email protected] NNTP-Posting-Date: 12 Sep 2000 16:20:42 GMT User-Agent: MT-NewsWatcher/3.0 (PPC) Xref: geraldo.cc.utexas.edu alt.guitar.amps:275180 Tweed deluxe: 12-14W clean (depending on output tranny, it can push up to 20+ W with distortion). Much less clean headroom, but sounds great when pushed. Volume control goes up to "12", but it really starts breaking up around 2 1/2 even with single coil pups. Above 6 or so, there's not really much difference in volume. Single tone control with a fairly dark, smokey tone. Tone control needs to be around 8-9 (out of 12) before amp sounds at all bright (but it never gets as sparkley as the BF). Of course speaker choice will influence the tone a whole bunch. Can be pushed into glorious overdrive without your neighbors calling the cops. Still with the right output tranny and speaker, it'll sound just as loud as the BF when pushed hard in a club situation. Blackface deluxe: Brighter, snappier tone. 20-22W clean (up to 25W w/distortion). Usually comes with reverb & tremolo (they call it vibrato, but it ain't). Separate bass and treble tone controls for a bit more variation in tone, but really it's a cleaner-sounding amp until you push it hard (around 6 out of 10 on the volume pot). When played clean, the DR sounds remarkably like the twin (though at lower volume). Reason: nearly the same tone circuit (no MR control on the DR). Sounds wonderful when pushed, tho not exactly at living-room volumes. It's really up to you. Personally, I prefer the sound of the tweed with my tele, even when played in the clean range (which is really, really narrow). I've built clones of both types (a non-reverb BF head and a 5E3 complete with tweed box), and owned a real '67 DR, and they both have their own merits. I just happen to prefer the darker 50's tone. --Mike Schway In article <[email protected]>, [email protected] wrote: >I am in the market for a smaller amp (I have a real 1965 blackface Twin >Reverb), and am >considering a Deluxe. Any opinions regarding tweed vs blackface deluxes >for overall tone? >Also, are the reverb-equipped tweed clones by Victoria or Clark >recommended, or should I >stick to the original design and use a reverb device with it? I would like >to play the amp >cranked for classic blues/rock tone. This will be for home/jamming/small >club >applications. I want the best tone possible. Recommendations? > -------------------------------------------------------------------Mike Schway | [Picture your favorite quote here] [email protected] | -------------------------------------------------------------------- From [email protected] Wed Sep 13 14:49:06 CDT 2000 Article: 275287 of alt.guitar.amps From: "David Kieltyka" References: <[email protected]> Subject: Re: Tweed vs Blackface Deluxe Date: Tue, 12 Sep 2000 23:49:45 -0400 Lines: 29 X-Newsreader: Microsoft Outlook Express 4.72.3155.0 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3155.0 Message-ID: Newsgroups: alt.guitar.amps NNTP-Posting-Host: chi-tgn-gvr-vty18.as.wcom.net 216.192.151.18 Path: geraldo.cc.utexas.edu!newsfeed.cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.gtei.net!newsfeed.cwix.com!cpmsnbbsb04!cpmsnbbsa09 Xref: geraldo.cc.utexas.edu alt.guitar.amps:275287 Mike Schway wrote: > Volume control goes up to "12", but it really starts breaking up > around 2 1/2 even with single coil pups. Above 6 or so, there's > not really much difference in volume. Single tone control with > a fairly dark, smokey tone. Tone control needs to be around > 8-9 (out of 12) before amp sounds at all bright (but it never > gets as sparkley as the BF). Of course speaker choice will > influence the tone a whole bunch. What speaker do you have in your Deluxe? I'm wondering because I can get more clean headroom and high end out of my Deluxe (a '60) than you describe. I have a WeberVST P12R in mine, and also have the original Jensen P12R too. I like 'em both a lot. The Weber is snappier than the Jensen (which, granted, has seen *lots* of use). If I plug into the Instrument channel with its volume at 6 and the Microphone channel's volume at 12 I get a real nice, lively clean sound with my Tele. This de-emphasizes the mids. It's not loud enough for gigging but dandy for recording. Now if I turn down the Mic channel to around 9.5 the mids come forward and the volume just about doubles. Sweet & dirty. Turning up the Instrument channel further adds more dirt and saturation. With the Tele I keep the amp's tone control between 4 and 6. This gives me a twangy high end without any trace of ice-pick treble. Until recently I've always used RCA black plate 6V6s in this amp. Currently, though, I have a set of Mazdas installed...great tone, right up there with the RCAs IMO. -Dave- Deluxe reissue vs original From [email protected] Wed May 1 13:39:49 CDT 1996 Article: 14103 of alt.guitar.amps Path: geraldo.cc.utexas.edu!ausnews.austin.ibm.com!newsm01.ny.us.ibm.net!newsjunkie.ans.net!newsfeeds.ans.net!news3.ottawa.istar.net!istar.net!news1.vancouver.istar.net!news.vancouver.istar.net!west.news.istar.net!vanbc!ddsw1!news.mcs.net!usenet From: Teleologist Newsgroups: alt.guitar.amps,rec.audio.tubes Subject: Re: resistors - carbon vs. metal Date: Wed, 01 May 1996 09:49:24 -0500 Organization: MCSNet Internet Services Lines: 47 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: alsnt.image.ctt.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0 (WinNT; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:14103 rec.audio.tubes:9176 Robert Fries wrote: > > James Lane wrote: > > >mr teleologist, > > >what speaker, tube, bias combination would you recommend for the deluxe > >reissue? They come stock with jensen 12" and fender tubes. > > >Thanks in advance for the info. > > >-James > Didn't see the original post from Jim - Bob is correct about the Eminence speaker, tubes etc. The Eminence 12" speaker is a little weird as it has the deep cone angle & small dust cover like the old P12 alnico Jensens, but with a BIG ceramic magnet. IMO it sounds decent in the pseudo tweeds, but lacks bass response & punch while 'razor-blading' your ears in the BF circuits. The C12 series Jensens have a shallower cone angle & a bigger dust cap which produce more bottom and a less tightly focused top end. Although not commonly shipped in the Deluxe Reverb I like(and have) an original cone C12Q. This version has a larger magnet, a 1/4" bigger voice coil, and IMO handles modern 'cranked up' power levels better than the usual C12R. Tremolux has posted that some guys are using P12Ns or Ps in Deluxe Reverbs & loving the results - Haven't tried that....yet! The amps I AB'd were my own '66(bought new in '66!) & a 1st year reissue(93?) using the C12Q in my amp & also a JBL D120F in a repro Deluxe extension cab. As I recall tubes at the time were an Amperex or Mullard GZ34/5AR4, Sylvania 6V6GTAs, & Phillips/Sylvania 12AT7s & 12AX7s. The same set of tubes were swapped in the same positions from amp to amp. My amp's 'sweet spot' happens with the tubes biased between 24 & 25ma per tube with about 417-418 B+(about 413 on the plates). All voltages were consistent bewteen the 2 amps. Each amp was recorded to digital 3 ways(direct plus 2 mikes) with clean & distorted sounds from different guitars & 2 different players(no EQ tweeking on the board BUT settings on the amps were different - pot tapers are different so this isn't a pure scientific test...we were curious!). The tapes were AB'd thru headphones, nearfield monitors, & upgraded JBL 4311Bs and it was difficult(but possible) to tell them apart! The oldie had a little more compression & a slightly mellower top end. With a RIC-12 clean using the D120F, higher frequency harmonics seemed to bloom better on the oldie but were definately present with the reissue. (BTW Both amps sounded like ____ using the reissue speaker!) A friend has a reissue Twin Reverb which received a pair of JBL E120s & Sylvania STR 415s. For the very few live gigs I play I usually rent a favorite BF Twin Reverb & these 2 amps compare fairly well despite differnt speakers etc. Design Eras From [email protected] Tue Aug 25 10:35:30 CDT 1998 Article: 123410 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer.sprintlink.net!news.sprintlink.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] (LarrySB) Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Lines: 49 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Date: 25 Aug 1998 03:23:09 GMT Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:123410 <<< Can someone point me to any on-line photos so I can see the differences and perhaps come sort of chronology? >>> Hmm, I see you are outside the states. I'm only saying so because some idiot will pop-off not knowing that there are other countries on the planet. The historical and cosmetic distinctions coincide. Each major change in Fender's amp design was generally accompanied by a change in cosmetics. There are MANY books you can find that cover the history of Fender and guitar amps. One source of some pictures and LOTs of schematics are the Groovetubes amp book and Gerald Webers Hip Amp reference. Other books aren't as technical, but have lots of pictures and history. Anyhow, the Fender amp era's go like this: tweed - so named because they were covered with a tweed like fabric, which fender called "luggage linen." 1948-1960 brown - these were the first amps with upside down chassis and controls up front. Usually covered with brown tolex (vinyl cloth), though some had cream colored too. blackface - these tend to be the most commonly discussed. They were covered with black tolex, and the control panels were painted black. These amps sported sophisticated electronics and tone controls, most models came with vibrato effect and many models came with reverb as well. 1964-1967. silverface - most models were the same as the blackface models, but a number of engineering changes heralded these models. The front panels were bright aluminum. Over their run, the silver era saw a lot of changes mostly to squeeze out more power. Mostly reguarded as players, they are built well, and most of them can be modded to BF era schematics, if the owner so chooses. 1967-1980. This was the end of hand-wired construction. After 1980, Fender re-introduced the BF era cosmetics, came out with the much hated "red-knobs", and played around with different types of cosmetics. Today, they make amps on PC boards, which sound OK, but will probably not hold up after years of road use. So, there you go. -Dr. Nuketopia Compiling at this very moment. Read the Blue Glow in Tubes FAQ at http://www.persci.com/~larrysb Please note that your email is *not* spam in the subject line. Detailed AB568 test From [email protected] Sat Jan 11 13:41:58 CST 1997 Article: 34038 of alt.guitar.amps Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.io.com!fnord!news.thenet.net!news1.best.com!www.nntp.primenet.com!nntp.primenet.com!nntp.uio.no!newsfeed.inet.tele.dk!news.algonet.se!hammer.uoregon.edu!news-xfer.netaxs.com!panix!news.panix.com!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: My SF-BF experiment Date: 11 Jan 1997 07:47:47 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 279 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com > Scott Hinman writes: >The experiment: stepwise conversion of my silverface to > blackface specs. Hi Scott, Thanks for taking the time to do such a meticulous job and for posting the results! And compliments to Kathy with the golden ears! (Really! She could reliably tell the difference between grounded cathodes and bypassed 150 ohm resistors? I'm impressed!) I've spent lots of hours trying to answer tech questions on a.g.a., and once in a while it actually seems worthwhile. I'll try to explain some of my own thoughts on the Fender circuit. Maybe this will help to put your test results in perspective. >The amp: Early '69 Pro-Reverb (all the pots are 68 except for one 69). > >The guitar: (Well, someone might think its relevant). 76 Gretsch > superaxe. The pickups are Gibsons, don't know what Actually could be relevant to high frequency content. Good to know. >Step two: Install three wire cord with ground to chassis. Good! I should remember to suggest this more often. >Step three: Added a second bias adjustment pot in parallel with > existing one to allow individual bias adjustment of > each power tube. (Not in BF circuits, but I thought > it was a good idea anyway). Another good addition. I'm surprised more boutique amps don't do this. >Step four: Replace the plate resistors in the phase inverter circuit > from the 47k / 47 k SF values to 82 k / 100 k BF values. > Also changed the 100k bias feed resistors to the 220k > BF values. Reinstall chassis in amp, and play. > >This is the least scientific of the tests I did, since I couldn't >quickly go back and forth between the BF and SF phase invertor >circuits. The effect of the change was small, if any. At the time >I wrote "I think its a little louder. It seems to be a bit cleaner, Mathematically, this change should not make a huge difference in gain with a 12at7, though I've heard a fairly pronounced difference sometimes. I wrote a computer program to model the gain equation for that circuit with various tubes and component values. Some of the results are surprising. Here's something interesting about that circuit: Though the 12at7 has lower 'Mu' than a 12ax7, it can actually have higher overall gain in Fenders with the 47k/68k circuit. The Mu is sometimes thought of as being synonymous with gain, but that's not exactly true. Mu is transconductance times plate resistance. Sorry that I can't explain in depth, but when driving low impedances (like the 47k/68k resistors in parallel), the lower plate res of the 12at7 works in its favor. Tim Tube made some interesting comments regarding sound of 12at7's vs 12ax7's as phase inverters recently. The general idea is that 12at7's are better drivers, and the lower plate resistance can help to avoid treble loss due to local capacitance. (more later) >Step 5: Changed the resistor values in the power supply chain. > In my amp, they went choke to 4.7k to 10 k, and in the > BF circuits (and seemingly all the SF circuits except > the AB 668) they go choke to 1k to 4.7k. > >This should change the plate voltages to both the preamp and phase >invertor. If there was any diffence in sound from this, though, >it was completely inaudible to me. Agreed. May change the headroom a bit. May eliminate a bit of supply sag, too. >Step 6: Take a box with 8 SPST switches in it. (Just happened to > have one). Rig it to be able to a) switch the existing > 2000 pF grid capacitors (not present in BF circuits) either > in or out of the circuit. b) switch the non-polarized cap > (also a SF addition) coupling the two power tube cathodes > in or out of the circuit, and c) switch two 220uF caps into > the circuit from the power tube cathodes to ground > - thus shunting the SF 150 ohm cathode resistors. > (These caps aren't BF entities, they were suggested > by Mark Garvin - more on his reasoning later) > >This is where I'm going to get accused of having tin ears. Not by me, though my own test results may have been a bit different. >First, neither Kathy nor I could hear any difference whatsoever >on taking the 2000pF grid caps out of the circuit. We went >back and forth several times - and notta. You can even switch >while playing a sustained chord, and there ain't no difference. Recently both Tim Tube and Fat Willie agreed (Eek!) that there would be a big difference when doing this. Nostradomas warned that the alignment of opinions of Tim and Willie were one of the signs of the end of the world, but we'll ignore that for now. The aforementioned 12at7 should have a plate resistance of around 10k or so. The theoretical corner frequency (point where highs start rolling off by -3db) can be calc'd as: f = 159000 / (C * R) where C is in microfarads. So the 'RC' (resistor/Capacitor) filter in this case has a corner at: f = 159000 / (.002 * 10k) the 10k is the plate resistance. so.... f == 8000hz Highs start rolling off at 8Khz...pretty high! Note that a 12ax7 has a plate res around 62K ohms, so changing the phase splitter tube could make a big difference, though the plate load res's would also start figuring into the equation (they would be paralleled with the plate resistance), so the value would be around 35k to 40k. With hifi/stereo gear, the 8Khz range is indeed audible, but most guitar speakers are not putting out much sound up there. They start to roll off sharply around 5Khz. Another thing to keep in mind is that fuzz boxes and overdrive preamps can sound really harsh if the high end is over-accentuated. Given that the equations above are pure paper (in this case computer screen), they are not always to be believed, but my own listening tests confirm your opinions. Yes, once in a while I actually disagree with Tim! But that's what keeps things interesting. You also mentioned that you were testing with humbuckers. This could also have some bearing, and the particular speakers in your amp, etc. >Next, switch the cathode coupling cap out of the circuit, and the >two 220uF shunt caps into the circuit. BIG DIFFERENCE here. >Kathy's words "It just sounds more focussed". At lower volumes >the highs stood out more, and the bass seemed less muddy. Definitely I have to admit that I'm surprised that you noticed that BIG a difference here, though I expected some change. And I expected it to be more noticeable at high volumes. However, I've always thought that the cap bypass method (rather than the resistors themselves) was the main problem with this circuit. Here's why...a bit of background first: Class A cathode biased amps usually hook the two cathodes together and provide a single resistor from their junction to ground. The shared resistor provides a set amount of current to both output tubes. Since the tubes operate in push-pull, when one starts to conduct more, the other starts to conduct less: a seesaw effect. There is no need to bypass the resistor because the current thru it does not change. This works fine until one of the tubes turns off completely (this means that the output circuit has gone into class AB). Kinda like one end of the seesaw hitting the ground--no more seesaw effect. The other tube is trying to pull more current, but now it must pull it thru the cathode resistor cause there is no more 'give' from the other tube. So from the point where one of the tubes turns off, the cathode resistor will 'enter the circuit' and will limit current thru the other tube. Bypassing the cathode resistor with a large cap solves the problem, as it provides a low impedance AC path around the cathode resistor. That's why class A amps with shared cathode resistors do not need cathode bypass caps. Class AB amps do. Now for the Fender circuit: Consider what the non-polarized (np) cap is doing in the normal Fender circuit: it provides a virtual short between the cathodes, but *just for ac signals* (caps block DC). So imagine what the circuit would look like if you shorted the two cathodes together: Just like the class A circuit described above! The problem, of course, is when the output circuit goes into class AB (when the volume is cranked). Same thing happens as described with the class A amp above. Another problem is that the value of the cap that Fender used is too small to bypass low freq's effectively. So at low frequencies, the 150 ohm resistors will limit current. And that's why I suggested using the two separate, large-value bypass caps in your experiment. >Step 7: Rig the switches to short the power tube cathodes directly > to ground, shunting the now parallel combinations of 150 > ohm resistors and 220uF caps. [and correcting bias] > >We spent a long time evaluating this one. I honestly couldn't >tell any difference between shorting the cathode resistors directly >to ground, or shorting them with the 220 uF caps. At low volumes, >Kathy said she thought it sounded better with the 220 uF caps handling >the AC, as opposed to the direct to ground connection. While she >couldn't explain to me what "better" meant, she did seem to be able >to pick out the same configuration as better, even when I was running >the switches and she couldn't see them. Then, when I cranked it up, >she identified the _other_ configuration, with direct shorts from >cathode to ground, as "better", and seemed to be able again tell the >difference even when she couldn't see the switches. To me, there >was no difference. (Again, grid caps made no difference in or out). I would expect very little difference there. Good for Kathy if she could tell! There will be a bit of difference in operation, esp. as the circuit is played louder. Some do like fixed bias better than cathode bias. This circuit (with switches open) would be partially cathode biased, so maybe that's what Kathy was picking up on. >The rational between using the 220 uF caps and leaving the cathode > resistors in is from Mark Garvin, who wrote in aga not long ago: >>I may have mentioned this in the past, but cathode resistors help to >>relax the grid-dc-res-to-ground spec of output tubes. They help to >>keep tubes from 'going gassy' due to ionization when the grid resistors >>are high (which they are, at 220k). So...it would be great if the >>Webernoia regarding the cathode resistors could be confirmed (as >>opposed to sonic diff's due to phase splitter and bias res values). >>I'd still love to hear a logical explanation for why mixed cath/fixed >>bias is a bad thing. Either bias method sounds fine alone, right? Your experiments and my own would seem to confirm this, Scott. I'm not sure exactly how much the low-value cathode resistors would relax the constraint on the DC-grid-to-ground spec, so you may not be gaining much by leaving the resistors and large caps in there. >(P.S. gonna put a sticker in the speaker cab, > -BF'd with a little help from aga-) Thanks again for following through and posting such detailed results, Scott (and Kathy)! I didn't want to post any lengthy explanations until you finished your test. I hope this post helps to make sense of what you were hearing. I'd still like to resolve why you heard such a big difference between the standard Fender circuit and the version with large bypass caps at higher frequencies and lower volumes. The highs should have been bypassed even by the low value np cap. And in fact, I didn't hear a *pronounced* difference when I tried this. It would also be great to find out what the difference is with Tim's and FW's amps/speakers/guitars that would make the .002's so audible. Over the years I've been trying to resolve situations where listening tests do not agree with mathematical results. It has always turned out to be an oversight in the mathematical model. Usually an educational experience. Mark Garvin From [email protected] Sat Jan 11 13:42:15 CST 1997 Article: 34069 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!feed1.news.erols.com!news.bbnplanet.com!cpk-newshub1.bbnplanet.com!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: My SF-BF experiment Date: 11 Jan 1997 19:14:10 GMT Organization: AOL http://www.aol.com Lines: 23 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] X-Newsreader: AOL Offline Reader In article <[email protected]>, [email protected] (Mark Garvin) writes: > >It would also be great to find out what the difference is with >Tim's and FW's amps/speakers/guitars that would make the .002's >so audible. > > Thanks for the all the leg work and consise reporting Scott. Thanks for the review Mark. Generally the first thing I do when I see those .002 caps is snip them. To me, it is just like turning up the tone control on the guitar a notch. If you turn up the amp and just listen to the air noise, you should certainly be able to hear a difference when you A/B test. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. Dr Z Harp Amp Mods From [email protected] Fri Feb 7 10:31:05 CST 1997 Article: 37595 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!www.nntp.primenet.com!nntp.primenet.com!news.maxwell.syr.edu!insync!uunet!in2.uu.net!152.163.170.17!newstf01.news.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] (MZaite) Newsgroups: alt.guitar.amps Subject: Re: Harp amp mods Date: 7 Feb 1997 01:34:01 GMT Organization: AOL http://www.aol.com Lines: 17 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] If you are using a Fender Blackface or Silver as your test bed, try one with a 2 output tube set-up. 1) replace the 1M on the 1st input jack with a 5M resistor. 2) replace that channels 100K plate resistor with a 470K 3) replace the 1.5K cathode res. with a 2.7K, and leave the 25/25 bipass cap in place. 4) decouple the stage with a .047 uF. 5) decrease slope res. from 100K to 56K 6) replace the Phase Inverter 12AT7 with a 12AX7. 7) If it has a tube rectifier, try a big bottle 5U4 8) here comes the BIG one install 6V6's to replace the 6L6's, and install a dropping res. of high wattage to lower the screen voltage, say 500 ohm 10 watt. 9) set the bias to 27mA / tube . 10) plug in and give it a blow. Later DR.Z Early Blackfacing From [email protected] Fri Sep 4 13:03:01 CDT 1998 Article: 125034 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.iag.net!newsspur1.maxwell.syr.edu!news.maxwell.syr.edu!wn4feed!worldnet.att.net!135.173.83.225!attworldnet!newsadm From: Jerry <"[email protected]"@worldnet.att.net> Newsgroups: alt.guitar.amps Subject: Re: Blackface vs. Silverface Date: 4 Sep 1998 11:42:15 GMT Organization: S.O.K. '66 Lines: 25 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: 12.79.160.160 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0C-WorldNet (Win95; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:125034 profrets wrote: > > And...... I have only had ONE customer EVER not like the BF thing, he also > liked the caps ON the grids of his '73 Super. He was my worst nightmare > customer that turned into my most loyal customer by virtue of making his amp > reliable, even though it sounded obnoxious. > [email protected] I was playing professionally and working in music instrument sales back when CBS/Fender began to change the specs on the amps. Between 68 and 72 musicians began to notice the difference and demand grew for the old ones. In general terms, the new amps had more clean headroom, lost crispness and sparke and required were far too much gain to get them to distort, if they would at all in the classic sense. My stores amp technician at the time started comparing the schematics and experimented with a few SF's, switching them back to the old specs (we weren't sure t here weren't other componentry changes, so there was no guarantee it was just the resistor values & caps, etc.) It became clear then that we could fairly easily make them sound like the old ones and we began getting lots of requests to do these mods, this as early as about '71. Now, the worst part was the response from CBS/Fender. When we met with them and pointed out the complaints we were received from players about the amps, they basically just told us we were wrong! Ed Jahns Xformers From [email protected] Thu Jan 8 10:45:32 CST 1998 Article: 79310 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!newspeer.sprintlink.net!news.sprintlink.net!Sprint!worldnet.att.net!newsadm From: Rich Koerner Newsgroups: alt.guitar.amps Subject: Re: Replacing 6V6 tubes in DR Date: Thu, 08 Jan 1998 03:28:47 -0500 Organization: Time Electronics Lines: 38 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: 12.68.34.201 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.03Gold (Win95; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:79310 If I may add to this a little piece of information,...... > > Lord Valve Speaketh: > This subject was done to death about a year ago, as I recall. You > might want to pull up some dusty DejaNews articles on the subject and > read all about it...but here's the skinny, in a nutshell: Fender power > trannies are designed with a lot of thermal headroom. People tend to > compare the heater current specs for the 6V6 and the 6L6 and start > foaming at the mouth that it's *twice as much* current without stopping > to realize that the power tube heaters only use a portion of the total > heater current...the preamp tubes (and the pilot light, for that > matter) use the rest, and when you add up the TOTAL heater current > demand, you find out that the extra current drawn by a pair of 6L6 > heaters isn't really anywhere near *twice* the amount drawn by the > entire heater string (and the pilot lamp). Since the Fender heater > winding is very conservatively designed, in *realworld* applications > this modest additional current demand has no deleterious effect on the > tranny. When such Fender X-formers are found, remember the name Ed Jahns. He was the man responsible for that conservative design preference which makes this mod possible. In my short relationship with Ed, he was always at odds with the demands from the suits. One place Ed would not compromise was in the x-formers. Ed left his signature in the Fender amps he had a hand in designing. Everyone knowns the sound, I just thought we all should know the name that goes with it is Ed Jahns. Regards, Rich Koerner, Time Electronics. http://home.att.net/~rich-karl/ Eyelet Board Problems From [email protected] Mon Apr 21 22:23:33 CDT 1997 Article: 46470 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!newspeer.sprintlink.net!news.sprintlink.net!sprint!howland.erols.net!ais.net!news.idt.net!nntp.farm.idt.net!news From: [email protected] (Karl LaFong) Newsgroups: alt.guitar.amps Subject: Re: Another DR Noise Problem Date: Tue, 22 Apr 1997 04:37:24 GMT Organization: IDT Lines: 23 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: ppp-33.ts-6.chi.idt.net X-Newsreader: Forte Free Agent 1.0.82 Xref: geraldo.cc.utexas.edu alt.guitar.amps:46470 [email protected] (Siege7) wrote: >I have a '65 DR and am having similar frustrations. The noise eminating >from the amp is a bit different in that it is a "ticking" type noise that >only appears while playing the guitar thru it. (sustain a chord and you >hear an accompanying ticking noise). Fender style fibre eyelet boards are very prone to a variety of odd little paranormal pheonenoms, ticking being the most common. The board itself is made of vulcanized cardboard basically, and can soak up ambient moisture if it's humid enough. This makes the boards very lively electrically. I've measured micro voltages where there shouldn't be when they display the dreaded tick. Fender attempted to address this problem by waxing the boards, which worked, but also made the entire inside of the amp prone to getting fouled up with wax once the amp heated up and the wax vaporized. I've seen gunked up pots and tube sockets alot on the wax dipped boards. My suggestion is to take a hair drier to the board. Warm setting, low blow for about 4 or five hours. Longer if it persists. Keep amp away from high humidity if possible. It's a crazy low tech solution, but tube amps are crazy low tech items... LaFong Faceplate Restoration From [email protected] Sat May 24 14:46:29 CDT 1997 Article: 50808 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!cliffs.rs.itd.umich.edu!newsxfer3.itd.umich.edu!portc01.blue.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Info Needed On Restoring Fender Amps Date: 24 May 1997 17:51:29 GMT Lines: 11 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: Xref: geraldo.cc.utexas.edu alt.guitar.amps:50808 YES! Rodgers Amps down in Florida restores and remanufacturers faceplates. His prices are HIGH, but he does good work. Give old Larry a call at 941-594-5875. Mind you, he does NOT sell new repro faceplates to anyone, because Fender's lawyers would sue his ass off. You MUST send him an old original faceplate. If he can fix it, he will. If it's too far gone, than and only then can he make a new one, and he MUST keep your old damaged one. You can thank Fender and their lawyers for all those requirements. Factory Mistakes From [email protected] Thu Oct 24 10:10:06 CDT 1996 Article: 25596 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newspeer.gsl.net!news.gsl.net!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: Fender Bandmaster Date: 24 Oct 1996 05:49:20 GMT Organization: Netcom Lines: 17 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: den-co10-06.ix.netcom.com X-NETCOM-Date: Thu Oct 24 12:49:20 AM CDT 1996 In <[email protected]> [email protected] (Jack Price) writes: Something I have noticed in all but a few BMR I've worked >on is that the bright switch cap is wired incorrectly right from the >factory. That person on the production line must have had his eyes >closed or something. I always fine it comical when soemone brings >over their BMR and I go right for the switch, and they say, "Yeah it >doesn't do much does it?" I grin. That's not the only one...most of the silver-face master vol amps have the shield on one of the cables to the master vol pot connected to the wrong side of the horizontal 100-ohm resistor. Move it to the other side. Fat Willie [email protected] (Lord Valve) Fender 6V6 Overvoltage From [email protected] Fri Aug 5 09:54:07 CDT 1994 Article: 25250 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!europa.eng.gtefsd.com!newsxfer.itd.umich.edu!uunet!newstf01.cr1.aol.com!search01.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: rec.music.makers.guitar Subject: Re: Best source for 6v6 tubes? Date: 5 Aug 1994 02:39:05 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 30 Sender: [email protected] Message-ID: <[email protected]> References: NNTP-Posting-Host: search01.news.aol.com In general, the Russian "Sovtek" brand tubes are decent. As I'm sure you know, those Fender amps ran the 6V6s at a plate voltage of 420 -425 volts. The maximum rating on a 6V6 is 360 volts. They got away with overvoltaging them because the tubes they used were great. Nothing compares with the old American tubes. This was a particularly sensitive point when you really cranked it up and the tube was driven to saturation. In this mode, the peak plate voltage on the tube is double the normal DC voltage, which in this example would be about 840 volts. Now pick up two 6V6s, one American, the other Russian, and look inside at the guts. You'll notice that the American tube has larger diameter grid support rods and the element spacing is slightly greater. The Russian 6V6 sounds fine although some can be fairly microphonic (I had one in my reissue reverb that I had to throw out). The American tube is simply constructed more ruggedly and it can tolerate more abuse. I simply don't believe that the Sovtek would be reliable when exposed to such an overvoltage condition and in the high vibration environment of an amp. I've spoken with other repair guys who claim they short out when put in a Fender and the amp is run full tilt. American 6V6s can still be found for about $15 each, they're well worth it. You really can't compare the life span of a 6V6 in a Fender to a 6L6 or EL-34 used in other amps, it's like "apples and oranges". Too many variables such as whose 6L6 or EL-34, bias settings, voltages, etc..... Regards. Fender AA568 circuit From [email protected] Thu Jul 27 11:59:04 CDT 1995 Article: 2512 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: cathode-plus-fixed bias Date: 26 Jul 1995 19:12:33 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 13 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com Mark, you're right, I don't care for the AA568 circuit, it just sounds weak. I have personally listened to a 68 Super Reverb, before and after, since I did the electronic conversion. I can say in all honesty that once that combination bias crap was removed and the amp put back to fixed bias only, and a 5AR4 rectifier, it was louder and punchier sounding. The guy who owns the amp agreed with me as well on this. Another item that has a major impact on the sound of the amp is the speakers. If you want to compare the sound of two chassis, use the same speakers for the test. I'm not impressed with the ceramic magnet speakers in my friend's 68. Regards. From [email protected] Wed Aug 20 12:33:26 CDT 1997 Article: 60740 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!howland.erols.net!infeed1.internetmci.com!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!newstf02.news.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] (Lektrkblus) Newsgroups: alt.guitar.amps Subject: Re: 64 DELUXE Foot Switch Help Date: 19 Aug 1997 21:51:17 GMT Lines: 22 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:60740 >Subject: 64 DELUXE Foot Switch Help >From: [email protected] (Tokaitele) >Date: 19 Aug 1997 19:39:49 GMT >Message-ID: <[email protected]> > >I just bought a 64 Blackface Deluxe. It sounds great but there is no >footswitch for the vibrato channel. If I put in an RCA jack and ground it >the vibrato works fine but this doesn't seem practical. Is there a way to >find a switch that works in radio shack or someplace? I'd appreciate any >help. Please copy me via email if you have good advice. [email protected] > > Carvin sells a dual footswitch for thier amps for about $20.00. This is less than the price of just the two switches. I believe it can be taken apart and modified. I'm going to get one for my Deluxe Reverb II and modifiy it to suit my needs. You can't beat the price, and you may find an ingenious use for the extra switch. Chuck. [email protected] From [email protected] Wed Aug 20 12:33:37 CDT 1997 Article: 60772 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer.sprintlink.net!news.sprintlink.net!Sprint!howland.erols.net!panix!news.panix.com!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps Subject: Re: 64 DELUXE Foot Switch Help Date: 20 Aug 1997 10:22:09 -0400 Organization: Panix Lines: 23 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix3.panix.com X-Newsposter: trn 4.0-test55 (26 Feb 97) Xref: geraldo.cc.utexas.edu alt.guitar.amps:60772 Tokaitele [email protected] wrote: >I just bought a 64 Blackface Deluxe. It sounds great but there is no >footswitch for the vibrato channel. If I put in an RCA jack and ground it >the vibrato works fine but this doesn't seem practical. Is there a way to >find a switch that works in radio shack or someplace? I'd appreciate any >help. Please copy me via email if you have good advice. [email protected] Any Fender dealer can get it for you (Mojo dealers stock 'em too). You'll have to cut off the 1/4" plug and solder in a phono plug. It'll cost around $35. Alternately, Yamaha dealers have a one button footswitch for around $10. It doesn't look like the Fender but if appearance isn't important (and price is) you might prefer it. -Len Moskowitz Core Sound WWW site: http://www.panix.com/~moskowit [email protected] From [email protected] Wed Aug 20 12:33:48 CDT 1997 Article: 60773 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!vixen.cso.uiuc.edu!howland.erols.net!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] (Jomack) Newsgroups: alt.guitar.amps Subject: Re: 64 DELUXE Foot Switch Help Date: 20 Aug 1997 14:52:49 GMT Lines: 19 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:60773 >I just bought a 64 Blackface Deluxe. It sounds great but there is no >footswitch for the vibrato channel. If I put in an RCA jack and ground it >the vibrato works fine but this doesn't seem practical. Is there a way to >find a switch that works in radio shack or someplace? I'd appreciate any >help. Please copy me via email if you have good advice. [email protected] >>Any Fender dealer can get it for you (Mojo dealers stock 'em too).< >>You'll have to cut off the 1/4" plug and solder in a phono plug. It'll< >>cost around $35.<> >>Alternately, Yamaha dealers have a one button footswitch for around $10.< >>It doesn't look like the Fender but if appearance isn't important (and< >>price is) you might prefer it.<< Or, if you are solderifically challenged like myself, you can buy a adaptor plug 1/4" female to RCA male (Hosa and others), and use ANY 1/4" switch - I use an old Boss FS-2 w/ my Super Reverb - nice long cable and wider spaced buttons- important if you are a bigfoot as I am. Back to JT30 Home Fender Amp Covering From [email protected] Sun Oct 9 10:51:12 CDT 1994 Article: 25639 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!scipio.cyberstore.ca!yvr.cyberstore.ca!jnelson From: Jay Nelson Newsgroups: alt.guitar Subject: Re: How old is my amp? Date: Fri, 7 Oct 1994 16:56:58 -0700 Organization: Cyberstore Systems Lines: 55 Message-ID: NNTP-Posting-Host: yvr.cyberstore.ca Mime-Version: 1.0 Content-Type: TEXT/PLAIN; CHARSET=US-ASCII Reply: > Franks Jr S. A. (Stacy) ([email protected]) wrote: > : What color tolex is it covered with... black, brown, blonde? That would help get in > : the ballpark, yearwise. > > What IS the year range for the tolex colors? What about > silverface v. blackface and such? > Roughly: White/Tan Tolex - '61 to'63 Black Tolex - Blackface - '63 to '67 Silverface - '67 to'8? Pseudo Blackface - sometimes in '80's (ie. Twin Reverb II) With the White/Tan tolex, the lighter colors were usually used on the heads. Also, in this era, the color of the grillcloth used changed (ie. tan, oxblood). Finally, there was a distinction made between rough and smooth tolex. In regards to the original question, the company name on the faceplate of blackface amps changed after the Fender takeover by CBS. The name changed from "Fender Electric Company" to "Fender Musical Instruments". The amp would have been a '66 or '67 most likely. If anyone can provide more details for the above, please do. I would be interested in fleshing out the sketchy details I know. Jay N. > > > > > > > > > > > > > > > Fender Amp Dating From Keith_M._Danby%[email protected] Tue Oct 4 22:45:42 CDT 1994 Article: 25387 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!uunet!uunet.ca!uunet.ca!dmog10.bell.ca!news.sygma.net!magic!Keith_M._Danby From: Keith_M._Danby%[email protected] (Keith M. Danby) Reply-To: Keith_M._Danby%[email protected] Newsgroups: alt.guitar Distribution: world Subject: Re: How old is my Guitar amp? Date: 04 Oct 1994 01:57:09 GMT Message-ID: <[email protected]> Organization: Magic Online Services Toronto Inc. Lines: 42 Dating Pre-CBS Fender Amplifiers Fender amps made after 1953 had a date code stamped on the tube chart located on the inside of the cabinet of self-contained amps and inside the amp head on piggy-back models. Sometimes the factory stamped the tube chart code onto the amp chassis too. Look for two small letters in rubber-stamped ink but be sure not to confuse the date code with the production number, the model number, or the serial number. The first letter indicates the year of manufacture, starting with "A" = 1951, through to "O" = 1965. The second letter is the month of manufacture, starting with "A" = January, through to "L" = December. For some odd reason, "G" is not included in the month coding. Example: If your amp has an ink-stamped code of "GD", is would have been manufactured April, 1957 Fender had another date code system for early-60's speakers and amp chassis. If the speaker is a Jensen (most pre-CBS Fenders used either Jenson or Oxford speakers), the code stamped onto the speaker would start with 220 (Jensen's company code) and then followed by a three digit code. The first digit after Jenson's company code indicates the year of manufacture starting 1951. The second two digits indicated the week of manufacture. So a speaker stamped 220122 would indicate it's manufacture of the 22nd week of 1951. If the speaker is an Oxford (Fender used Jenson and Oxford speakers for Pre-CBS amps), Oxford company code was 465 and the last three digits were coded in the same way as the Jensons. One thing to keep in mind is that both companies repeated the same numbering every decade. So you'd have to guess whether the speaker was made in 1951 or 1961. A "2" (manufacture in 1952) could mean the speaker was made in 1952 or 1962. Fender also used another code system for early-60's speakers amp chassis too. You may see something like "AB 0763" on a speaker. It's easy to see that this would be the 7th week of 1963. Speakers are more confusing to date than the amps. Also, the speaker date should be earlier than the amp date. If not, that tells you that the speaker may not be the original. Fender Amp Tremolos From [email protected] Mon Nov 20 13:18:03 CST 1995 Article: 5593 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!newsspool.doit.wisc.edu!decwrl!brighton.openmarket.com!uunet!in2.uu.net!prodigy.com!usenet From: [email protected] (Joseph Pampel) Newsgroups: alt.guitar.amps Subject: Re: Vibrato retrofit Date: 20 Nov 1995 07:03:02 GMT Organization: Prodigy Services Company 1-800-PRODIGY Lines: 73 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: inugap4.news.prodigy.com X-Newsreader: Version 1.2 [email protected] (Mark Garvin) wrote: > >In <[email protected]> [email protected] (Dr Distortion) writes: > >>Mark Garvin ([email protected]) wrote: >>: With a little ingenuity, the LDR version could be made to do this >>: as well. If I were retrofitting an existing chassis, I'd personally >>: use a solid-state oscillator and an LED rather than chop holes for >>: tubes and use a click-prone neon. The Vibrochamp just uses a single triode osc to modulate the bias on a pre-amp stage. Safe, and neat sounding. :-) It's the Vibroverb (and some others..) that modulated the bias on the outputs, which I think sounds great, but is a potentially dangerous retrofit I suppose. >>I'm glad to hear I'm not the only person who feels this way. I'm all for >>all-tube signal paths, but I do have to laugh when I see the guitar amp >>ads touting "all-tube tremolo." Solid-state oscillators work just as well.. > >Yeah...why go thru all that just to light a little bulb? >And neon bulbs come with a whole set of their own problems. Just for the record I've had really good luck re-building the osc circuits in BF amps with new high temp poly caps (the smallest I can get in 600V, Mouser has some good ones) running the leads exactly as the layout diag calls for and keeping all leads on caps etc. short. No more clicks, and a better waveform avait ye who wouldst try this. Almost guaranteed. >Now that we're on the subject of tremolos, why did Fender use a >50k pot? Why not a 100k or even higher? Due to the reverse-log >taper, it's not as if 1/2 of the range would be wasted. To optomize gain into the power amp stage? The amps get dirty in a hurry without that 50K pot.. that's for sure. >>Fender used in the brown-Tolex amps (such as the Concert, Super, etc.). >>This is the type that sends the guitar signal through a simple passive >>crossover and trems the highs and lows separately, imposing the trem > >Yeah, they had some strange name for this (I forget). Pretty >archaic-but-clever design. My brother has an old Showman with >this type of tremolo. Nice long row of 12ax7's in that thing. They called it "Harmonic Trem" In addition to tremming the highs and lows seperately, they combine them out of phase so you have a phasing effect that responds to your pick attack. Sounds neat enough that a lot of folks think it is FM mod, but it isn't. VOX seems to have snagged the idea & most of the circuit for the AC30, but then made it non adjustable for some inexplicable reason.. Really complicated circuit just to get some trem going, and also a somewhat tempermental one. Very sensitive to B+ changes, individual tubes, phase of the moon. Fun to play with, that's for sure. I've been working with it for some time now, since restoring a '61 Concert for a friend and falling for the sound. I've been finding out how much depth you can achieve before the mixer circuit "craps out" and amazingly enough you can get a halfway convincing Leslie sound out of one of these circuits with some tweaking. No kidding. Only drawback to the circuit is a low mid cut that is an artifact from the hi-low network.. although since most guitar amps build in a low-mid cut, it's not that big a deal. Anyway I've been busy down in the dungeon with an old SF twin chassis that I'm building into my next franken-amp.. A '61 Concert pre-amp with the "harmonic" trem circuit and a cathode biased 6L6 output stage for maybe 40W? That should do me for a while.. :-) Joe Fender BF Bassman mods From [email protected] Thu Mar 2 11:57:42 CST 1995 Article: 42213 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!math.ohio-state.edu!magnus.acs.ohiostate.edu!csn!boulder!abbot.Colorado.EDU!not-for-mail From: [email protected] (John Mastrangelo) Newsgroups: rec.music.makers.guitar,alt.guitar Subject: Re: BF Bassman mods? Date: 2 Mar 1995 09:59:12 -0700 Organization: University of Colorado, Boulder Lines: 146 Distribution: world Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: abbot.colorado.edu Xref: geraldo.cc.utexas.edu rec.music.makers.guitar:42213 alt.guitar:37395 In article <[email protected]> [email protected] (David Covell - MPG DA) writes: > Preface: I own a '68 Bassman (AB165) which I like to use as a project amp so I am speaking directly from experience. >I picked up a mid-'66 Bassman last weekend; it's an AB165 circuit and sounds >really great as it is (stock). However, I'm still interested in mods for it to >get a bit more gain at lower volumes without sacrificing the clean tone. More gain? Mine breaks up at 3 on both channel with vintage Strat pickups. How much gain do you want? > >I got the Bassman because the extra tube and larger output transformer make it >a promising mod platform for me to experiment and learn on. I see two simple >mods and a more complex one as good candidates: > >1. Put a pot (1M or larger) in series with the 470K resistor in the feedback >loop across the extra gain stage (preceding the splitter) to allow variable >reduction in negative feedback and pick up some more gain into the splitter. >Question here: will that overdrive the splitter, the output, or both? And is >that a good idea? WARNING!!!!!!!! THIS IS A TERRIBLE IDEA!!!!!!!!! It is a very unsafe practice connecting plate voltages to panel mounted controls, especially 99 cent pots. I know of _no_ amp designs that implement any of these ideas. Additionally: Increasing the value of that resistor will have no audible effect. The resistor is there to stablize the gain stage, not to set the gain. In fact, the gain of that stage looks something like this: Gain = mu/( 2 + x/Rf) where mu is the gain of the tube , and "x" is much smaller than Rf (the feedback resistor). (I did this analysis a few months ago and have it documented, although it is not handy, I'll post it tommorrow.....) So you see, the feedback resistor has vitually no effect on gain untill it is reduced to a value less than "x", which is much smaller than Rf ( again, I'll post a value tommorrow). The previous Bassman AA864 circuit uses a 220K/220K voltage >divider into this stage rather than negative feedback. That would indicate a >%50 reduction in signal into that stage, right? Yes, and the .001 cap creates a low-pass filter. (decreases treble) >Can I assume then that the 470K R in the AB165 is performing roughly >the same reduction? Absolutely not. One is a negative feedback circuit. The other is a voltage divider/lowpass filter. > >2. Put a double pot of at least 250K in series with the 220K feedback resistors >from the output plates to before the coupling caps to reduce negative feedback. Yikes! Please don't connect the plates of your power tubes to any panel mounted pots. Don't take this personally, but this is a perfect example of the saying "A little bit of knowledge is a dangerous thing" >Or, should I remove these and configure the feedback loop like the standard 820 >used in most Fenders? It is safe to remove the resistors . These resistors limit the gain of the power stage. Removing them will give you roughly 3dB more gain (depending on what tubes you have). Converting to the "standard feedback circuit" as seen in most Fenders will give you an 18dB boost at 60 Hz. It's like turning your bass control up 10 more numbers. It also _decreases_ gain by 3dB from roughly 1kHz up. I know this for a fact because I performed this mod on _my_ AB165 and documented it with a pink noise generator and spectrum analyzer. > >3. Add a cathode resistor and bypass cap and insert the unused half of the >extra tube either before or after the tone stack. With your current level of understanding, adding a gain stage is way beyond you (not a flame). Can extra stages be added >without the pronounced high-pass effect they seem to have in Boogies? Yes. My main >complaint with Boogies and other cascaded-stage overdrive amps I've heard is >that as soon as the extra stage is switched in the lows are just gone. Is that >intentional to avoid flubbiness at high gains? Yes. I'm looking for subtle gain >enhancement and fatness rather than massive distortion so I want to preserve >the frequency response on the clean tone whan I add more gain. Now you're talkin'. Remove those 2 pesky 220k feedback resistors off the power tube plates. You'll get about 3dB more gain and the bass will "tighten up". Jack Zucker and I both did this mod and we both got similar results and liked it. This may be all you need. If this is not enough, e-mail me and we'll take the next step. > >As is likely obvious from the above naive speculations I'm still on the steep >part of the tube amp learning curve. I'd thus appreciate any advice about how >to optimize the Bassman (or my Showman head) for fat clean tones and subtle >overdrive. That's o.k. We all have to start at the bottom. Tube amps are both very delicate and very dangerous things. Remember, you are playing with fire. On a side issue, several weeks ago you wanted to "warm up" your HiWatt. I gave you a tone stack cap change that will give a you a warmer low end. Did you do it? John Mastrangelo Osprey Amplification Fender BF SF changes From [email protected] Sun Feb 4 17:46:55 CST 1996 Article: 9082 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.eas.asu.edu!news.asu.edu!ppp2-16.INRE.ASU.EDU!PYLOT From: [email protected] (Ruth and Dale VanZile) Newsgroups: alt.guitar.amps Subject: Re: BF conversion for Bassman? Date: Mon, 5 Feb 1996 01:06:32 Organization: Arizona State University Lines: 54 Message-ID: References: <[email protected]> NNTP-Posting-Host: ppp2-16.inre.asu.edu X-Newsreader: Trumpet for Windows [Version 1.0 Rev A] In article <[email protected]> [email protected] (George Kaschner) writes: >A lot of the detailing comes down to not >only component selection but lead dress - how a particular wire gets from >one place to another. Even if you match component values and lead dress, >you may find that the power transformer is giving a higher voltage to the >tubes. Lead dress is the biggest change, and is most likely what necessitated all the extra parasitic oscillation supression (all those 'extra' caps). See, UL decided that they wanted to see a plastic-insulated wire in the amps, for increased safety. This forced a change in lead dress, as the plastic wires tended to melt and short out when run under the tagboard like the older amps' cloth-covered wire was. So, the wires were moved, and then parasitics started showing up due to the lead dress not being as good as the old, original amps. Since they didn't have Leo there any more telling them not to do it, at this time, the engineers decided to add that wierdo cathode resistor and cap to the output tubes, to get rid of all that unwanted distortion. A good idea for hi-fi, a bad idea for guitar. BTW, I've seen Bassman heads with the cloth-coverd wire clear into early '68, SF with aluminuminum trim and all, so you're probably still wired with it... >Before you even start modding the silverface, make sure it is working up >to spec. Before you change anything, look at your tube chart for AB165 or AA864. Then look inside for the cloth-covered wire. If you have both of these, you don't need to change a thing.... Then: >Check the power supply filters, Look for white powdery or globby stuff oozing out of the positive end (usually) of the caps. If they're not oozing, leave 'em alone.... >put in fresh tubes, and properly bias the amp. If the thing needs 'em. Look at the power tubes in front of a white sheet of printer paper, in good light. If you see any brown deposits on the glass (called 'emission burns') and/or a brown ring around the getter flashing (the silvery stuff on the inside of the tube's glass envelope), start saving for new tubes. Try the Sovtek 5881/6L6WGC, as they're really solid, and many people (myself included) like the tone. >Then, carefully consider the impact of each >change you make. Don't get caught up in making sweeping changes >throughout the amp at once. If you want to learn how the changes affect >the amp, make one mod at a time and listen to the effect before you >proceed to another. Consider keeping a log of changes made and their >result. That way if it starts sounding ratty ( I almost said "like a >Torres") you can change it back. Good advice... Dutch Fender Bias Pot Failures From [email protected] Wed Mar 20 12:16:57 CST 1996 Article: 7662 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!sgigate.sgi.com!imci3!imci4!newsfeed.internetmci.com!panix!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: rec.audio.tubes Subject: Re: Cherry red hot tube... Date: 19 Mar 1996 19:34:08 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 26 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: panix2.panix.com >[email protected] (Mark Garvin) wrote: >>Good answers from Larry. Just thought I'd mention that I usually >>patch a relatively high resistor (usually around 100k or so) from >>the NEGATIVE end of the bias pot to the center tap. If the pot >>fails, the resistor will pull the grid down to a safe level rather >>than letting it float. Jack Price writes: >I've seen you post this suggestion more then once. This is really good Uh-oh...I'm repeating myself...[Uh-oh...I'm repeating myself...] >advice. Cheap insurance for your output tubes. What I have seen several >times now from just 1 year of a home repair/restoration business, is that >the bias wire from the bias board to the bias pot, specially if it's solid >wire, will break off right at the pot...instant glow. Yes, limited mojo in those solid wires, I think. Best stay with stranded. Another questionable design practice in Fender amps is putting the 1.5k grid-stopper right on the tube socket. They get heated, stressed by wiggling tubes, flamed by burning screen resistors, etc. and they crack. Not always visible and frequently intermittent. That's the failure that I've seen most often. Mark Garvin From [email protected] Wed Mar 20 20:33:51 CST 1996 Article: 7684 of rec.audio.tubes Newsgroups: rec.audio.tubes Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.io.com!imci4!newsfeed.internetmci.com!uwm.edu!fnnews.fnal.gov!gw1.att.com!gw2.att.com!oucsboss!cigna From: [email protected] (Dave Cigna) Subject: Re: Cherry red hot tube... X-Nntp-Posting-Host: helios.phy.ohiou.edu Message-ID: Sender: [email protected] X-Nntp-Posting-Date: Wed Mar 20 11:13:39 1996 Organization: Ohio University Physics and Astronomy References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> Date: Wed, 20 Mar 1996 16:13:40 GMT Lines: 14 In article <[email protected]>, Mark Garvin wrote: > [snip] >stranded. Another questionable design practice in Fender amps is >putting the 1.5k grid-stopper right on the tube socket. They get >heated, stressed by wiggling tubes, flamed by burning screen resistors, >etc. and they crack. Not always visible and frequently intermittent. The heat is a problem, especially for carbon comp resistors. But my understanding is that the grid stoppers need to be as close to the grid pin on the tube as possible -- something about being at the current anti-node of the oscillations. -- Dave Cigna Fender Bias Schemes From [email protected] Fri Jul 12 21:18:34 CDT 1996 Article: 18748 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!newsfeed.internetmci.com!panix!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: Okay, I'm confused now. (Re: biasing) Date: 12 Jul 1996 22:02:00 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 67 Distribution: inet Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com A couple people have asked about my comments on bias pots. Also, the quote levels in this thread have been a bit confusing, so I'll try to clarify my previous post. >>> Mark Garvin ([email protected]) wrote: >>> The pot on many Fenders is not actually bias pot, but a 'hum-balance' >>> control. It controls bias for only one of the output tubes. It's >>> easy to change it so the pot is a true bias control, though. [...] [note that I said *many*, not *all*] > Bill Spencer writes: >I'm not sure you would want to ... see below. >> [email protected] wrote: >> serve a valid purpose... > Bill? > ['inane condesention snipped' ^^^^^^^^^^^^^^^^^^^^^^^^^^ Huh? I thought Hal's questions were fine. >Bill writes: >These Bassmans uses a circuit not seen in other amps. There is negative >feedback around the output tubes from the transformer *primary* to thier >inputs. At the secondary, the power supply ripple is cancelled out, >mostly, by the two tubes being out of phase. At the primary there is >ripple (about 5 volts). I don't remember that the model number of Hal's Bassman was ever stated. I thought he just said it was a silverface. Most Bassman amps have normal feedback loops, though the phase is reversed on some. The Fender vintage (for all models) that is usually regarded as being the overall best-sounding design is the '63. That's the one that most techs are looking at when they do 'blackface mods'. The control in the '63 amps is a true bias control, hooked to both push-pull sides. [Also note that Fender 'corrected' the '63 design, which operated the output tubes outside of tube mfg's 'grid resistance path to gnd' spec] The bias circuit in some Fenders is indeed wired so that both tubes can be controlled, but in opposite direction. Fender often refers to this as 'hum-balance' but it should not be confused with the humbalance trimmer that's sometimes found on the filament center-tap. This circuit cannot correct crossover notch problems in a pair which is matched but happens to run colder than normal. But Fender *did* make lots of amps with one side set with a resistor divider, and the other side adjustable. I'm no amp historian (not as interested in 'when' as in 'what'), but I believe these were made from '65 to '68. I've seen a ton of 'em. I believe all of the enigmatic combined-fixed/cathode-bias amps are wired this way. Again, I've heard Fender refer to that control as a 'hum-balance' rather than bias, and from what I'm told, it was factory-set for lowest hum level. Both control schemes (bias vs balance) have their merits. For real tweakers, separate bias controls for each output tube will cover both goals. However, given the choice of just one, I'd pick the '63-style bias and try to use reasonably well-matched output tubes. Incidentally, I believe the merits of attaining perfect output tube matching in guitar amps are overstated (aside from the hum questions stated above). The usual goal is cancellation of even harmonic distortion in output stages. Why do that? MGarvin Fender Blackface From [email protected] Sun Oct 9 10:58:38 CDT 1994 Article: 25710 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news.sprintlink.net!deathstar.cris.com!deathstar.cris.com!notfor-mail From: [email protected] (Dr.Distortion) Newsgroups: alt.guitar Subject: Re: How old is my amp? Date: 8 Oct 1994 12:42:54 -0400 Organization: Concentric Research Corporation Lines: 22 Message-ID: <[email protected]> NNTP-Posting-Host: deathstar.cris.com Jay Nelson wrote: JN>In regards to the original question, the company name on the faceplate JN>of blackface amps changed after the Fender takeover by CBS. The name JN>changed from "Fender Electric Company" to "Fender Musical Instruments". JN>The amp would have been a '66 or '67 most likely. Correct. Also, I'd like to point out that while the blackfaces made after the CBS takeover say "Musical Instruments" instead of "Electrical Instruments", they are otherwise identical to their pre-CBS counterparts. The dreaded circuit and layout changes of the CBS era were not implemented until the silverface series came out. (The only exception I'm aware of was the AB165 Bassman, which was made in both black- and silverface versions but the circuit of which was almost certainly a product of CBS's warped imagination). Anyway, my point is this: if you're looking for a blackface, don't pass up an amp just because it's not pre-CBS; the circuitry, layout, parts and level of workmanship are the same. --þ OLX 2.1 TD þ /\/\Dr.Distortion/\/\/ * New York * [email protected] Fender Blues Deluxe Settings From [email protected] Thu Jan 11 13:05:59 CST 1996 Article: 7804 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!msunews!news.mtu.edu!newsxfer.itd.umich.edu!news.uoregon.edu!tank.news.pipex.net!pipex!newsfeed.internetmci.com!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (LarrySB) Newsgroups: alt.guitar.amps Subject: Re: Fender Blues De Luxe settings for Fender Bassman '59 Date: 10 Jan 1996 12:59:25 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 36 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (LarrySB) NNTP-Posting-Host: newsbf02.mail.aol.com <<< Hi, as i just bought a Fender Blues De Luxe Amp, which is the only "vintage" amp I could afford, I like to now which settings of the amp will come the closest to a Bassmann 50's combo? >>>> Oh boy, did you ever open a can of worms with this question. First off, it doesn't sound like a 59 Bassman. That's 'cause it isn't one. But, it's similar to a 59 Bassman circuit, and you can get some pretty cool tone out of it. My favorite settings: Guitar input = jack 1 (not 2) Drive = off Bright = on Volume = 4-5 Bass = 5-6 (my hollow ES-135 feedsback with much more) Treble = 9 Presence = 9 Mid = somewhere in the middle to taste Reverb = 4 I like to tilt it back a little on stage too. Ooh, plug a TubeScreamer into it and it will absolutely wail. Most of the distortion boxes I've tried (even the 'metal' ones) sound really sweet through a Blues Deluxe. -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy All opinions strictly reflect the party line Fender Cap Replacements From [email protected] Thu Sep 5 17:43:07 CDT 1996 Article: 14166 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntp.primenet.com!cpk-newshub1.bbnplanet.com!newsfeed.internetmci.com!news.sprintlink.net!newnews.sprintlink.net!itnews.sc.intel.com!chnews!ornews.intel.com!ptdcs5.ra.intel.com!usenet From: Jack Price Newsgroups: rec.audio.tubes Subject: Re: Substituting Cap values in Fender amps ? Date: Thu, 05 Sep 1996 14:08:31 -0700 Organization: Intel Lines: 29 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ptdi127.ra.intel.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.02 (X11; I; AIX 2) loizeaux wrote: > > Since I can't find 70uf @ 350vdc axial caps, what other values would be > acceptable in blackface Fender amps? I can't even find Sprague 80ufs, > and I don't know how high I can go before I start affecting performance. > These caps are wired in parallel and work closest to the rectifier and > handle 450 volts. Thanks for any info. > > Tom Tom, Most of us are replacing the 70uF @350v with Sprague "Atomic Blue" cans at 100uf @350v. Sprague part number is TVA1620. Perfect fit too! E-mail Mojo Tone for a dealer nearest you. jp -By Day: Intel Portland Technology Development Jack A. Price Group: P6CS Phone: (503) 613-8116 FAX: (503) 613-8261 MS: RA1-303 EMAIL: [email protected] By Nite: PriceLe$$ Amp Restoration Specializing in Fender Amp Restoration/Mods and Custom Designs (503) 641-7146 [email protected] Fender Channel Coupling Caps From [email protected] Sat May 11 11:58:07 CDT 1996 Article: 14888 of alt.guitar.amps Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.io.com!insync!uuneo.neosoft.com!imci3!imci4!newsfeed.internetmci.com!howland.reston.ans.net!newse2a.gnn.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: Princeton vs. Princeton Reverb Date: 11 May 1996 02:00:35 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 30 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> X-Newsreader: AOL Offline Reader In article <[email protected]>, [email protected] (Mark Garvin) writes: > >On the other hand, I haven't found stock Deluxes to sound anemic, >so maybe there's something else wrong. There's something to be >said for LESS preamp stages, you know. And the extra gain stage >in the Fender reverb amps is quite lossy. It's got a big 3.3 meg >resistor in series with the signal. > >I don't get religeous about medium value resistors in series with a >signal, but 3.3 megs is huge. The cap that bypasses it alleviates >some of the problem that would normally be experienced (the resistor >and the grid capacitance of the next stage would roll off highs). >But there is no way to accurately compensate for the effect. There >is usually a difference in tone between the two channels due to this. > > I have found another contributing factor in the difference in tone between the two channels is the difference in coupling caps. The Vibrato channel uses a .02uf and the Normal channel uses a .047uf. I switched to a .047 on the Vibrato channel of a SF Super Reverb the other night because the owner said that it lacked the punch of the Normal channel. This alteration gave him the "punch" he was looking for. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. Fender Combo Reverb trick From [email protected] Wed Jul 12 13:42:20 CDT 1995 Article: 2222 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!gatech!news.uoregon.edu!mars.efn.org!usenet From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Beefing-up Reverb Date: 12 Jul 1995 17:25:15 GMT Organization: Oregon Public Networking Lines: 16 Message-ID: <[email protected]> References: NNTP-Posting-Host: dynip54.efn.org X-Newsreader: AIR News 3.X (SPRY, Inc.) > [email protected] (Daniel A. Powers) writes: > > When the reverb on my Deluxe Reverb is set above 4 or so, there is too much > high-end ringing. I am wondering if a cap somewhere in the circuit could be > added to ground some of this out. If so, what value and where should it be > located to achieve that beefy Junior Brown sound. > > > Thanks > Dan Powers One way to get more control of the reverb on a blackface deluxe is to patch the reverb return into the input of the non-reverb channel; this then gives you EQ on the verb. Requires a cord that's RCA femalle on one end and 1/4 inch male on the other. good luck! -jeff Fender Concert Reissue From [email protected] Sun Dec 18 21:18:40 CST 1994 Article: 30551 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!pipex!uunet!newstf01.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar Subject: Re: Fender Tube Amp Help!! Date: 18 Dec 1994 20:56:57 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 39 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) A bit of historical note. The original Fender Concert was produced in the early 60s. It was almost identical to the later Super Reverb amps, except it did not have reverb, and used a solid state rectifier. These were pretty good amps, if you could either live without the reverb or used an external unit. They were discontinued in the 60s. The more modern Concert from the 80s was designed by Paul Rivera. I have one, and I speak from personal experience. The clean tone channel sounds somewhat dead and dull, and the high-gain channel sounds buzzy and muddy. The problem is that the lead dress and component layout in those amps is really shitty, and in order to keep the damn thing from oscillating, they had to connect capacitors from the plate to cathode of several preamp tubes. This kills tone. Secondly, Paul, for some dumb reason, put all the high gain after the tone controls, so the generated distortion is not really equalized. The result is just not happening. They were available in a 1 x 12, a 2 x 10 and a 4 x 10. They are loud as hell. The thing uses 12AX7/7025 tubes everywhere EXCEPT the phase inverter and the reverb pan driver, where a 12AT7 is used. In Fender tradition, the outputs were 6L6GC and it used solid state rectification. I do NOT believe the new version Concert is the same amp. The NEW Concert is the same electrically as the new Super. The 80s Concert was NEVER very popular, so the "popular demand" is questionable. Regarding Groove Tubes, you should read any of the numerous previous posts on this issue. They are definitely NOT worth the money!!! Bullshit!!! The GT 6L6B is actually the Sovtek 5881. The GT 6L6OS "Old Style" is a NOS GE 6L6GC (a REAL 6L6). Forget the Chinese shit, it sounds bad, blows up, puts out lower power (as does the Sovtek), and dosn't last nearly as long. GT prices are through the roof. Since you can buy the SAME damn tubes from Antique for far less money, it only makes sense to save the dough. Antique sells matched pairs (they have both the Rissian 5881s as well as the GEs), and they will guarantee them. Don't waste your money with GT. Don't fall for their marketing hype. Please feel free to email me axs well, since I won't bullshit you, and I have one of the amps. Regards. Fender Concert Tremolo From [email protected] Tue Jan 9 13:17:01 CST 1996 Article: 5052 of rec.audio.tubes Path: geraldo.cc.utexas.edu!ausnews.austin.ibm.com!keen From: [email protected] () Newsgroups: alt.guitar.amps,rec.audio.tubes Subject: Re: Bias-Modulating Tremolo Date: 9 Jan 1996 15:34:13 GMT Organization: IBM Austin Lines: 34 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: keen.austin.ibm.com Originator: [email protected] Xref: geraldo.cc.utexas.edu alt.guitar.amps:7697 rec.audio.tubes:5052 In article <[email protected]>, Mike Rejsa writes: > : I have an old Magnatone which has the most amazing tremolo you'll ever > : hear, it modulates the tone instead of the volume. It almost sounds like > : the pitch changes as well (but that would be impossible with a tube > : circuit wouldn't it?) This is actually a characteristic of all Magnatone > : amps I've ever heard that had tremolo. Do you happen to know how they did > : it? > > The Magnatones do indeed modulate pitch. Its hard. > There is one Fender circuit that does this, but I can't remember offhand > which one - Weber refers to it in his book. > They modulate pitch in the same sense that phase shifters modulate pitch, by varying the phase delay of a signal through a filter section. This produces the same small time delay that phase shifters do. The Magnatones did this with a voltage variable resistor called a "varistor". A varistor's small signal resistance varies with the voltage across it. The Fender that did something similar was the Concert. That amp split the signal into a high and low band, then did out-of-phase tremolo by the bias modulation method one each band separately, and mixed them back together. This approach was intended to give a better cancellation of the LFO signal since it was out of phase in each band and any leakage cancelled when the two bands were added together. The unintended (?) effect was that the phase shift in the band split filters effectively varied when signals in the crossover between the filters were added back together in the mixer. That effect made for true phase/time shift in the crossover band. I've listened to a Concert down in Workhorse Guitars, and the tremolo is GREAT. R.G. Fender Correct Tubes From [email protected] Sat Mar 18 22:05:59 CST 1995 Article: 514 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uunet!newstf01.news.aol.com!newsbf02.news.aol.com!not-formail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Tinny sounding Fender Pro Reverb Date: 18 Mar 1995 18:43:10 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 48 Sender: [email protected] Message-ID: <[email protected]> References: Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com If you want your Fender to sound RIGHT, use the proper types of tubes as stated on the tube chart. I DO NOT recommend substituting a 12AX7 for the 12AT7s in this amp. I don't think Fender "cheated", but rather some previous owner put in the wrong tubes. Other posts have correctly described the functions of the 12AT7s in this amp and I concur. Using a 12AX7 to drive the reverb pan will actually overdrive the damn thing because the 12AX7 has more gain than a 12AT7. The result is shitty sounding reverb. Bad suggestion. Moreover, in Fenders, this tube is subjected to very high plate voltage (typically in excess of 400 volts), and the circuit has the proper cathode bias resistor for a 12AT7. A 12AX7 won't cut it. the other 12AT7 is in the phase inverter. Again, this stage is set-up for maximum linearity and drive for a 12AT7. Subbing a 12AX7 will increase the gain and give more distortion. If you want distortion, sell your Fender and buy a Marshall. There are no "good" 12AT7s being made any longer. Only current production is Chinese. However, there is still a good stock of NOS American 12AT7s around. The industrial equivalent is called 6201, and I prefer these because they're built more solidly. Regarding the differences between 7025 and 12AX7, previous posts had incorrect information. They're basically the same damn tube. In the old days, the differences were the 7025 was a low-noise version, but otherwise identical. In today's market for newly manufactured tubes, there is no difference. They're both considered "commercial", unless a JAN or other military suffix is appended. The best 12AX7 type of tube being made today is the Russian Sovtek. The Chinese stuff sucks. Basically, the Russkies make a 12AX7WB and a 12AX7WXT. There is little difference between the two. According to the hype, the WXT has higher gain. This is not necessarily so, according to the actual comparative testing I've done. They both have about the same gain, within tolerance limits. Both have low noise and low microphonics. Both can be bad right out of the box!! Get more of these than you actually need, so you can have spares in case you get a dud. For output tubes, the supply of excellent American NOS 6L6GCs is just about totally dried-up. The best current production equivalent is the Russian 5881. Be sure to have the amp properly biased when you install new output tubes or it will sound shitty. Also, be sure to buy matched pairs. Groove Tubes are worth it ONLY if you know nothing about working on amps and you need lots of hand-holding. Otherwise, they're way over priced. All they are is just Chinese and Russian tubes that have been well tested to get rid of the duds, and with GT's logo painted on. I NEVER buy GT, or any other high-priced designer-boutique tubes. Regards. Fender Deluxe Power Trans From [email protected] Thu Apr 18 12:08:48 CDT 1996 Article: 8616 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!newse2a.gnn.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: rec.audio.tubes Subject: Re: 6V6 Substitutions? Date: 17 Apr 1996 13:54:42 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 7 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com >>>.and a seperate filiment transformer. The 6L6s require a *lot* more current. Yes, they (6L6s) require more filament current than a 6V6. However, a Deluxe Reverb power transformer has enough beef to handle the additional load. It's been proven repeatedly. No additional transformer required there. Fender Deluxe reissue From [email protected] Wed Nov 16 12:11:26 CST 1994 Article: 32414 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!pipex!uunet!newstf01.news.aol.com!newsbf01.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: rec.music.makers.guitar Subject: Re: Reissue Deluxe reverb same as original? Date: 12 Nov 1994 05:25:03 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 22 Sender: [email protected] Message-ID: <[email protected]> References: NNTP-Posting-Host: newsbf01.news.aol.com Further to the previous post in response to the question, no, the components inside are quite different from those used in 1965. For one, in 65 they wound the transformers with paper insulation, now they use a plastic bobbin. The thinner paper allowed for tighter magnetic coupling in the transformers. This is particularly important in the output transformer. The passive devices such as capacitors are different as well. The speaker is not the same as the original. The originals were made by Oxford, but the reissues by Eminence are of similar design, even though they are supposed to be Jensen replicas. I'm not sure, but I believe these are the same speakers as used in the reissue Twin. Lastly, the tubes supplied in the reissue amp suck. They use Chinese preamp tubes and Russian 6V6s. These tubes are good for landfill and that's about it. With all that said, the amp does not sound too bad, although it's a bit bright. If it were re-tubed with decent NOS tubes, it would probably sound better and be much more reliable. Regards. Fender Ext Spkr Jack From [email protected] Sat Nov 25 00:16:47 CST 1995 Article: 5729 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!usc!howland.reston.ans.net!ix.netcom.com!netnews From: [email protected] (Randall Aiken ) Newsgroups: alt.guitar.amps Subject: Re: Fender Vib.Rev./Super Reverb / Ext Speaker?? Date: 24 Nov 1995 05:04:21 GMT Organization: Netcom Lines: 89 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: atl-ga10-24.ix.netcom.com X-NETCOM-Date: Thu Nov 23 9:04:21 PM PST 1995 >In article , [email protected] says... > >>I have a Blackface Super Reverb (64-65) and a Blackface Vibrolux >Reverb (64-65). Both of these amplifiers have extension speaker >jacks. I have a Laney 4x12 speaker cab (16 ohms). I was wondering if >I will hurt my amplifiers buy using this speaker cab. with them. >>And... does anyone know what Fender recommended for extension cab >impedance >>for each one of these amplifiers. >> >>Thanks >>Rick Super Reverb amps had 2-ohm output transformers to accomodate the four 8-ohm speakers wired in parallel. The recommended total impedance is 2 ohms, which doesn't let you plug any extension speaker in without mismatching the recommended load. Vibrolux Reverb amps had 4-ohm output transformers to accomodate the two 8-ohm speakers wired in parallel. Here, the recommended total impedance is 4 ohms, again leaving no allowance for extension speakers. One word of warning: Be very careful about using the extension speaker jack. Impedance mismatches can damage your amp. Also, Fender amps use shorting jacks on the main speaker output. This means that if you plug a cabinet into the extension jack with nothing in the main jack the output transformer will be shorted. While this is better than no load connected (or a sharp stick in the eye), it may trick you into turning the volume up all the way and driving the amp hard into a short - not good. I have also seen these shorting jacks get "sprung", where the shorting contact gets bent and the output is left open when you unplug the speakers. If you only use one jack, be sure to use the main speaker out. Now, to your question about the Laney 4x12 cabinet: You have several choices here. First the Super Reverb: There is no good way to use this cabinet as an extension with your Super Reverb's internal speakers and properly match impedances. There are two possible ways that will cause only a small impedance mismatch: One is two just plug it directly in to the extension jack, which would give you a total load of 2 ohms in parallel with 16 ohms, which is about 1.8 ohms. The other would be to rewire the Laney as a 4-ohm cabinet (all 4 speakers in parallel, assuming each speaker is a 16 ohm speaker) and rewire your Super Reverb speakers for an 8-ohm load (two speakers in series in parallel with the other two speakers in series). This would give you a total impedance of 8 ohms in parallel with 4 ohms, which equals 2.7 ohms. I doubt that these small impedance mismatches will harm your amp, in fact, in his book "A Desktop Reference of Hip Vintage Guitar Amps", Gerald Weber claims Fender amps are very tolerant to impedance mismatches as long as they aren't more than 100% off! He's probably seen a hell of a lot more Fender amps than I have, so..... In either case, the cabinets will not be equal volumes due to the impedance difference as well as the speaker efficiency differences. In the case of the second method, you would have to always run both cabinets to maintain the proper load. You could not just unplug the extension and use the Super by itself for practice or smaller clubs. A better approach would be to leave the Super Reverb speaker wiring alone, and use TWO external 4x12 cabinets, each wired for 4 ohms. Unplug the Super's speakers and plug one 4x12 cabinet into the main jack and the other into the extension jack. This will give you the desired 2-ohm load, and allow you to unplug both and plug the internal speakers back in if desired. (Not to mention the added benefit of two very cool-looking 4x12 cabinets on stage with you! :) Next the Vibrolux Reverb: Same problem, different impedances. Here if you plug the Laney into the extension speaker jack you will be loading the amp with 4 ohms in parallel with 16 ohms, which is 3.2 ohms. Although this may not be too hard on the amp, again there will be a large volume difference between the internal speakers and the external cabinet. Since the Vibrolux wants to see a 4 ohm load, you could rewire the Laney as mentioned above for a 4 ohm load and unplug the internal speakers and use just the Laney cabinet. Remember to plug it only into the main speaker jack, and be sure to plug the internal speakers back in when you unplug the Laney, in case you forget and turn the amp on with no speakers connected (don't laugh - it happens!). I hope this helps you. Sure would have been nice if Fender had provided an impedance selector like the one on back of a Marshall....! Randy [email protected] Fender Grill Cloth From [email protected] Tue Oct 4 12:56:09 CDT 1994 Article: 29242 of rec.music.makers.guitar Newsgroups: rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!sdd.hp.com!hp-pcd!hpcvsnz!gwatts From: [email protected] (gary watts) Subject: Re: Source for Fender grillcloth? Sender: [email protected] (News ) Message-ID: Date: Tue, 20 Sep 1994 15:04:27 GMT References: <[email protected]> Organization: Hewlett-Packard X-Newsreader: TIN [version 1.1 PL9.4] Lines: 15 [email protected] wrote: : In article <[email protected]> [email protected] writes: : >I need a source for grillcloth for a '64 Fender Tremolux. It's the : brown/beige : >stuff with the gold metallic flecks. :> : Try Magic Parts 800-451-1922 Also try Fenton Music Group as they have a lot of covering materials as well. Gary Watts Fender ID circuits From [email protected] Tue Oct 24 11:34:44 CDT 1995 Article: 4634 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newsfeed.internetmci.com!uunet!in2.uu.net!panix!notfor-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: BASSMAN INFO? Date: 24 Oct 1995 04:39:21 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 46 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: panix2.panix.com In <[email protected]> [email protected] (TimTube) writes: >Further research has caused me to revise my original post. The AA864 is a >pre CBS circuit. Perhaps some stuck a later chasis in an old cabinet. Or >if you are lucky, Someone put a silver face panel on a blackface chassis. >Once again the transformer dates should shed some light on this. Another >thing would be the wiring. The wiring on the circuit board in an AA864 >would be all cotton, a 1970 amp would have plastic coated wiring. Hi Tim, Never can tell with those things. I've been pleasantly and sometimes unpleasantly surprised. Opened a known '68 silverface Super and found '63 wiring, for instance. Cool, but wierd. I've been thinking about 'non-invasive' tests for various models... '64: I've already suggested a test for the '64. The '64 Bassman has inverted channels, so bridging them should cause cancelations. Still waiting to hear how well this test works. (Please post.) All Bassman circuits after this year have normal phasing, I believe. '65: Measure resistance from pin 8 (cathode) of the output tube socket to ground...this will measure 0 ohms in a '65 and some later models. The '65 should measure close to 182k from pin 1 to pin 6 of the phase splitter (12at7) socket, which is right next to the power tubes. '68: will measure 150 ohms to ground from the power tube socket pin 8. '71: will measure 0 ohms on pin 8 (again), but now will measure only 100k or so from pin 1 to pin 6 of the phase splitter tube. Needless to say, power down the amp before measuring this stuff, PLEASE. In fact, unplug it and wait a couple minutes. You'll have to pull a couple tubes to measure from the tube sockets, but aside from that, you shouldn't have to open the chassis at all. Resistance measurements on phase splitter socket pins may take a second to 'settle in', so hold the probes on there. If you need to check amp vintage on a regular basis, why not wire up a 'dummy' tube base so you don't have to poke wires into sockets. Similar tests will apply to other amps, on a model-by-model basis. Regards, Mark Garvin Fender Input Jacks From [email protected] Tue Mar 26 14:36:04 CST 1996 Article: 11977 of alt.guitar.amps Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.io.com!news.fc.net!news.cais.net!news.ac.net!imci4!newsfeed.internetmci.com!in2.uu.net!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (LarrySB) Newsgroups: alt.guitar.amps Subject: Re: Cool Fender Amp Questions Date: 26 Mar 1996 12:03:18 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 29 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (LarrySB) NNTP-Posting-Host: newsbf02.mail.aol.com Oh, earlier in the thread I stated that the number 1 and 2 inputs are identical on the Deluxe Reverb. I was incorrect. For each the normal and vibrato channels: Input 1 when used by itself, presents a load of about 1 megohm. This is normally what a guitar pickup expects. Input 2 when used by itself, presents a load of about 136 Kohms. This is a much lower impedance than most passive pickups expect. The signal will be attenuated and will have less than normal bandwidth. This low impedance sometime works better with active electronics in the instrument, or with some external effects devices. When inputs 1 and 2 are used at the same time, each presents a normal 1 megohm load. The inputs are isolated from one another by two 68K resistors. The Deluxe Reverb has one more inverting stage of gain in the Vibrato channel. This precludes the use of a jumper to chain the two input channels together. (The signals will tend to cancel because of the phase inversion) Cheers, -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy All opinions strictly reflect the party line Fender Midrange Knob From geraldo.cc.utexas.edu!cs.utexas.edu!zaphod.mps.ohiostate.edu!malgudi.oar.net!sun!vax.cns.muskingum.edu!kimple Mon Mar 8 13:33:58 CST 1993 Article: 2053 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!zaphod.mps.ohiostate.edu!malgudi.oar.net!sun!vax.cns.muskingum.edu!kimple From: [email protected] Newsgroups: rec.music.makers.guitar Subject: Re: MOD: Midrange control for Fenders, BEG LEVEL Message-ID: <[email protected]> Date: 8 Mar 93 11:15:31 -0500 References: <[email protected]> Organization: Muskingum College Lines: 17 In article <[email protected]>, [email protected] writes: > Here's an easy one: adding a midrange control to Fender amps that have no > midrange control. (Tube amps) > > On the left hand tab of the Bass control (looking at it from the back) is a > 6.8k resistor. This is Fender's 'fixed' midrange. Replace it with a 10Kohm > potentiometer, and that's it! If you want a 'boosted' midrange, you may want to > try a 25Kohm pot. Well...I've been a bit vague here...that's what I get for doing this while sick...but anyways... The resistor goes from the left hand tab of the pot to ground. when replacing this, run a wire from the left hand tab of the bass pot, to the middle tab of the midrange pot. The left hand tab of the midrange pot should then be wired to ground. jd Fender Normal Channel From [email protected] Mon May 27 13:54:41 CDT 1996 Article: 10192 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newsfeed.internetmci.com!in2.uu.net!winternet.com!n1ott.istar!n3ott.istar!ott.istar!istar.net!newsjunkie.ans.net!newsfeeds.ans.net!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender Normal Channel Date: 26 May 1996 13:39:05 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 37 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com Xref: geraldo.cc.utexas.edu rec.audio.tubes:10192 alt.guitar.amps:15851 You should have known better about Torres, warnings have been posted in this group several times. With that said, I can recommend something similar to Torres, but I suspect you'll like the tone better. Go back to the 220k plate load resistors and the 2.2k cathode bias resistors. EXCEPT, use the normal size cathode bypass caps (25 uf) instead of that .68 bullshit. Put the 56k resistor back in the tone stack. Replace the treble cap with a 330 pf. Replace the .1 uf bass cap with the old .047 uf cap that WAS the stock midrange cap. Put back in one of the .022 caps into the midrange slot. Now, replace the 10k midrange pot with a 25k pot. I guarantee this won't be overly bright or thin. It should have decent bass and thicker mids than the stock configuration. Gain will be a tad higher, but not tremendously. Be sure to use a fairly high gain 12AX7. If you really want to get trick, drive the tone stack with a FET source follower. Use one of those IR Hexfets, hook the gate directly to the plate of the first preamp tube, hook the drain to the B+ supply and connect the tone stack to the source lead. Also hook a 100k resistor from the source to ground. I would probably use a FET in a TO-220 package, and one rated for 600 volts or higher. Since it will be operating in the linear small signal region, the current rating isn't important, just about anything will work. Ditto for on resistance, a couple ohms is fine. Since there is no voltage gain in the FET follower, it shouldn't color the sound. By removing the loading of the tone stack from the first preamp stage (by using the follower), the gain of that stage should increase considerably. Mind you, all this still won't make the Twin into a death and thrash metal machine, or make it sound like a Marshall or Bogner (thank God). IMO, the reason the normal channel sounds "dull" is the lack of reverb. BTW, have you done a blackface mod on the phase inverter and output stage yet? Regards. From [email protected] Mon May 27 13:55:07 CDT 1996 Article: 10191 of rec.audio.tubes Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.eden.com!matrix.eden.com!keen From: [email protected] (R.G. Keen) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender Normal Channel Followup-To: rec.audio.tubes,alt.guitar.amps Date: 26 May 1996 17:44:59 GMT Organization: Adhesive Media, Inc. Lines: 17 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: matrix.t10.nfs.eden.com X-Newsreader: TIN [version 1.2 PL2] Xref: geraldo.cc.utexas.edu rec.audio.tubes:10191 alt.guitar.amps:15850 Jack A. Zucker ([email protected]) wrote: : I'm looking for a way to "hop-up" the normal channel in my : (non master) Fender Twin without adversely effecting the vibrato : channel. ... : I seem to remember either Mark or R.G. talking about a simple FET : which can boost the gain and maybe with only 2 gain stages to play : around with, the normal channel would be a good place to put that. : Any of you guys remember talking about this ? Keen here. I used an IRF820 Power MOSFET as a source follower to drive tone controls. If your amp has one section of a 12AX7 used as a cathode follower, you can use the mosfet and free up the 12AX7 section for another gain stage. If you just like the sound of a follower-driven tone stack, it works well for that, too, but doesn't give you any more gain. R.G. From [email protected] Mon May 27 13:56:32 CDT 1996 Article: 10199 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!chi-news.cic.net!newsfeed.internetmci.com!panix!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender Normal Channel Date: 26 May 1996 15:49:44 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 90 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com Xref: geraldo.cc.utexas.edu rec.audio.tubes:10199 alt.guitar.amps:15859 In <[email protected]> "Jack A. Zucker" writes: >I tried Torres's mods for "Heating up that normal channel" >last night. Unfortunately, it sounded like shit. >Bright, thin, (It reminded me of Ned Beatty in Deliverence) >1) Seperating the shared cathode in the 2nd gain stage. (Formerly >shared with the Vibrato channel's cathode) Probably not audible, but I have no problem with this change. >2) Converting the cathodes of the first 2 gain stages from > 1500ohm/25uf to 2.2k/.68uf. That's going the wrong direction. You'll get just a bit more gain by going with a slightly LOWER cathode bias resistor, but at the expense of headroom: the plate voltage will be thrown off-center. That 100k plate/1.5k cathode circuit is by classic RCA formula. If you do change the cathode resistor, consider leaving the 2nd stage at the stock 1.5k value. Note that this comment relates to use of 100k plate resistors. The .68uf may be the culprit. Leave the 25u/25v cap. >3) Changing the plate resistors to 220k >4) Changing the tone stack slope resistor to 56k This shows Mr T's lack of understanding of plate loading, unfortunately. There is no point in going to higher plate resistors if you AC-load the plate with a 56k 'slope' resistor. You could get just a bit more gain with a 220k plate resistor if there were no additional loading effects. I'd leave the 100k slope resistor if you are going to experiment with higher value plate resistors. If the plate resistors are changed to 220k, then the cathode resistors should be raised as well. Again, this keeps reasonable headroom. >5) Changing the tone stack from 250pf, .047uf, .1uf to >500pf, .022uf, .022uf The .1 to .022 change is miniscule. Rolls of a tiny bit more bass. The .047 to .022 change makes a bit more sense in that it will give you a bit more low mid, at the expense of less Fenderlike mid-scoop. (I thought you *liked* the Fender mid-scoop!) The 250p to 500p change does the equivalent to the top-mids, but this doesn't make as much sense. The latter two changes will give you a much less scooped, more midrangey sound. This may appear as more gain also, due to the slightly lower 'insertion loss'. >I changed back to the dull/lifeless original circuit but I remember >I seem to remember either Mark or R.G. talking about a simple FET >which can boost the gain and maybe with only 2 gain stages to play >around with, the normal channel would be a good place to put that. >Any of you guys remember talking about this ? It was probably RG. I've used FET followers for drivers when I have to, but I am not a big fan of followers. They sound harsh and barky to me when they overload, though many others like them for that same reason. Are you looking for a more Marshal-like sound? Seems that way, as that's where most of these mods are headed. By the way, the 56k slope resistor could work if it's driven by a follower. That's Marshall's usual topology. The 56k will move the circuit further toward the Marshall sound: less separation between control effects...more mids...less insertion loss...kind of phasey sounding mid notch. Check with Dave Cigna. I think he's got a tone control modelling program on his web page. This should help you to visualize the tone differences. I don't remember if it models any of the plateloading effects, though. How about trying out an active preamp at the guitar side? This would drive the guitar cable more effectively, and would afford a lot more gain if you need it. The Torres mods described here will not give you much more gain so much as just allowing more mids thru the tone controls. There's only so much gain to be had with a couple 12ax7 stages. I have absolutely no problem with raising mids, but I design my own circuits for doing that. The Fender tone circuit is not suited to true mid-boost, if that's what you're after. Mark G. From [email protected] Mon May 27 13:57:14 CDT 1996 Article: 10209 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!newsfeed.internetmci.com!newsxfer2.itd.umich.edu!uunet!in2.uu.net!in-news.erinet.com!en.com!usenet From: Dee Zucker Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender Normal Channel Date: Sun, 26 May 1996 21:12:08 -0400 Organization: Exchange Network Services Lines: 20 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: p14-ts7.en.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0 (Win95; I) Xref: geraldo.cc.utexas.edu rec.audio.tubes:10209 alt.guitar.amps:15885 Thanks once again Mark. In terms of what I'm looking for, I've converted the phase inverter and power section to blackface specs, including removing the .002uf caps (all over the place), etc. I'm just looking to get something usable out of the normal channel. The Vibrato channel sounds great for jazz and country and pretty damn good for early 60's rock as well. Unfortunately, the tremelo photo-resistor was bad and I bought a new photo-resistor/neon pair from Mojo but it does not do that great of a job. It seems that perhaps the resistance is not high enough since the sound never goes completely off. I know blackface amps were not the best for tremelo but my Showman sounds much better for example. Maybe someone else makes a Optoisolator closer to the vintage one ? Another thought was to couple the output from the 2nd gain stage of the normal channel back into the reverb section to have 'verb in both channels, and then to slightly revoice the normal channel. -Jaz From [email protected] Mon May 27 13:57:54 CDT 1996 Article: 10211 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news-e2a.gnn.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: rec.audio.tubes Subject: Re: Fender Normal Channel Date: 27 May 1996 00:45:19 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 59 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: newsbf02.mail.aol.com X-Newsreader: AOL Offline Reader In article <[email protected]>, "Jack A. Zucker" writes: >I'm looking for a way to "hop-up" the normal channel in my >(non master) Fender Twin without adversely effecting the vibrato >channel. > >I tried Torres's mods for "Heating up that normal channel" >last night. Unfortunately, it sounded like shit. >Bright, thin, (It reminded me of Ned Beatty in Deliverence) > >The mod involved: > >1) Seperating the shared cathode in the 2nd gain stage. (Formerly >shared with the Vibrato channel's cathode) >2) Converting the cathodes of the first 2 gain stages from >1500ohm/25uf to 2.2k/.68uf. >3) Changing the plate resistors to 220k >4) Changing the tone stack slope resistor to 56k >5) Changing the tone stack from 250pf, .047uf, .1uf to >500pf, .022uf, .022uf > >I changed back to the dull/lifeless original circuit but I remember > >I seem to remember either Mark or R.G. talking about a simple FET >which can boost the gain and maybe with only 2 gain stages to play >around with, the normal channel would be a good place to put that. > >Any of you guys remember talking about this ? > > Gotta love that Torres, a Marshalll tone stack in a Fender. The problem is that this configuration needs an extra gain stage and the tone stack needs to be driven by the cathode. You could add a tube or a transistor to his mod and it would probably sound OK. Here is an easy no brainer way to "heat up the normal channel", or the other one for that matter. You do lose the bright switch if you want this to be a switchable mod. If you don't want it switchable or just want to try it first, only do step 2. This mod will give a pretty dramatic gain increase. 1. Disconnect all connections to the bright switch. 2. Disconnect the ground connection on the midrange control. 3. Reconnect the midrange control to the bright switch. 4. Connect the other side of the bright switch to ground. With this mod signal normally filtered to ground goes through the amp, no signal is lost at the tone stack. Of course there is no tone control either. If you don't use the bright switch this is a way to get some use out of the switch. If you do use the bright switch, you could add a switch or a push-pull pot for the mod. If you have the bright switch on all the time, you could just wire the bright cap to the volume pot and free up the switch. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. From [email protected] Thu May 30 01:06:58 CDT 1996 Article: 10311 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!chi-news.cic.net!news.nd.edu!spool.mu.edu!howland.reston.ans.net!newsfeed.internetmci.com!in2.uu.net!scnews.sc.intel.com!itnews.sc.intel.com!chnews!ornews.intel.com!ptdcs5.al.intel.com!usenet From: Jack Price Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender Normal Channel Date: 30 May 1996 00:37:50 GMT Organization: Intel Lines: 26 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: ptdi127.ra.intel.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 1.1N (X11; I; AIX 2) X-URL: news:[email protected] Xref: geraldo.cc.utexas.edu rec.audio.tubes:10311 alt.guitar.amps:16091 Dee Zucker wrote: >Another thought was to couple the output from the 2nd gain stage of >the normal channel back into the reverb section to have 'verb in >both channels, and then to slightly revoice the normal channel. Bingo! This is what I would suggest if you want to juice up the normal channel. What I do is couple the norm and vib channel at the reverb input as you suggested, hop up the norm channel just a little by using 120K loads and 820 cathodes. Stick with the 25uf, it's a Fender remember. Oh, don't forget to separate the shared cathode. Which I guess you did at one time? Now that both channels are in phase and the normal is a little hotter, I use a Morely AorB/AandB box to externally channel switch. Usually I play thru the vib channel and then add, not switch, the norm channel. Playing thru both channels, now in phase, produces some really fat tone. But it's still sounds like a Fender. Just fatter! jp -Intel Portland Technology Development Jack A. Price Group: P6CS Phone: (503) 613-8116 FAX: (503) 613-8261 MS: RA1-303 EMAIL: [email protected] Fender RI Reverb Tube From [email protected] Fri Sep 6 10:34:30 CDT 1996 Article: 22142 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntp.primenet.com!uunet!in1.uu.net!nntp.teleport.com!usenet From: "Zack aka vibroman" Newsgroups: alt.guitar.amps Subject: Re: Reverb Units Date: 6 Sep 1996 05:41:39 GMT Organization: Zack Engineering Lines: 20 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: ip-pdx12-25.teleport.com X-Newsreader: Microsoft Internet News 4.70.1155 Dr Distortion wrote: > > Interestingly, I measured the primary impedance of the reverb driver > transformer in this unit at about 13kOhms. This is a bit high for a > 6V6GT (as supplied by Fender with the unit), but just about right for > a 6K6GT. It's almost as if Fender anticipated their customers replacing > the driver tube with a 6K6. (Or else they simply slavishly copied the > original unit, then some bean counter made a last-minute decision to use > the 6V6GT instead since it's cheaper and easier to get). You sir are correct. I call my friend at Fender and that exactly the way it came down. -//////////////////////\\\\\\\\\\\\\\\\\\\\\\\ Zack aka [email protected] http://www.vibroworld.com/~vibroman \\\\\\\\\\\\\\\\\\\\\\/////////////////////// Fender RI Reverb Tweaks From [email protected] Sat Jul 27 15:11:07 CDT 1996 Article: 12530 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!uwm.edu!newsres.gsl.net!news.gsl.net!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: rec.audio.tubes Subject: Re: Fender RI reverb tweaks? Date: 27 Jul 1996 14:07:27 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 29 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com >>>One thing that has me puzzled is that other than the 6V6, isn't the reissue the identical circuit as the original ? If so, why would you want to change component values and why would that make the reverb sound more like an original ? >>>(I admit that having had an original and a reissue, the reissue does not sound nearly as good) Simple Jack. The originals have close to 30 years use on them, so the components have aged and their values shifted a bit. You seem to be an avid tweaker and modifier, this seems like it would be right up your alley. I spoke in depth with Terry Buddingh who wrote the article in GP mag expalining his proposed tweak. He proposes changing the 250 pf coupling cap to a 390 pf. This does improve the sound, since it lets more reverb signal through, particularly at lower frequencies. I have a reissue, and I have taken the process a bit further than Terry. Instead of 390 pf, I used 470 pf, which gives an even bigger sound. Additionally, I loaded down the reverb pan return by soldering a 47k resistor directly across the socket where the return signal plugs in. This further improved fidelity and "bigness" of sound. Lastly, I incorporated a bit of Ampeg engineering. Refer to the schematic for an old Reverberocket. Notice Ampeg put a low pass filter consisting of a 10k resistor and a cap between the recovery tube's grid and cathode. Put that in the Fender reissue and it gets rid of some of the brittleness the reissues have. End result is a Fender reissue reverb that sounds significantly better than stock, IMO. Regards. Fender RI Reverb mods From [email protected] Sat Aug 31 09:47:16 CDT 1996 Article: 21828 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.erols.net!nntp04.primenet.com!nntp.primenet.com!newspump.sol.net!uwm.edu!news.cse.psu.edu!news.ecn.bgu.edu!vixen.cso.uiuc.edu!newsfeed.internetmci.com!newsxfer2.itd.umich.edu!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (LarrySB) Newsgroups: alt.guitar.amps Subject: Re: Reverb Units Date: 31 Aug 1996 02:40:19 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 32 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (LarrySB) NNTP-Posting-Host: newsbf02.mail.aol.com <<<<<< I'm going to buy a stand-alone reverb unit soon, and was wondering if anyone has any experience with any types. I played through one of the Fender ('63?) Reissue Reverb tube units, >>>>>> I just reworked a couple of these. Out of the box they are OK, and a fairly decent imitation of the original. But, the tubes are cheapies and the overall sound isn't quite what a real one sounds like. Fortunately, you can swap out the tubes with NOS 12AT7, 12AX7 and 6K6GT. That will make a huge difference in sound. You can also change the 250pf cap on the volume board to 390pf or 470pf to open up the sound a bit more and make it less brittle sounding. The tubes will cost you about $25-$30. The cap is cheap, but you have to open it up to solder in a new one. -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy All opinions strictly reflect the party line. Read the Blue Glow in Tubes FAQ at http://www.persci.com/~larrysb ****************************** Please, no unsolicited e-mail. Use of this Usenet article to generate email address lists for unsolicited advertisements, constitutes an agreement by the list gatherer and subsequent users of the list to pay the adressee $1000, US funds, per unit of e-mail received. ****Please stop Pegasus Mail!!!**** Lawrence Barras, copyright 1996. All Rights Reserved. Fender Reverb Both Channels From [email protected] Tue Jun 11 21:47:35 CDT 1996 Article: 10729 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!math.ohiostate.edu!jussieu.fr!oleane!hole.news.pipex.net!pipex!tube.news.pipex.net!pipex!lade.news.pipex.net!pipex!news.be.innet.net!INbe.net!news.nl.innet.net!INnl.net!hunter.premier.net!newsfeed.internetmci.com!in2.uu.net!betty.bway.net!news From: Ron Gonzalez Newsgroups: rec.audio.tubes Subject: Re: Fender Normal Channel Date: Tue, 11 Jun 1996 20:03:21 -0400 Organization: Mannes / New School Jazz Program Lines: 61 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: dial08.bway.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0b4 (Win95; I) Jack A. Zucker wrote: > > Ron Gonzalez wrote: >> > > > You're on to somethin' there. I re-wire my Fenders so that the two > > channels are joined (via 220k resistors) right after the output cap of > > the Vibrato channel preamp (.022 mF in most). > > Thanks Ron, > > What about the 220k grid load resistors at the phase invertor. Should those > be lowered to compensate for the loss of gain when adding the 220k resistors > earlier in the circuit ? > > -Jaz ________________________________________________________________________ Jack, Sorry about the confusion... I meant to say that if you have two 220k resistors in a similar config mixing the signals from the two preamp sections *prior* to the reverb circuit, then the two 220k resistors right before the grid blocking cap at pin 2 of the 12AT7 are no longer necessary. The two 220k new resistors should meet right before the point where there is a 10pF cap and a 3.3 Mohm resistor in parallel, but after the .022 and .047 mF caps on the outputs of the two channels. Like this: .022 ----||----- <220k 10pF > |---||---| |-----------| |---------- to pin 7 of 12AX7 mixer < |-^^^^^^-| ----||----- >220k | 3.3M | .047 | | >from outputs (pin 6) =500pF from 470k coming from "Reverb" pot of preamp 12AX7's | | to pins 2,7 of 12AT7 *please excuse my wretched ASCII art* Now you can connect the output cap on pin 6 of the last 12AX7 (.01 mF) to the input blocking cap leading to the input grid on the phase inverter (pin 2 on 12AT7), thus doing away with the 220k resistors that reside there. You can even dipense with the .01mF cap if you like, as long as you retain the .001 mF cap on the input grid of the phase inverter. Your two channels should now both have reverb and be in-phase with eachother to boot! Try plugging an A-B box into the two channels and switching one or the other channel in, or using both at once. They won't cancel eachother out any more. _______________________________________________________________________This is pretty "trick" stuff, and one can seriously screw up a perfectly good amp by mis-wiring it. If you feel I have not explained how to do this adequately, I urge you to show this thread to a good amp tech and have him/her do the mod for you. Have fun, Ron G. Fender Reverb FX loop From [email protected] Mon Jul 1 00:29:42 CDT 1996 Article: 17862 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!newsfeed.internetmci.com!news.sprintlink.net!newnews.sprintlink.net!xroads!ppp.xroads.com!vanzile From: [email protected] (Dale & Ruth VanZile) Newsgroups: alt.guitar.amps Subject: Re: Adding an effects loop to a vintage fender amp Date: Sat, 29 Jun 1996 18:28:49 Organization: Crossroads Communications Lines: 56 Message-ID: References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: slip59.xroads.com X-Newsreader: Trumpet for Windows [Version 1.0 Rev A] In article <[email protected]> [email protected] (telecaster) writes: >From: [email protected] (telecaster) >Subject: Re: Adding an effects loop to a vintage fender amp >Date: 27 Jun 1996 01:40:02 GMT >Dear Trem, > Thanks for speaking out against that Torres fellow. I had a Tremolux >modified by him into a buzzy distortion box that couldn't hold a power tube >bias. I shudder when I see that guy's column in VG, or his advertising. > By the way, I saw your "Vibroclone" mod in 20th Cent. Guitar.. it looks >interesting. Is any Fender (2x6L6 w/reverb) amp through the seventies good >for this project? >-- tele >In article <[email protected]>, [email protected] says... >> >>I do not recommend such a foolish mod to a valuable Vintage pre-CBS amp. >>You'll kill the resale value. If you want an effects loop, buy a new amp. >> Torres is a butcher, beware. He specializes in turning Fenders into >>Frankenstiens. I'm sure you could easily sell the Vibrolux for between >>$900 and $1000, which would finance your new modern amp. Leave the >>vintage Fenders stock. One neat trick you can do that doesn't alter the amp at all is to use the reverb driver as the effects send signal, and return the effects output to the reverb return jacks. Set the effects for 100% wet, and dial in the blend with the reverb knob. Be sure to do two things first, though-1) Make sure that the reverb driver transformer is properly terminated. Build a small box with a pair of pass-through jacks. Set up the reverb send pass-through with an RCA jack (in) and a 1/4" jack (out) and an 8 ohm/10W resistor tied across the signal line (hot to ground) to properly terminate that reverb driver transformer. The return side can be a simple, 1/4" to RCA pass-through to prevent the need for wierd adapter cables of dubious quality from Radio Shack or the like.... 2) If using a line-level (or pseudo line-level) effect unit, start with the output level knob fairly low, and run the amp's reverb knob about halfway up to avoid distortion. Remember, since the reverb tank's signal is /very/ small, the gain stage is set up to reflect that, and it may distort if the effect output is to high.... For the price of a project box, a resistor, and a few jacks, it's a heluva non-intrusive "mod"..... For those of you with Fender Blues Devilles and the like which have SS drivers for the reverb tanks (also all you SS amp guys), you can forget the requirement for loading the reverb driver output. It's only to save the tube-driven driver transformers, which /will short out/ if not properly terminated and dump the preamp B+ to ground through a dead short (no sound) or a high-resistance short (dirty sound at most volumes, weak output--check for lower-than-normal preamp B+). The SS drivers son't seem to have this problem, so enjoy.... Dutch Fender Reverb Reissue From [email protected] Sun Oct 16 09:35:05 CDT 1994 Article: 30158 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!pipex!uunet!newstf01.cr1.aol.com!newsbf01.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: rec.music.makers.guitar Subject: Re: Fender Reissue Tube Reverb Date: 16 Oct 1994 03:23:01 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 21 Sender: [email protected] Message-ID: <[email protected]> References: NNTP-Posting-Host: newsbf01.news.aol.com I have one of the Fender RI Reverbs (mine's a Blonde with Oxblood grille). It sounded real good in the store, so I bought it. When I got it home, I replaced the Russian and Chinese tubes with NOS American and it sounded even better (I replaced the Russian 6V6 with an RCA 6K6, which is true to the original design. 6K6 tubes are no longer in production.). (I also replaced the handle with one of the aftermarket replacements for tweed amps because the stock handle was a bit cheesy.) I have A/B tested it against both original Fenders and the Kendrick. I can say in all honesty, that to me, it sounds every bit as good as an original. Even the guy who owned the 2 originals I used for the test agreed. As for the Kendrick, it's real close. No way is it a "blow away" as was stated in an earlier post. I paid $313 out the door. The Kendricks go for about $550 plus tax. Not worth the extra money, IMHO. I've played gigs with it and the other guitarist used the Kendrick. In a live situation, they sound about identical, I adjusted my knobs like he had his, and the sound was the same. Save your money and get the Fender RI. Regards. Fender Reverb Transformer From [email protected] Mon Mar 13 23:13:44 CST 1995 Article: 458 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!mhv.net!bbs.mhv.net!Distortion From: [email protected] (Dr Distortion) Newsgroups: alt.guitar.amps Subject: Re: reverb transformer Date: 13 Mar 1995 23:27:19 GMT Organization: MHVNet, the Mid Hudson Valley's Internet connection Lines: 29 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: csbh.mhv.net X-Newsreader: TIN [version 1.2 PL2] Mikko Oksa ([email protected]) wrote: : Anybody have data on the 125A20B impedance matching transformer used in : Fender reverb circuits ? What kind of a transformer would I need If I : were to build a silmilar circuit ? I don't have the data handy, but I can tell you how to figure it out. 1) All Fender reverb tanks have an 8-ohm nominal input impedance. So, the secondary winding must be 8 ohm. 2) Are you talking about the transformer that was used with a 12AT7 driver? In that case, the primary impedance of the transformer would probably be chosen to more-or-less match the plate impedance of the tube, which gives you maximum power transfer with a triode. Since both halves of the 12AT7 are being used, the plate resistance is 1/2 that of the stated spec in the tube manuals. So, look up the plate resistance for a 12AT7 at the kind of plate voltage which it sees in the Fender circuit and divide it in half; that will give you the approximate primary Z of the transformer, assuming that they designed the xfmr to match the plate resistance. An even better way is to obtain the actual transformer and take measurements; feed a 1-volt, 1kHz sine wave into the secondary and read the AC voltage appearing across the primary. This will give you the turns (step-up/step-down) ratio. The impedance ratio is the square of the turns ratio. __|__ Dr.Distortion __|__ ----- STAUDCO ----/~~~| New York |~~~\ Fender SF vs BF From [email protected] Mon Dec 4 10:40:28 CST 1995 Article: 3920 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!ix.netcom.com!netnews From: [email protected](Randall Aiken ) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender SR--silverface vs. blackface circuit Date: 4 Dec 1995 00:02:45 GMT Organization: Netcom Lines: 98 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> < <[email protected]> <[email protected]> <[email protected]> <1995Dec1.172547@pomona> <[email protected]> <[email protected]> NNTP-Posting-Host: atl-ga12-21.ix.netcom.com X-NETCOM-Date: Sun Dec 03 4:02:45 PM PST 1995 Xref: geraldo.cc.utexas.edu rec.audio.tubes:3920 alt.guitar.amps:6099 In <[email protected]> [email protected] (Mike Kent) writes: > >I converted an silverface AB568 Super Reverb (mixed cathode/fixed >bias) to the generally more desired blackface AB763 fixed cathode >circuit. Sure, the amp is cleaner and more powerful now, but... I >think I preferred the complex harmonics of the AB568 circuit! > >I have two choices--do a bunch of Weber mods to the AB763 to fatten up >the sound, maybe lose the vibrato and negative feedback, etc.; or, >give the AB568 circuit another try. > >I'd like to hear some opinions about the AB568 circuit, beyond the >tube book lore about how lousy the silverface amps were. Mark Garvin >has said in the past that he suspects the phase inverter circuit as >being a problem, rather than the mixed bias configuration on the >output tubes. Can anyone comment on their experience with >modifications to the AB568 circuit? If the silverface circuit is so >lousy, please explain why. There are so many potential modifications >to try out on any circuit, I'd like to settle on which basic >circuit to work on, rather than waste time going down the 'wrong' >branch of the decision tree. > >[email protected] (Randall Aiken ) wrote: > >>As to a "class A" amplifier sounding better and having "touch >>sensitivity", the reviewers are usually talking about a class AB >>cathode-biased amplifier and calling it a class A amplifier. Due to >>the negative feedback action of the cathode bias resistor and the >>shifting of operating point with signal level, these amplifiers >>generate a richer series of harmonic overtones when driven hard. > >That's what my ears heard when I tried out the AB568 mixed >cathode/fixed bias over the AB763 circuit. Yet everybody avoids AB568 >like the plague. Why? > >--Mike. > I haven't compared the two circuits side by side, so I may be off-base here, but I tend to agree with Mark Garvin. There are a couple of points of interest, though. The AB568 uses separate bias resistors that are bypassed with one capacitor from cathode to cathode. This creates a degenerate feedback arrangement by coupling the two cathode signals together for AC signals, and would be the same (for AC signals) as using a single, unbypassed cathode resistor for both tubes. A far better approach would be to use a separate capacitor for each resistor from cathode to ground, or a common resistor of half the value bypassed with a large capacitor to ground. I don't know why this is never mentioned in the books. In addition, let me clarify my statement about cathode bias shifting of operating point. Cathode bias actually causes a smaller shift in average plate current from zero signal to max signal than fixed bias due to the "self-correcting" action of the degenerative feedback. The voltage drop across the resistor will increase to compensate the additional average plate current drawn by the class AB amplifier. This changes the bias point of the circuit with changing plate current. The average current changes because of the rectification effects of class AB operation on the cathode waveform. Bypassing the cathode resistor prevents degeneration at signal frequencies, but there will be a greater average current due the asymmetry of the rectified cathode waveform. Large transient waveforms will create greater distortion in a cathode biased amplifier. Mark's point about the differences in the phase inverter circuit is a good one. The 47K resistors put the tube on a completely different spot on the plate curves, and lower the gain. In addition, there will be a difference in the balance of the two plate waveforms, since the gain at one side of the phase inverter is larger than the other side, but the plate resistors are of equal value. In addition, there is a rather large 2000pF cap from grid to ground on the output tubes. This will roll of the high frequencies quite a bit, contributing to a difference in tone. They were probably added to prevent oscillations, so be sure to check for this if you remove them. The AB568 circuit has a higher plate voltage; it is probably biased a bit colder than the AB763 circuit to keep the plate dissipation down. This can increase the amount of crossover distortion and change the tone. In conclusion, contrary to what the "experts" with the tube books say, I think Mark was correct when he stated that the phase inverter differences probably contribute more to the tone differences than the 150 ohm resistors. Also, don't believe everything you read; if it sounds better to you with the "bad" circuit, by all means, use it. Also, has anyone tried a direct comparison of the two biasing methods with the same phase inverter circuit and no grid capacitors? Perhaps you could do this, Mike, and get back to us with the results. It seems to me that if cathode bias is universally preferred over fixed bias, a point in between the two would be better than fixed bias alone. Randy Aiken [email protected] From [email protected] Tue Dec 5 15:36:52 CST 1995 Article: 3955 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!newsfeed.internetmci.com!vixen.cso.uiuc.edu!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender SR--silverface vs. blackface circu Date: 5 Dec 1995 03:18:46 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 19 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (TimTube) Xref: geraldo.cc.utexas.edu rec.audio.tubes:3955 alt.guitar.amps:6128 Mike, It has been my experience that the AB763 has throatier low mids with smoother top end than the silverface versions. I would continue with the course you are on but start messing with different output tubes (my favorite in a Super Reverb are the Sylvainia 6L6GC with the single getter) and bias points. Also try a bunch of tubes in the first gain stage, until you find one that you like. Preamp and output tubes vary like crazy. I would definitly keep the 5U4 (not the GZ34 as in the AB763) in that circuit to keep B+ voltage down, also. You can try disconnecting the feedback line. Some guys like this and some don't. This is usually a very dynamic mod, but can also introduce a bunch of noise One last thing would be to put a replace the 100k resistor on the first gain stage plate with a 220k. This will certainly brown it up quicker. Good luck with the tone quest, Tim From [email protected] Tue Dec 5 15:42:27 CST 1995 Article: 6147 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!newsfeed.internetmci.com!in1.uu.net!prodigy.com!usenet From: [email protected] (Joseph Pampel) Newsgroups: alt.guitar.amps Subject: Re: Fender SR--silverface vs. blackface circuit Date: 5 Dec 1995 17:35:54 GMT Organization: Prodigy Services Company 1-800-PRODIGY Lines: 55 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> < <[email protected]> <[email protected]> <[email protected]> <1995dec1.172547@pomona> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: inugap4.news.prodigy.com X-Newsreader: Version 1.2 [email protected](Randall Aiken ) wrote: >resistor for both tubes. A far better approach would be to use a >separate capacitor for each resistor from cathode to ground, or a >common resistor of half the value bypassed with a large capacitor to >ground. I don't know why this is never mentioned in the books. - It's in several of the old "Hi-Fi" design books actually. I'd always wondered about the differences of using seperate Rk's or using 1 Rk of half the value (approx) to bias an output stage. Always assumed the amp makers used 1 resistor to simplify construction, but then tying the cathodes helps to balance the stage also I guess. >Mark's point about the differences in the phase inverter circuit is a >good one. The 47K resistors put the tube on a completely different >spot on the plate curves, and lower the gain. In addition, there will >be a difference in the balance of the two plate waveforms, since the >gain at one side of the phase inverter is larger than the other side, >but the plate resistors are of equal value. I also agree on the Phase Inverter. The amps I've modded allways benefitted from the earlier PI circuit. I think the lower (47K) Rp's were about lowering the output imp of the PI to keep the amp cleaner longer, and also to maximize the Va on the tubes (less resistor, less drop). There are probably a bunch of more complicated reasons but those are the ones I can think of. :-) If you like a lowr gain PI circuit, you acn always use the AB763 type PI but raise the "tail" resistor from 27K up to 47K or whatever suits you. Or if you're a gain hound you can drop it to 6.8K and just go nuts.. >150 ohm resistors. Also, don't believe everything you read; if it >sounds better to you with the "bad" circuit, by all means, use it. I couldn't agree more. All that matters is whether YOU like the way it sounds. >Also, has anyone tried a direct comparison of the two biasing methods >with the same phase inverter circuit and no grid capacitors? Perhaps >you could do this, Mike, and get back to us with the results. It seems >to me that if cathode bias is universally preferred over fixed bias, a >point in between the two would be better than fixed bias alone. > A buddy of mine has run his Princeton Reverb both ways (Fixed and cathode biased) and he likes the cathode biased arrangement a lot better. He also uses a Deluxe Reverb OT to get more oomph from the amp. Another friend converts all his BF amps over to cathode bias to drop the power and also because he likes the sound and feel a lot better. He just converted over a BF Bassman head that I had converted to 5F6-A specs to cathode bias and the output dropped to about 40W and he says it got much sweeter sounding. And it sounded pretty ok to begin with. I know it's harder on the tranny twins, but I think it can be done fairly reliably as a retrofit if one is careful. Joe From [email protected] Wed Dec 6 10:19:07 CST 1995 Article: 3998 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!newsfeed.internetmci.com!in2.uu.net!panix!not-formail From: [email protected] (Mark Garvin) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender SR--silverface vs. blackface circuit Date: 6 Dec 1995 06:23:49 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 214 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> < <[email protected]> <[email protected]> <[email protected]> <1995Dec1.172547@pomona> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: panix2.panix.com Xref: geraldo.cc.utexas.edu rec.audio.tubes:3998 alt.guitar.amps:6165 I'd like to say up front that if it sounds like I've disagreed with Randy Aiken on a couple of the following subjects, it's really not the case. He just manages to touch on subjects that interest me, so my opinions are a bit more...er...'detailed'. So, Randy--I'll see your 100-line post and raise you 100 lines! >> Mike Kent writes: >> >>I converted an silverface AB568 Super Reverb (mixed cathode/fixed >>bias) to the generally more desired blackface AB763 fixed cathode >>circuit. Sure, the amp is cleaner and more powerful now, but... I >>think I preferred the complex harmonics of the AB568 circuit! >> >>I'd like to hear some opinions about the AB568 circuit, beyond the >>tube book lore about how lousy the silverface amps were. Mark Garvin >>has said in the past that he suspects the phase inverter circuit as >>being a problem, rather than the mixed bias configuration on the >>output tubes. Hi Mike, I've tried to elaborate on the reasons (see below). I was originally referring to the fact that the phase inverter was changed at the same time, so some blame may have spilled over. The 47k phase inverter tends to have a clean, defined sound. Perhaps perceived as thinner than the older 82k/100k circuit. Keep in mind that the AB568 cathode resistors are probably developing under 5 volts of bias. 2 x 150 ohms is equivalent to a shared 75 ohm cathode resistor...not a huge value. And in comparison to true cathode-bias circuits, probably not a huge component of the sound (but still a factor). >>Can anyone comment on their experience with >>modifications to the AB568 circuit? If the silverface circuit is so >>lousy, please explain why. { comment left in, cause I'd also like to hear responses to this. mg } >>[email protected] (Randall Aiken ) wrote: >> >>>As to a "class A" amplifier sounding better and having "touch >>>sensitivity", the reviewers are usually talking about a class AB >>>cathode-biased amplifier and calling it a class A amplifier. Due to I've heard some that some of the same 'reviewers' said that only class AB amps have "touch sensitivity". Quotes preserved here because I think they are referring to bias shift, which has been discussed in your separate thread on blocking. Applies equally well to preamp and power tubes, of course. Obviously, there will be differences in the effects (both pro and con) in a cathode biased amp, since the output tubes will try to resist (no pun) the bias shift. >>>Randy: >>>the negative feedback action of the cathode bias resistor and the >>>shifting of operating point with signal level, these amplifiers >>>generate a richer series of harmonic overtones when driven hard. >>Mike Kent: >>That's what my ears heard when I tried out the AB568 mixed >>cathode/fixed bias over the AB763 circuit. Yet everybody avoids AB568 >>like the plague. Why? >[email protected] (Randall Aiken ) wrote: >I haven't compared the two circuits side by side, so I may be off-base >here, but I tend to agree with Mark Garvin. >There are a couple of points of interest, though. The AB568 uses >separate bias resistors that are bypassed with one capacitor from >cathode to cathode. This creates a degenerate feedback arrangement by >coupling the two cathode signals together for AC signals, and would be >the same (for AC signals) as using a single, unbypassed cathode >resistor for both tubes. I've heard some good pro's and con's regarding the shared resistor. On one hand, some claim that the resistor helps the output tubes to 'stay in balance'. But think about it: the resistor is half the value that it should be for a single tube. So if one tube were pulled out, the remaining tube will be running at double the normal current. Not good. This can occur in normal circuit operation: tubes age, one starts hogging current, the gap widens, etc. Not exactly 'keeping them in balance' is it? >A far better approach would be to use a >separate capacitor for each resistor from cathode to ground, or a >common resistor of half the value bypassed with a large capacitor to >ground. I don't know why this is never mentioned in the books. Intuitively I would have said the same. But I've found that the shared cathode-to-cathode cap is surprisingly effective. No, I don't use it, but I tested it. I'd agree though--best avoid it if possible. I don't see much merit unless you're building a million amps. >In addition, let me clarify my statement about cathode bias shifting of >operating point. Cathode bias actually causes a smaller shift in >average plate current from zero signal to max signal than fixed bias [interesting comments deleted for brevity. Read Randy's article if you missed this]. >Mark's point about the differences in the phase inverter circuit is a >good one. The 47K resistors put the tube on a completely different >spot on the plate curves, and lower the gain. In addition, there will >be a difference in the balance of the two plate waveforms, since the >gain at one side of the phase inverter is larger than the other side, >but the plate resistors are of equal value. Yes, there is indeed a slight imbalance. But there's a reason that Fender stayed with the two 47k's. At least if my math and programming is correct. (I got tired of running the same long series of calcs and wrote a C++ program to confirm math results--all caveats apply) I believe that given the low value plate resistor and relatively high shared cathode resistor, the 'ideal' value for the south-side plate resistor is 49K or so. This was done with textbook-perfect values for 12at7 plate res, mu, etc. Maybe merits jumping to the next std 5% value (51k) but maybe not. Fender certainly thinks about buying volume of one given part, so I'd imagine that helped tip the scales. >In addition, there is a rather large 2000pF cap from grid to ground on >the output tubes. This will roll of the high frequencies quite a bit, >contributing to a difference in tone. They were probably added to >prevent oscillations, so be sure to check for this if you remove them. Ah, another interesting Weber-focal-point. He claims that they will shunt lots of treble. Looks logical, right? If you look back at source impedance and see 47k resistors...or even 82k/100k, then yes--it would start shunting freq's higher than 1600hz or so. But the 11k plate resistance of the 12at7 driver will change the picture. Figure close to 8Khz at -3db. Certainly not as much a factor as it may appear. And no worse than the common 470pf cap across a 12ax7's load resistor. Part of Weber's focus on this cap may be: 1. He never really tested it. 2. Caps to ground are just taboo. 3. He routinely replaces 12at7's with 12ax7's Regarding the latter: he *does* recommend this frequently. And the 12ax7's plate res is significantly higher, so the rolloff would be noticeable. Brings up another question: Why replace the 12at7 with a 12ax7? My math and ears agree on this one: using a 12ax7 cannot boost gain very much in the long-tail driver circuit. Probably less than 1 db at best, even with the 82k/100k circuit. BUT with the 47k circuit, a 12ax7 will actually LOSE gain. Yep, try it and post comments, please. The other voodoo factor in play is that 12ax7's are a bit 'beefier' sounding than the more concise, analytical 12at7. I'm vegetarian, though, so I'm staying with 12at7's for phase inverters. Well, until further notice, anyway. By the way, I routinely remove the .002's but not just to avoid treble rolloff--I try to keep induced phase shifts within a feedback loop to a minimum. Always a good idea. Again, contrary things in play: best not to have any phase shift > 180 degrees. But if a high frequency is going to shift by 180 anyway, best to make sure the open-loop gain at that frequency (probably ultrasonic) is well below unity. Consider the latter kinda tough. We're talking about a relatively high open loop gain. ---------------------------------Along with Weber's and others' recommendations to change Fenders back to the old style phase inverter goes this caveat (posted for the general public, since R.A. knows chapter and verse): Fender changed the phase inverter values for a reason. Tube manuals specify a max dc path to ground from the 6L6 control grids at around 100k. Too much resistance can cause degenerative effects or 'runaway' in the output tubes. The 47k plate resistors are merely an artifact-the REAL objective was to get the bias-feed resistors down to 68k (or 100k in some circuits). This low value of bias feed would have loaded down the previous phase inverter circuit anyway. >Randy: >In conclusion, contrary to what the "experts" with the tube books say, >I think Mark was correct when he stated that the phase inverter >differences probably contribute more to the tone differences than the >150 ohm resistors. Also, don't believe everything you read; if it >sounds better to you with the "bad" circuit, by all means, use it. Thanks, Randy. My own posts aside (of course), I have to say that I've seen more real knowledge of tube amp circuitry on this news group than I have in most 'mod' books. Though I have to admire the nuts to just go ahead and send it to the publisher. >Also, has anyone tried a direct comparison of the two biasing methods >with the same phase inverter circuit and no grid capacitors? Perhaps >you could do this, Mike, and get back to us with the results. It seems >to me that if cathode bias is universally preferred over fixed bias, a >point in between the two would be better than fixed bias alone. I've tested it, but not at very high volume. My interest at the time was to see if I could tell the difference between the sound of the fixed and semi-fixed bias. I hooked up a switch. Not much difference, but at the time I couldn't blast it. I suspect that published comments on the mixed-bias circuit have limited basis in reality, but I'd still like to hear from others about this. By the way, has anyone read the new Vintage Guitar mag? A new Weber mod: tie the two output tube cathodes together and put a single 10 ohm resistor from there to ground. This is to help balance the tubes. He emphasises that this is NOT the same as the 150 ohm Fender resistors since they are separate. Did I read his article correctly? 10 ohms? Regards, Mark Garvin From [email protected] Thu Dec 7 10:40:27 CST 1995 Article: 4016 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!usc!chinews.cic.net!newsfeed.internetmci.com!howland.reston.ans.net!ix.netcom.com!netnews From: [email protected](Randall Aiken ) Newsgroups: rec.audio.tubes,alt.guitar.amps Subject: Re: Fender SR--silverface vs. blackface circuit Date: 6 Dec 1995 20:27:09 GMT Organization: Netcom Lines: 175 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> < <[email protected]> <[email protected]> <[email protected]> <1995Dec1.172547@pomona> <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: atl-ga11-02.ix.netcom.com X-NETCOM-Date: Wed Dec 06 12:27:09 PM PST 1995 Xref: geraldo.cc.utexas.edu rec.audio.tubes:4016 alt.guitar.amps:6190 In <[email protected]> [email protected] (Mark Garvin) writes: > >I'd like to say up front that if it sounds like I've disagreed with >Randy Aiken on a couple of the following subjects, it's really not >the case. He just manages to touch on subjects that interest me, >so my opinions are a bit more...er...'detailed'. > >So, Randy--I'll see your 100-line post and raise you 100 lines! Heh..heh...it's all in good fun and in the best interest of everyone who reads these to have more than one opinion...I just wish more people would join in on these 10K posts - makes good bedtime reading! I don't have time for a feature-length response, so I'll just add my two cents worth in where I think it belongs... >I've heard some good pro's and con's regarding the shared resistor. >On one hand, some claim that the resistor helps the output tubes to >'stay in balance'. But think about it: the resistor is half the >value that it should be for a single tube. So if one tube were >pulled out, the remaining tube will be running at double the normal >current. Not good. > >This can occur in normal circuit operation: tubes age, one starts >hogging current, the gap widens, etc. Not exactly 'keeping them >in balance' is it? Yes, but think of the money they saved in AC30's not having to buy four 200 ohm 5 watt resistors, but just one 50 ohm? :) And besides, Groove Tubes stay matched for the life of the tubes, don't they?? >>A far better approach would be to use a >>separate capacitor for each resistor from cathode to ground, or a >>common resistor of half the value bypassed with a large capacitor to >>ground. I don't know why this is never mentioned in the books. > >Intuitively I would have said the same. But I've found that the >shared cathode-to-cathode cap is surprisingly effective. No, I don't >use it,but I tested it. I'd agree though--best avoid it if possible. >I don't see much merit unless you're building a million amps. > Look for my updated post on this...two resistors are necessary because they changed over from a bias adjust pot to a bias balance pot, and the tubes need separate cathode resistors to develop different DC bias voltages to achieve balanced currents in the output transformer. The cap couples the two cathodes together for AC signals. > >>Mark's point about the differences in the phase inverter circuit is a >>good one. In addition, there will be a difference in the >>balance of the two plate waveforms, since the gain at one side of the >>phase inverter is larger than the other side, but the plate resistors >>are of equal value. > >Yes, there is indeed a slight imbalance. But there's a reason that >Fender stayed with the two 47k's. At least if my math and programming >is correct. (I got tired of running the same long series of calcs and >wrote a C++ program to confirm math results--all caveats apply) > >I believe that given the low value plate resistor and relatively high >shared cathode resistor, the 'ideal' value for the south-side plate >resistor is 49K or so. This was done with textbook-perfect values >for 12at7 plate res, mu, etc. Maybe merits jumping to the next std >5% value (51k) but maybe not. Fender certainly thinks about buying >volume of one given part, so I'd imagine that helped tip the scales. > Yes, the 47K may be right for the lower plate impedance of the 12AT7, but I was referring to the imbalance between plates of the long-tail pair irrespective of tube type and plate resistance. Any tube used as a long-tailed pair will have an imbalance at the plates due to the different path gain from the input grid side. A constant current source will reduce this (the relatively large resistor acts as a poor current source), but generally the two plate resistors are made slightly different, or adjustable. I haven't run the numbers on a 12AT7 vs a 12AX7, so I don't know if they are less sensitive to the imbalance because of the lower mu and rp, but the gain equations have both those variables as well as the plate load resistance in them. >>In addition, there is a rather large 2000pF cap from grid to ground >>on the output tubes. This will roll of the high frequencies quite a >>bit, contributing to a difference in tone. They were probably added >>to prevent oscillations, so be sure to check for this if you remove >>them. >Ah, another interesting Weber-focal-point. He claims that they will >shunt lots of treble. Looks logical, right? If you look back at >source impedance and see 47k resistors...or even 82k/100k, then >yes--it would start shunting freq's higher than 1600hz or so. But >the 11k plate resistance of the 12at7 driver will change the picture. >Figure close to 8Khz at -3db. Certainly not as much a factor as it >may appear. And no worse than the common 470pf cap across a 12ax7's >load resistor. > You are absolutely right, the equivalent source resistance taking into account the internal plate resistance in parallel with the 47K's and the 100K grid bias feed resistors (plus the 1.5K grid stopper) is about 9.7K, which gives about an 8kHz corner frequency, and most speakers are pretty far down by this point. >Part of Weber's focus on this cap may be: >1. He never really tested it. >2. Caps to ground are just taboo. >3. He routinely replaces 12at7's with 12ax7's You forget, this is the same guy who says coplanar traces on a PC board affect the sound too much because of their capacitance (around a few pF, if that?), and that's why point-to-point wiring sounds better. I've used PC boards at 50MHz and more without having too much rolloff; I don't recall guitars having harmonics that high that you need to preserve... >Brings up another question: Why replace the 12at7 with a 12ax7? >My math and ears agree on this one: using a 12ax7 cannot boost gain >very much in the long-tail driver circuit. Probably less than 1 db >at best, even with the 82k/100k circuit. >BUT with the 47k circuit, a 12ax7 will actually LOSE gain. Yep, try >it and post comments, please. The other voodoo factor in play is that >12ax7's are a bit 'beefier' sounding than the more concise, analytical >12at7. I'm vegetarian, though, so I'm staying with 12at7's for phase >inverters. Well, until further notice, anyway. > I'll have to think about this and get back... :) >By the way, I routinely remove the .002's but not just to avoid treble >rolloff--I try to keep induced phase shifts within a feedback loop >to a minimum. Always a good idea. Again, contrary things in play: >best not to have any phase shift > 180 degrees. But if a high >frequency is going to shift by 180 anyway, best to make sure the >open-loop gain at that frequency (probably ultrasonic) is well below >unity. Consider the latter kinda tough. We're talking about a >relatively high open loop gain. You have to roll the gain off at the high end somewhere in the forward path; but, along with the compensation cap's rolloff does come a phase breakpoint....(we won't go into the evils of negative feedback compensation here!) > >Along with Weber's and others' recommendations to change Fenders back >to the old style phase inverter goes this caveat (posted for the >general public, since R.A. knows chapter and verse): > >Fender changed the phase inverter values for a reason. Tube manuals >specify a max dc path to ground from the 6L6 control grids at around >100k. Too much resistance can cause degenerative effects or 'runaway' >in the output tubes. The 47k plate resistors are merely an artifact->the REAL objective was to get the bias-feed resistors down to 68k >(or 100k in some circuits). This low value of bias feed would have >loaded down the previous phase inverter circuit anyway. Fender Silverface facts From [email protected] Sun Jul 2 21:51:41 CDT 1995 Article: 51064 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar Subject: Re: Fender Super Amp Date: 2 Jul 1995 15:34:11 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 25 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com Re your 1970 Super Reverb, you mentioned that this one was made "before CBS changed the circuitry". This is simply not true, if indeed your amp is a Silvereface 1970 model. FYI, and this is WELL documented in NUMEROUS places, CBS bought Fender from Leo in January 1965. At that time, they changed the company name from "Fender Electric Instruments" to "Fender Musical Instruments". They basically left things alone up to the end of 1967, as this was the last year for the "Blackface" amps. Starting in 1968, the Silverface era began. With these 1968 amps, the new CBS-Fender company introduced several circuit modifications, primarily in the phase inverter and output stages, to reduce distortion. This was the dreaded AB568 circuit. The 568 means fifth month of 1968, the design date, just like the beloved AB763 was designed in seventh month of 1963. These 568 amps were the ones responsible for the silverface amps getting such a bad-rap for sounding shitty. Fender quickly realized their error, since sales plummeted, and removed most of the mods. This became the AA1069 circuit. Shortly thereafter, they did some more tweaks, and that was the AA270. Now, if indeed your Super is a 1970, it MUST either be a 1069 or a 270, which most certainly has some CBS changes. This is well documented. Mind you, these amps are fairly easy to modify back to the old 763 Blackface circuit, and they sound way better when this is done. Has yours been modified back to Blackface? Just a bit of Fender history to set the record straight. Regards. Fender Super 60 price From [email protected] Sun Feb 12 16:12:50 CST 1995 Article: 35153 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news2.near.net!news.delphi.com!hollyberry From: [email protected] (Nicole Barr) Newsgroups: alt.guitar Subject: Re: Fender Amp Advice Date: 12 Feb 1995 14:42:30 GMT Organization: Delphi Internet Services Corporation Lines: 39 Message-ID: <[email protected]> NNTP-Posting-Host: bos1d.delphi.com X-To: Nicole Barr In article <[email protected]>, [email protected] (MATT MCGRATTAN) writes: > > Hi, > > I currently have a Marshall JCM900 (the 100W High Gain DReverb 2x12), it > is to big for my current use. (Mainly practice and a little jamming)... > > I have been offered a Fender Super 60 (I think that's it, it's a 60 watt > valvr amp that came out 5 or so years ago... the name temporarily > escapes me...) > > I want to know if anyone can tell me if these things sound good... How > do they stack up to my Marshall... And does anyone have any diea about > how reliable they are.... Hi, kind sir I had a Super 60 for about 4 years and loved it. I think you'll find that it sounds great at any volume, but the amp can get loud. The overdrive isn't very metal either (one of the reasons why I bought it). If you can get your hands on a 1-12 combo, it may be the only amp you'll ever need (but when does NEED ever have anything to do with it). Your problem lies in the relative value of the amps. You have the top of the line (or close to it) Marshall combo. Super 60's regularly come up for sale in Chicago for around $250-300. I've always thought that 60's were a great value in used market. I'm ALWAYS on the used gear prowl, and I've never seen a JCM 900 go for that price. I personally don't care for the amps but would not hesitate to buy one at that price. Actually, I'd have traded for the Marshall, sold it, and bought another Super 60, and pocket the balance. Anyway, I'm rambling. The 60 never failed me in 4 years. In fact, I only retubed it because I felt guilty. It souded great even with two year old tubes. The 60 is great but your Marshall is worth WAY more. DogBoy Fender Super pricing From [email protected] Tue Oct 11 09:40:38 CDT 1994 Article: 25864 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news.sprintlink.net!deathstar.cris.com!deathstar.cris.com!notfor-mail From: [email protected] (Dr.Distortion) Newsgroups: alt.guitar Subject: Re: BLACKFACE SUPER REVERB Date: 11 Oct 1994 02:55:53 -0400 Organization: Concentric Research Corporation Lines: 35 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: deathstar.cris.com X-Newsreader: TIN [version 1.2 PL1] Nick Macris ([email protected]) wrote: : I currently own a perfectly MINT 69' Fender Silverface Super Reverb and : I'm thinking of possibly trading it for a mid-sixties Blackface Super : Reverb. I am specifically using this amp for a bouzouki and I suspect : that I'd get a bit more killer tone out of a blackface. : Does anyone have any realistic opinions on the value of a, let's say, MINT : 65' Blackface Super Reverb? Nick: A MINT '65 Super could be worth as much as $1000 US, maybe even a bit more. (I'm not much attuned to the "vintage" market, I'm afraid). Last year, I bought a '66 in VG condition (I'd give it a 7.5 or 8 out of a possible score of 10) for $700 US, and I THINK it was a good deal, since I usually see higher prices on comparable amps. If it weren't for two replaced speakers and a missing footswitch, my amp would qualify as near-mint. At any rate, I doubt anybody would do an even trade with you for the Silverface. But here's the good news: your '69 Super can sound every bit as good as a Blackface, with a little work. Fender changed the circuit a little when they changed the face panels, but used the same parts as found in the blackface amps. All you need are the schematics and (preferably) layout diagrams for your amp (the '69) and the amp you want to emulate (the '65, also called the AB763). You (or your tech) simply rewire the Silverface to the Blackface circuit. It's actually pretty easy; even a hobbyist of average skills can do it in a day or two. You can get all the info you need in Gerald Weber's "Desktop Reference of Hip Vintage Guitar Amps" book; and, of course, we're always here to answer any questions that come up. I Blackfaced my '71 Super, and I think it sounds every bit as cool as my '66. The '66 looks cooler, I admit, but I use that one at home and take the '71 out to gigs. --Dr.Distortion, New York Fender SuperChamps From [email protected] Sun Nov 20 13:53:04 CST 1994 Article: 32738 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!qualcomm.com!alightonmac.qualcomm.com!user From: [email protected] (Al Lighton) Newsgroups: rec.music.makers.guitar Subject: Re: Superchamp Followup-To: rec.music.makers.guitar Date: Sun, 20 Nov 1994 09:38:31 -0800 Organization: Qualcomm Lines: 35 Message-ID: References: <[email protected]> NNTP-Posting-Host: alighton-mac.qualcomm.com In article <[email protected]>, [email protected] (Keith Spurgeon) wrote: > > I know it's only a toy, but I have a little Fender Superchamp all > tube amp. I need it to piss off my neighbors and my 4 track. > > I recently had a tube job done on it (mostly Sovtek replacements). > The reverb didn't work before the tubes were put in, and now it only works > on "clean" channel. The "lead" channel has no--or very, _very_ little-> reverb. The superchamp uses the Reverb drive, pre-transformer, as its gain boost for the lead channel. It is a very clever use of limited tube gain stages to give a pseudo-channel switching amp, but it does result in the loss of much reverb in lead mode, since it is practically "shorting" the reverb out as a result of tapping off the line prior to the reverb transformer. A mod that I have incorporated into my SC is to put a pot on the rear panel on the cathode bypass resistor of the reverb drive tube. IMHO, the gain of the SC lead channel is too over the top for most uses. Cutting the gain, and compensating by increasing lead channel volume, give a MUCH more useable sound. And it also desensitizes the reverb knob a little, allowing a litle finer granularity of the reverb setting (at the expense of overall reverb levels). I find that I could have just put in a fixed resistor, since I never really turn that gain pot I added all that much. The SC into a big speaker sounds VERY GOOD. It is no toy. Thru the stock speaker, it is a bit wimpy on the bottom end. They were available with an EV option. I'd like to hear one with that speaker. -Al Lighton [[email protected]] Fender The Twin From [email protected] Thu Oct 5 17:15:55 CDT 1995 Article: 4176 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!usc!newshub.cts.com!news.sprintlink.net!howland.reston.ans.net!nntp.crl.com!usenet From: [email protected] (Mike Sirmans) Newsgroups: alt.guitar.amps Subject: Re: Opinions on "The Twin" by Fender? Date: Wed, 04 Oct 1995 21:29:42 GMT Organization: CRL Dialup Internet Access Lines: 83 Message-ID: <[email protected]> References: NNTP-Posting-Host: crl9.crl.com X-Newsreader: Forte Free Agent 1.0.82 [email protected] (B_Phlat) wrote: >Anybody have opinions or specs on this amp? >--Jim I have a Fender "THE TWIN" and simply love it! The versatility is astounding. You can get anything from the sound of an old vintage Fender tweed amp sound (classic Twin) to something akin to the hot sound of a Mesa-Boogie. This is a channel-switching amp, but the audio paths do not go through any solid-state devices, only tubes. You can run both the clean channel and the drive channel in parallel (like I do) and dispense with stomping on pedals to change your tone... just use the volume knob on the guitar. When connected this way, you can drive it hard with the sweet tone like that of SRV or back off and it cleans up real nice with the silky-smooth (twinkly) tube harmonic top end. THE TWIN may be run as a 100watt/25watt combo by using all 4 stock output tubes. The reduction in power is achived by tapping the power-supply from either a full-wave bridge (460 volts) or using a half-wave bridge (236 volts). The manual also says that you can pull 2 of the output tubes (which is the way I run mine) and set the impedance selector to 1/2 the original value... Remember: 1/2 the tubes - 1/2 the load. The two 8-ohm speakers are wired in series for a total of 16-ohms... When running with only 2 power tubes, you must set the selector for 8-ohms into this load. Access is provided on the back panel of the amplifier to set the idling bias current for the power tubes and to set the balance between the upper and lower pair (in the push-pull circuit). The fine print on the back of the amp says that you should set the meter to read .040 volts (40 millivolts) which is read across a zener-protected precision 1-ohm resistor in the power stage cathodes. If you remove 2 of the tubes as I did, it should read 20 millivolts. You can bias the amplifier yourself using any good Digital MultiMeter. The Fender THE TWIN even has a built-in red-box (a low-impedance floating 600-ohm tap) taken directly from the output transformer suitable for driving recording consoles or sound-reinforcement equipment. All-in-all a pretty cool amplifier. The speakers are premium Fender blue label speakers with huge magnet structures. They DO contribute to the overall weight however. Now for the downside... THE TWIN is heavy. 75-80 pounds heavy. Get a full-time roadie. Also, it has a lot of tubes. Four 6L6's (use Groove-Tubes 6L6's or the russian 5881's), two 12AT7's (use NOS Fender, Phillips, or Sylvania), and five 12AX7's (Use hand-picked Chinese tubes that are not microphonic. That's right... avoid the Sovteks, they have a tight sound which may be good for a brittle Marshall... but are not sweet and buttery like an old Fender. The Chinese tubes are OK for this because they will 'break-up' at lower drive levels. They also have a larger internal structure, which contributes to a fatter tone... but you DO have to get hand pick some good ones. If you can't afford the time or trouble to do this... get Groove Tubes or Ruby to do it for you). DO NOT substitute 12AX7's for the two 12AT7's... the AX7's cannot handle the 400+ volt plate potential without self destruction. Also it has red knobs (some folks don't like the looks). On the upside, it uses fairly common tubes and can be used in just with just a single pair of output tubes. It has the large Accutronics spring reverb which is just dripping with tone. It has 100% tube circuitry, including the preamp-send/poweramp-return effects loop. Also it has red knobs (some folks like the looks). They will have to pry mine loose from my dead fingers to get it away >from me... it LIKE it that much. ''' (o o) .---------oOOO---(_)-----------------------. | Mike Sirmans [email protected] | | USCWCMGS at IBMMAIL | | 72117,3177 Compu$erve | | Fidonet 1:133/8004 | `------------------------------oOOO--------' |__|__| || || ooO Ooo Fender Tone Circuit From [email protected] Fri Oct 13 11:18:27 CDT 1995 Article: 4368 of alt.guitar.amps Newsgroups: alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uunet!in1.uu.net!news.sprintlink.net!newsfeed.internetmci.com!howland.reston.ans.net!ix.netcom.com!netcom.com!netcom7.netcom.com!ftom From: [email protected] (Tom May) Subject: Re: How to compute tone control response: was Marshall "sweep" control In-Reply-To: [email protected]'s message of 5 Oct 1995 17:54:26 -0400 Message-ID: Sender: [email protected] Organization: The Planet Eden References: <[email protected]> <[email protected]> Date: Fri, 13 Oct 1995 05:39:22 GMT Lines: 111 Somewhere down at the bottom of this, I offer an interpretation of what I believe the typical Fender/Marshall tone controls are *really* doing to the frequency response. But first, this word from our sponsor, Mark Garvin: In article <[email protected]> [email protected] (Mark Garvin) writes: >.... Hi again, Tom. This is the one I was thinking about. It >just changes the pivot point in the tone stack. In other words, it >will shift the notch frequency upward and at the same time it will >lessen the depth of the notch. A side result is that the bass and >middle controls will have less effect. >Back to the sweep control, consider the simplified version of that ckt >with the treble and bass controls up full, mid at 0. This is the >classic mid-cut (notch) circuit that most tone controls 'condense' >to when considered closely. > > | | Ct >from plate> -----------| |----------------> to vol control >|||| >\\ > / Rb / Rt >\\ >// >|| > --------------->| > ----- Cb > ---->| >| > ----> -->[... Mark analyzes the hell out of this circuit before our very eyes ...] >so the center frequency is 295.1 Hz (whew!) > >Note that these values are not exact, because from the start, >I chose to simplify the 'voltage dividers'. The actual attenuation >and formulae should have been: > > 250k >----------- etc. > 250k + Xc >This requires a lot more complex equation. I believe that the Fender >controls actually balance closer to 320hz. Big deal. Mark, I spiced this thing (Fender Twin Reverb AB763 TABv3 p.483) up good and your numbers for the -3db points and notch frequency are right on even with all your approximations. Nice analysis, very impressive and enlightening when I took the time to understand it and draw even further reduced circuits for high and low frequencies. When I included a non-zero source impedance on the input side, a finite load impedance on the output side, and threw in all the parts you threw out, it only made a difference in about the third significant figure. The notch is indeed at 295Hz. In general, the non-zero source impedance cuts highs (it is a divider with Rb), and the finite output impedance cuts lows (it is a divider with Rt). In the Fender circuit, the cuts are about equal so the whole response drops fairly evenly. >Writing a program to do the math above would be pretty easy. Then >just vary Rb and see the resultant curve: As Rb gets smaller, the >notch frequency will move upward and the attenuation in midband will >decrease. Yes, that is what I saw, but the other equally important effect is that as Rb is decreased the treble response really falls off as the treble gets shunted to ground through Rb and Cb. When Rb gets on the order of 5K or so the "notch" appears more like this: __ \ \ \ ____ \/ Not a Good Thing. My new grokking of the Fender/Marshall type tone control is now: Turning up the bass and treble *increases* the bass and treble frequencies from a flat response, leaving a notch in the middle. The corner and notch frequencies can be calculated like you said. The midrange control is not *really* a midrange - it sort of sets the "floor" for the whole response (not surprising from its position at the bottom of the whole tone divider circuit) - as it is turned up, it tries to compress the whole frequency response upwards to a flat line, with the greatest affect (most compression) on the most deeply cut frequencies. Since these are usually the frequencies in the notch, this means it is usually turning up the midrange, but it is just as capable of turning up the bass and treble when those controls are turned down. The midrange control cannot boost the notch frequencies high enough to flatten the response, though; the only way to get a flat response is to turn the bass and treble all the way down to eliminate the notch. The corollary to this is that turning up the midrange will *not* boost the mids *above* the bass and treble. I've got this weird feeling that I would have been better off not knowing all that, but too late now :-) And Rb, the "sweep" control? You're right, it looks better to change the corner frequencies by adjusting Ct and Cb because of Rb's deleterious effect on the treble. (Note that the 100k Fender value actually seems to boost the highs somewhat; 50k gives a flatter bass/treble balance in simulation). -Tom. From [email protected] Mon Nov 27 16:47:41 CST 1995 Article: 5850 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.eas.asu.edu!news.asu.edu!ppp2-13.INRE.ASU.EDU!PYLOT From: [email protected] (Ruth and Dale VanZile) Newsgroups: alt.guitar.amps Subject: Re: Tone circuits: part 3 Date: Sun, 26 Nov 1995 13:03:29 Organization: Arizona State University Lines: 25 Message-ID: References: <[email protected]> NNTP-Posting-Host: ppp2-13.inre.asu.edu X-Newsreader: Trumpet for Windows [Version 1.0 Rev A] In article <[email protected]> [email protected] (Mark Garvin) writes: >Please try to post follow-up queries. No problem with email generally, >but I will not have as much time to reply to separate email questions. >This post has already taken long enough. Darn ASCII diagrams. >Anyway, I hope this has helped to answer a few of the email queries. >Sorry for the delay. I think also that the Fender circuit has a bit less insertion loss. I'd be interested to see your thoughts and analysis on the Hiwatt tone circuit and the 6G7 Fender Bandmaster. I've done some freq. response analyses on these circuits using a program called "ECAP". The Hiwatt actually has a bit of a mid-boosting action to it in the area of 400Hz to 2500Hz (estimated #s, as it's been a while since I ran the circuits) or so, along with a serious scoop at about 300Hz. The 6G7 has a big dip at about 800 Hz, and both have better bass response than the later Fenders. IMO, they are really nice sounding circuits. The 6G7 sounds brown and almost Marshall-esque, and the Hiwatt is crisp but still packs some punch in the lows, along with a "clean" sounding low mid area. Do you have a print of these? I can send a copy of each if you need it. Or, if you're in the NYC area, I can drop one off over the holiday break, as I'm going to be back that way for a wedding.... Dutch From [email protected] Wed Nov 29 00:29:58 CST 1995 Article: 5911 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!newsfeed.internetmci.com!newsxfer.itd.umich.edu!umcc.umich.edu!news.eecs.umich.edu!panix!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: Tone circuits: part 3 Date: 28 Nov 1995 21:05:16 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 76 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com In <[email protected]> [email protected] (Mark Garvin) writes: >TONE CIRCUITS, PART 3. Fender controls vs hifi controls. >----------------- BASS and TREBLE BOOST (MID CUT) -----------------> In >---+------------------------------- >|| >/| > / R1 --> / --- C3 >/| > | R4 | > +--------------//////----------+--------> Out >| > --> --- C2 >| >/ > / R3 >/ >/ >| > ----> -->By the way, assuming that the 'left' and 'right' R-C sections do not interact (left RC net is low impedance compared to right-side RC net), the center frequency (and therefore the attenuation) can be approximated as: 159000 -----------------------------_ /-------------------------- <-attempt at square root symbol \/ R1 * C2 * R4 * C3 where Cap values are in microfarads R3 is ignored, since it is usually small compared to R1 >----------------- BASS and TREBLE CUT (MID BOOST) -----------------> In >---+ >| >/ > / R1 >/ >/ >| > --- C1 > --> | R4 > +------//////-------+--------> Out >|| > / --> / R3 --- C4 >/| >/| >|| > ----- ----> --- -->-Pretty much the same here, ignoring R1 159000 -----------------------------_ /-------------------------- <-attempt at square root symbol \/ C1 * R3 * R4 * C4 >Mark Garvin >Composer/Design Engineer >New York City Fender Tone Circuits From [email protected] Sat Dec 2 09:27:48 CST 1995 Article: 6039 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news.nic.surfnet.nl!sun4nl!EU.net!newsfeed.internetmci.com!in2.uu.net!panix!notfor-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: Tone circuits: part 3 Date: 2 Dec 1995 05:08:07 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 41 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: panix2.panix.com In <[email protected]> [email protected] (Mike Rejsa) writes: >*Many* thanks to Mark for his in-depth treatment! >Minor question: Is there any effective difference between the 250pf/0.1/.047 >Fender setup and the 250pf/.022/022 Marshall version? (Pots are different >too, of course...) Hi Mike, If the 'slope' resistor (100k in the Fender circuit) and the treble pot (250k) stay the same, then the center frequency of the: 250pf/.047 circuit is around 295 hz with about a 19.7 db mid cut 250pf/.022 circuit is around 430 hz with about a 16.8 db mid cut The numbers above are derived using simplified versions of the tone circuit which I outlined in a follow-up post. No guarantee on accuracy, since I'm rushing this. The .022 circuit gives the bass control wider range, because like all simple R/C nets, these are limited to 6db per octave. Placing the notch frequency a bit higher affords about 2-1/2 octaves down to the guitar's low E string (82.4 hz). The standard Fender .047 circuit's mid notch is less than two octaves up from the low E string, so the low E cannot be 'boosted' be even 12 db. The other (.1) cap (at the top of the bass pot) is primarily DC-blocking, since the reactance is still relatively low down to bass frequencies. Changing to .022 doesn't make that much difference, esp in the Marshall circuit with a 1 meg bass pot. Nor does the value of the bass pot enter into the center frequency calculation very much. It DOES work as a voltage divider against the 100k slope resistor, so values over 250k don't do a whole lot of good. In fact, if a 1 meg pot is used there, best make sure that it's a true log taper (1/10th of the value at half-rotation) rather than a semi-log (usually around 1/3rd at half-rot.). Otherwise all the bass boost will happen in the low range of the pot...no audible effect with further rotation. Mark Garvin Fender Transformer Codes From [email protected] Sat Jan 13 19:10:03 CST 1996 Article: 77538 of rec.music.makers.guitar From: [email protected] (THOMAS BREMER) Subject: RE: Silverface Deluxe Rev Questions Date: 13 Jan 96 08:35:11 -0800 References: <[email protected]> Message-ID: <[email protected]> Path: geraldo.cc.utexas.edu!cs.utexas.edu!atlantis.utmb.edu!news.tamu.edu!bloombeacon.mit.edu!newsfeed.internetmci.com!news.sprintlink.net!news.msn.com!msn.com Newsgroups: rec.music.makers.guitar Organization: The Microsoft Network (msn.com) Lines: 34 Heres a quick way to date Fender amps ('60-82). View the underside of the chassis (flashlight helps alot)look for the reverb driver trans. Its in the middle of the 6 preamp tubes with the removable shields. You'll find 2 rows of numbers, top set is the Fender part #, always starts with a 022, in this case it would be 022921. The bottom set is the date code. Works as follows, they have 6 numbers, first three is the EIA manufacturer, ignore this. The last three tell you the year and week. Example-606423. For a black face, this transformer would have been made in 1964 during the 23 week (---423) The trick to this is they don't renumber the decades. A silverface made on the 23rd week of 1974 will have the same date code. The only good thing about dating amps this way is Fender never deviated-still valid today. I use this before buying a amp always-check all four transformers-will tell you if there has been problems along the way. Very rare to find different year trans. in any Fender products. If your JBL says D120F on it(look for the "f") certainly could have been stock. On the bottom lower corner of the grill cloth was/is a 1x2 inch "JBL" plastic logo that Fender attached. By 1968 deluxes usually left with CTS/EMINANCE speakers (Jensen had closed down) Once in awhile you can see the EIA code, CTS-starts with a #137-sometimes these are under the doughnut fender speaker label. Dating system for transformers works on the speakers also. Fender used two kinds of silver/blue grill cloth, first version, as with your amp, the blue stripe fades away to red, then brown and eventually disappears. The last version had a super bright neon blue which held its tint. Remember that Fender dealers could order any of the silverface amps with black faceplates and regular 60's silver grill. ($50.00 additional at that time) Always pull on the volume controls to see if they pull out-these were pull boosts, not labeled on 70's faceplates. Bremer Fender Treble Caps From [email protected] Tue Jul 23 23:41:27 CDT 1996 Article: 19358 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!usc!newshub.csu.net!newshub.sdsu.edu!newsfeeder.sdsu.edu!nntp.primenet.com!news1.best.com!news.sgi.com!news.msfc.nasa.gov!newsfeed.internetmci.com!newsxfer2.itd.umich.edu!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: Mica caps for smooooth top-end! Date: 23 Jul 1996 19:30:29 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 21 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: newsbf02.mail.aol.com In article <[email protected]>, [email protected] (Fulltone) writes: >Any of you guys notice the nice change in quality of the high-end when you >change-out your treble cap (250pf.) in a Fender Reverb amp? >Even silver mica seems to help. Mike Fuller I have done some experimenting with silver mica caps, they definitely seem to open up the top end, however, it is usually a bit too much for me on Fender Reverb amps. I have found them to be a very effective way to brighten up dark sounding amps. I have also tried them in JMP Marshalls, replacing the 470 or 500pf cap that bypasses the 470k resistor between the 2nd gain stage and the tone stack. I incoporated this into a Marshall hot rod that the client wanted to sound like his Dumble OD Special. Ok, it'll do Robben Ford now... Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. Fender Tube Chart Dates [email protected] (Dave Johansen) Re: Silverface Super Rvb -- a bunch of naive questions 23 May 1994 18:23:01 GMT cisco Systems, Incorporated Newsgroups: rec.music.makers.guitar References: <[email protected]> dd jIn article <[email protected]>, [email protected] (LeftyGtr) writes: |> In article , [email protected] (John F |> Duesenberry) writes: |> |> so, |> or is this just par for the course with old amps? |> |> Oh, and another pesky question: is there any way I can verify how |> old this thing is without ripping it apart? |> |> ---------------|> |> The easiest way to date a Fender amp is by the serial number |> impressed into the right side of the rear chassis, and the speaker |> date codes. (This is provided of course the speakers have not been |> changed.) |> Not according to Fender, They use the ink stamp on the tube chart, Just verified the '66 Blackface I just bought using that method.. PS THey also said that the serial number on the chassis is NOT reliable.. just for you FYI |> By 1972 a Super Reverb would have a master volume, so yours would be |> somewhere between '66 and '72. |> |> $650 is a fair price to pay for a Super Reverb in good working order. |> At least in L.A. |> |> No, old amps don't just do that... Your hum problem sounds like a |> simple enough thing to fix. There are several causes for this, none |> of which should be expensive to rectify. Keep in mind that you don't |> have to replace all of the tubes simply because you walked into a |> repair shop. Take it to a repairman you trust. |> Have your filter caps checked... |> Post the serial number, or at least the first 3 digits and X's for |> the rest, and I'll be happy to date it for you. If there are codes on |> the speakers, include them as well. |> |> Scott Jennings |> Route 66 Guitars, U.S.A. There are two capital letters stamped on the tubechart.. mine say PJ P = 1966 J=October, First letter is the Year, and second is the month.. Here is the chart below, as stolen from Aspen Pittman's Book... A = 1951 A = January B = 1952 B = February C = 1953 C = March D = 1954 D = April E = 1955 E = May F = 1956 F = June G = 1957 G = July H = 1958 H = August I = 1959 I = September J = 1960 J = October K = 1961 K = November L = 1962 L = December M = 1963 N = 1964 O = 1965 P = 1966 R = 1967 I don't know how far the years go, but we'll stop at '67 for now.... Good Luck, Dave Johansen Fender Vib Rev Pedal From [email protected] Tue Jan 23 07:36:02 CST 1996 Article: 78675 of rec.music.makers.guitar From: [email protected] (THOMAS BREMER) Subject: RE: WTB: Fender rev/vib footpedal Date: 23 Jan 96 05:49:10 -0800 References: <[email protected]> Message-ID: <[email protected]> Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!vixen.cso.uiuc.edu!newsfeed.internetmci.com!news.sprintlink.net!news.msn.com!msn.com Newsgroups: rec.music.makers.guitar Organization: The Microsoft Network (msn.com) Lines: 5 Thomas: You can get two button footpedals as a new item from your local Fender dealer part#0037211 000. You'll have to wire the RCA plugs on to the cable. Tom Bremer Fender Vibrato Ticking From [email protected] Sat Mar 23 15:47:46 CST 1996 Article: 11785 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!usc!elroy.jpl.nasa.gov!news.msfc.nasa.gov!news.ingr.com!imci4!newsfeed.internetmci.com!news.west.net!term13.sb.west.net!user From: [email protected] (Tom Phillips) Newsgroups: alt.guitar.amps Subject: Re: vibrato fix for Fender Pro Reverb Date: Fri, 22 Mar 1996 09:50:01 -0700 Organization: TJI Lines: 45 Message-ID: References: <[email protected]> NNTP-Posting-Host: term1-21.sb.west.net In article <[email protected]>, theodric@ (Theodric Young) wrote: > I just got a blackface 70 Watt Fender Pro Reverb (1981 I believe). When > I checked it out at the store, there was a ticking sound in the output > that could be heard when the master volume knob was turned up.... > > At first, the guys at the store said they would fix that under > warranty. However, after consulting with their amp repair guy, they > now say that that ticking is present in all of those particular amps. > The problem, they say is that the plate wire is too colse to the grid > wire on one of the tubes. They can fix it, supposedly, by installing > a capacitor somewhere, although it comes under the category of a > modification, not a repair, so I'd have to pay for their labor. > > This ticking really isn't all that loud and I could certainly live > with it, but I'm curious as to whether or not anyone else has ever > come across this, and if so, how they fixed it. > > Also, if anyone knows where I could get ahold of schematics for this > amp, I'd greatly appreciate it. > > Thanks in advance. > > -Theodric Young > The ticking is a common problem. It can be often be reduced by redressing the wiring. Silverface amps are usually worse than blackface which had neater wiring. The ticking can usually be eliminated by installing a 0.01 µF cap from one side of the LDR assembly to ground. The cap goes on the side that is connected to the 10 Meg resistor. This fix is described in Weber's book which also includes schematics (Along with his personal opinions on everything. The reader needs to sort out the facts from the hype). If you are not comfortable working on your own amp then any good tech should know about this fix. IMHO the store should have fixed this under warranty as promised. It's no big deal. I think Fender even put out a service bulletin describing the fix. Good Luck, Tom Phillips From [email protected] Sat Mar 23 15:48:22 CST 1996 Article: 11792 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!utnut!torn!csn!news1.csn.net!imci3!imci4!newsfeed.internetmci.com!EU.net!Norway.EU.net!nntp-oslo.UNINETT.no!nntptrd.UNINETT.no!nntp.uio.no!news.cais.net!netaxs.com!mhv.net!bbs.mhv.net!Dr.Distortion From: [email protected] (Dr Distortion) Newsgroups: alt.guitar.amps Subject: Re: vibrato fix for Fender Pro Reverb Date: 22 Mar 1996 20:50:29 GMT Organization: MHVNet, the Mid Hudson Valley's Internet connection Lines: 17 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: csbh.mhv.net X-Newsreader: TIN [version 1.2 PL2] Theodoric, That ticking you hear is a common problem. It's caused either by HF hash >from the neon bulb in the tremolo optocoupler, hash from the oscillator circuit itself, or a combination of both. The leads that carry the preamp signal to the input of the phase inverter are perilously close to the trem circuit, so unwanted coupling occurs easily. A good tech can improve the situation substantially by cleaning up the lead dress around the tremolo and phase inverter circuits. Also, that .02 cap you often see placed across the neon in the silverface amps can make a big difference. The cap is of a large enough value to help shunt HF hash, but small enough that it doesn't form an accidental relaxation oscillator with the neon :) At any rate, make sure your tech has experience with old Fenders. This is a common problem which an experienced tech can rectify without much trouble in most cases. Guys who don't have a good grasp of these circuits are likely to be left scratching their heads for hours, on the other hand. Fender Vibro King circuit From [email protected] Sat Aug 6 10:19:24 CDT 1994 Article: 21888 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!pipex!sunic!ugle.unit.no!trane.uninett.no!eunet.no!nuug!EU.net!uunet!news.sprintlink.net!deathstar.cris.com!deathstar.cris.com!notfor-mail From: [email protected] (Dr.Distortion) Newsgroups: alt.guitar Subject: Re: Fender Vibro King Date: 6 Aug 1994 09:12:55 -0400 Organization: Concentric Research Corporation Lines: 46 Message-ID: <[email protected]> NNTP-Posting-Host: deathstar.cris.com [email protected] (Jim Collins) wrote: CO>fat. I love it. Anyway, the biggest knock on the amp when it first came CO>out was that the FAT feature was not footswitchable. Imagine my surprise CO>when I unboxed the beast to find that our friends at Fender have been CO>reading their mail. The FAT feature is now footswitchable. The amp comes CO>with the same dual footswitch that the reissues come with, only the two CO>features that are footswitchable on the Vibro King are the tremolo and the CO>FAT. Reverb is not footswitchable. I have studied the schematic for the Vibro-King at length, and it might be of interest to the more technically inclined readers of this group that the famous FAT switch is nothing more than a switch that grounds a 22 uF bypass capacitor across the cathode of the first gain stage. This is an OLD trick, although I'm not implying that that makes it any less useful. A good tech could convert the #2 input jack into a footswitch jack for the FAT function in minutes... something you owners of Vibro-Kings might want to consider, once your warranty expires. It's also easy to make the reverb footswitchable without altering the amp in any way. All you need to do is rig up a pedal to ground the hot lead of the return from the spring tank. You could use a "Y" adaptor to hook up the switch in parallel with the reverb return cable. Here are some more comments on the Vibro-King's circuit: 1) In a break with Fender tradition (at least Fender tradition since the late '50s), there is NO negative feedback loop. This might explain why the amp is gaining a reputation for volume and harmonic richness. 2) The reverb section is NOT an exact copy of the old standalone Fender reverb unit, although it's close enough. It uses a 6BQ5 for the reverb driver and one triode preamp before the driver, unlike the original with two triodes before the 6K6 driver. The recovery circuit is also slightly different. But like I said, it's close enough; it embodies the overall "spirit" of the original. 3) The tone stack is an inspired variation on the old "Blackface" circuit. It uses a 150 pF treble cap instead of 250 pF (something I've been doing to my stock Fenders for a while, since I think the 250 pF emphasizes the high mids too much) and a larger-value midrange pot (25K, I believe, although I don't have the schematic handy). The volume control comes BEFORE the tone stack, and is separated from it by the second gain stage. The treble pot wiper is connected (via a coupling cap) to the grid of the phase inverter. Overall, it's a surprisingly simple circuit. --þ OLX 2.1 TD þ /\/\Dr.Distortion/\/\/ , New York Fender VibroVerb From [email protected] Mon Mar 20 10:09:06 CST 1995 Article: 44367 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!gatech!newsjunkie.ans.net!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: rec.music.makers.guitar Subject: Re: Vibrolux Reverb = Vibroverb? Date: 19 Mar 1995 23:04:27 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 23 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com A Vibrolux Reverb is not the same as a VibroVerb. The Vibrolux is a 35-ish Watt 2 x 10 amp. These things can sound great when properly set-up. This includes proper biasing of the output stage. The VibroVerb came in two flavors. The first was in Brown Tolex in 63, and was also a 2 x 10 amp. These are very much collector items, and they sound great. When the Blackface era started, the VibroVerb became a 1 x 15 amp, and they also increased the internal operating voltages a bit, so it used the same power transformer as the Super Reverb. The blackface Verb has the same chassis size as a Super, which is somewhat larger than a Vibrolux. These Black VibroVerbs sound totally killer if you like a very fat clean tone. The most famous user of these amps was SRV. Look at his Live at the El Mocambo video, and you'll see one behind him (along with a Blackface Super Reverb). I've worked on one that had the optional JBL D130, and was blown away with the tone. It is LOUD and punchy as hell. The low-end response is to die for, and it also has suprisingly good high end, way more than you would expect from a big-ass 15. These amps are not for the high gain, high disdtortion death and thrash metal crowd. Since these Blackface VibroVerbs are very rare, an example in excellent condition will sell for about $2000. Gotta love those 15s!! Regards. Fender Vibrolux RI review From [email protected] Thu May 11 13:34:14 CDT 1995 Article: 50883 of rec.music.makers.guitar Newsgroups: rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!uunet!tandem!pc6-54.atg.tandem.com!user From: [email protected] (Jim Collins) Subject: Re: New Vibrolux? Message-ID: Followup-To: rec.music.makers.guitar Sender: [email protected] Nntp-Posting-Host: pc6-54.atg.tandem.com Organization: Tandem Computers, Inc. References: <[email protected]> Date: Wed, 10 May 1995 18:20:51 GMT Lines: 59 X-Disclaimer: This article is not the opinion of Tandem Computers, Inc. In article <[email protected]>, [email protected] (William G. Sacks) wrote: > > Has anyone had a chance to play with the new Vibrolux mentioned > in the GP? It certainly sounds good on paper... I just picked up a new Vibrolux Reverb. It is a terrific amp, but like anything that is vintage-inspired, it isn't for everyone. First of all, the amp is not a reissue. It is inspired by vintage-style amps, but this exact set of features was not found on any Vibrolux in the past. It is a 40 watt, 2x10 combo amp, all tube, although it has a solid state rectifier. This is not replaceable by a rectifier tube, as in the Bassman, but built-in, like the Vibroverb reissue. It has the traditional Fender spring reverb (one control, not like the three-control Vibro King), although this reverb is not as lush as the reverbs found on the Vibroverb, Twin Reverb or Deluxe Reverb (all reissues). I get plenty of reverb for my tastes, though I have to turn it up farther than on other Fender amps. I would suspect that surf music players, fans of Dick Dale, may find that there isn't enough reverb, but anyone else who just likes a touch would find it perfect. The tremolo is excellent, if you like that sort of thing (I do). I can't remember what type of tremolo it is, but it is the type that has not been used since the early '60s. Very deep tremolo. (Oscillating something or other.) The amp does not have a master volume, high gain mode, channel switching, or an effects loop. (Thus, the earlier comment about this amp not being for everyone.) The amp does have the traditional Fender two channels, one normal and one bright. Each channel has the tradition two inputs, with the first input 6dB hotter than the second, for that channel. This amp differs >from vintage Fender amps in that old Fender amps usually only provided reverb and tremolo on one of the channels -- if the amp had normal and bright, then reverb (and usually tremolo) would only be available on the bright channel. The new Vibrolux Reverb has reverb and tremolo on both channels -- the reverb and tremolo controls affect both channels. Each channel has volume, treble and bass controls. The amp is cream colored Tolex with ecru grille cloth. It has a brown face, and white knobs. It has the same Fender logo as is on the Vibroverb. It also has tilt-back legs. So, how does it sound? This amp was born to play with a Telecaster. Very strong Tele tones, very much remeniscent of early Roy Buchanan. A Tele is a very bright guitar, and many amps just come off too shrill with a Tele. This one is voiced beautifully for single coil pickups. A Stratocaster also sounds terrific through this amp. I find myself using the bridge pickup of my Strat a lot more than with other amps. (The Strats used are wired in the traditional fashion which does not provide a tone control for the bridge pickup.) I also find that I can get a tone I really like without having to turn the amp up way up. This is a bonus. Because the amp appears voiced for single coils, a humbucker-equipped guitar has a harder time dealing with this amp. A Les Paul seems to overpower the amp too soon. You really have to back the bass off and boost the treble to make a Les Paul work, here, but even so, it overdrives too easily for my tastes. It seems harder to get a nice, clean tone out of the humbuckers. I will admit, though, that the Teles and Strats sound so good through it that I've been spending most of my time playing them instead of the Les Paul. That's about it. Jimmy Fender Was Dumb From [email protected] Tue Apr 22 12:50:08 CDT 1997 Article: 29172 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!news-peer.sprintlink.net!sprint!newspull.sprintlink.net!news.sprintlink.net!news-chi-13.sprintlink.net!news.azstarnet.com!news From: [email protected] (Gerald Stombaugh) Newsgroups: rec.audio.tubes Subject: Re: Leo Fender was dumb, but lucky. Date: Tue, 22 Apr 1997 15:43:59 GMT Organization: Starnet Lines: 60 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: usr12ip22.azstarnet.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Newsreader: Forte Agent 1.0/32.390 Xref: geraldo.cc.utexas.edu rec.audio.tubes:29172 On Tue, 22 Apr 1997 12:05:17 GMT, [email protected] (Dave Cigna) wrote: > >Bill Bolton wrote: >>[email protected] (Dave Cigna) wrote: >> >> >Mythical Belief #1: > Great vintage guitar amps sound the way they do because they are > built from cheap, underrated components that are pushed beyond > their specifications. The result is magical and could only have > been arrived at by dumb luck. > >Mythical Belief #2: > The builders of great vintage guitar amps were basically clueless > idiots that more or less just copied schematics from tube manuals > and hoped for the best. They thought they were building hi-fi amps, > but luckily for us, they were too stupid to be successful and > ended up with great sounding guitar amps completely by accident. > > The truth as I knew it. Leo Fender was very demanding and knowledgable in his requirements for his amplifiers. I designed power and output transformers for Leo and others in the industry for 36 years. A consumer product certainly has to be designed with cost in mind, but all producers pushed every vendor for an improved product at a reasonable price. For instance: Leo used to buy speakers from Jensen when he could have paid less elswhere but only Jensen could last a reasonable length of time for this test. Plug a 16 ohm 15" whoofer into the 120V line and see how long it will last. Ohms Law says 120V x 120V divided by 16 equals 900 WATTS. power. The life of the speaker is listed in seconds rather than years and you learn a whole lot about that speaker. Fred Mergner was the Chief Engineer of Fisher Radio and George Meyerle was Chief Engineer of Harmon Kardon. Those two gentlemen were so demanding concerning the sound quality of an amp that they drove their vendors to frustration. You would be innovative, progressive and COST EFFECTIVE or they would find someone who was. The TV people, especially Magnavox were intensely interested in sound quality even in their normal TV receivers. The wonderful part of that era was that it was designed here, produced here and enjoyed world wide. Our economy today would be infinitely better if we were again designing and producing consumer items. Jerry Stombaugh [email protected] time Fender amp tremolo From [email protected] Mon Jan 31 23:00:39 CST 1994 Article: 13823 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!decwrl!morrow.stanford.edu!morrow.stanford.edu!mueller From: [email protected] (Fritz Mueller) Newsgroups: rec.audio.pro,rec.music.makers.guitar Subject: Re: Tech help w/ Fender twin not tremoling Date: 30 Jan 94 23:37:54 Organization: Stanfnord Lines: 49 Message-ID: References: <[email protected]> NNTP-Posting-Host: hpp-ss10-1.stanford.edu In-reply-to: [email protected]'s message of 24 Jan 1994 18:57:49 GMT Xref: geraldo.cc.utexas.edu rec.audio.pro:7131 rec.music.makers.guitar:13823 >> HELP! I'm working on a Fender Twin that's working fine other than >> the tremolo. ... What does the tremolo circuit look like, and how >> does it function? The trem circuit in those old fenders is an RC phase-shift oscillator -- three cascaded RC stages in a feedback loop between the plate and grid of one of the triode tube sections. The rate of oscillation is controlled by varying the resistance of the "R" leg of one of the stages; the trem is disabled/enabled by breaking/making the ground connection on one of the legs. The oscillator is buffered through another triode section and coupled onto the power tube grid bias supply via a neon-lamp/photoresistor gizmo. You can find the trem circuit by tracing back from the trem speed pot or from the trem pedal RCA jack, or just look for the three ceramic disc caps connected end to end (usually two .01mf and a .02mf.) Most often these stop working for one of three reasons: - The caps get leaky. If the circuit oscillates very briefly and damps out after a cycle or two when you switch it on and off, this is probably the problem. Just pull 'em and replace 'em. (Note that these caps may read fine on a capacitance meter even though they're leaky, unless you have one of the cool old "magic eye" type cap meters!) - One of the RC sections has a bad ground connection. Note that this includes the leg whose ground connection is used for switching the trem on and off! Most old fenders won't trem without a pedal or a dummy shorting plug installed in the pedal connector. - The neon-lamp/photocell gizmo flakes out. If your 'scope shows the circuit is oscillating at the grid of the buffering triode section and you still have no trem, then this is the culprit. You should be able to see the neon bulb winking at you if everything is working correctly. It is not uncommon to find that these gizmos fail because of a short between the leads of either the neon bulb or the photoresistor beneath the heat shrink that the thing is wrapped in; this can usually be corrected by spreading the offending leads with a dental pick or other suitable instrument (discharging the power supply caps first, as always, of course!) Hope this helps! --FritzM. Fender bad Supers From [email protected] Sun Jul 2 21:50:55 CDT 1995 Article: 51065 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar Subject: Re: Fender Super Amp Date: 2 Jul 1995 15:42:38 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 17 Sender: [email protected] Message-ID: <[email protected]> References: Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com The NEW Fender Super is most certainly SHIT. That is the worst constructed amp I've seen in my life. You sound like a Fender salesman! The amp is nearly impossible to service, and hence, will be nearly "disposable" when something goes wrong. To fix a problem, the amount of time required, and resulting hourly labor charges will be staggering. So much so, that in some cases it will be cheaper just to get a new amp. Add to that, how the hell do you optimize the bias on the output tubes? There's no adjustment, and changing resistors is nearly impossible because of the above mentioned problems. This amp will certainly meet Fender's goal for having a finite lifespan. Unlike the original Tweed and Blackface (and Silverface) amps that are still going strong today, it is highly unlikely that the new Super will live to see it's 40th birthday. The new Super, and all of it's brothers, are simply crap. Regards. Fender brownface topology From [email protected] Sat Oct 7 21:13:16 CDT 1995 Article: 4233 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newsfeed.internetmci.com!news.sprintlink.net!in1.uu.net!prodigy.com!usenet From: [email protected] (Joseph Pampel) Newsgroups: alt.guitar.amps Subject: Re: Info on Fender Pro Reverb wanted Date: 7 Oct 1995 04:01:46 GMT Organization: Prodigy Services Company 1-800-PRODIGY Lines: 58 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: inugap5.news.prodigy.com X-Newsreader: Version 1.2 [email protected] (Rennie Selkirk) wrote: 2. Certainly the above brown amps, and I believe the brown amps in general, > had lower plate voltages in the preamps, usually under 200 V, but with > 7025 phase inverters with fairly high plate voltages, up around 300 V > or more. In contrast the AA and AB763 amps of the same name had 200+ > voltages in the preamps and 12AT7 inverters, with voltages under 250. > > To an amateur like me, the higher preamp voltages in the black amps > spell something like cleaner and twangier. Maybe also richer. (Is that > the "spank" you're talking about?) Certainly not "browner!" > The brown schematics show lower plate volts on the pre-amp, but in practice (and esp with 120V coming out of our modern sokets) the pre-amps are hit with 200+ volts at the plate. The Phase inverter is always the highest pre-amp plate voltage becuase you want the largest voltage swing to drive the output tubes. The bias was running about -52 or so back then, which means that a 104V p-p signal would drive for full power (assuming everything else could keep up..) The PI would have more than 300V on the plates, but it must be remembered that the cathode is biased up to about 40V on the Brown amps, so the true plate volts are 40V (or so) lower than they appear when read at the plate. All else equal, higher voltages sound brighter and punchier. The Brown amps actually run about the same voltages (in general) as the BF amps.. The output plates are at 460VDC quiesent. One major difference I've noticed in goofing around with amps is that the brown amps have much lower gain pre-amps in general (check the split plate loads in the Vibroverb and 6G12-A Concert for example..) and then have a higher gain phase inverter to pick up the gain in the power amp. (using a 6.8K "tail" resistor where the BF amps are running 27K or so, much lower gain.) > Don't know what the difference the 12AT7 design makes, though I know > that the sound of my black Tremolux gets somewhat muddier when I replace > the 12AT7 with a 12AX7. > The 12AT7 was subbed for the 7025 for its lower gain, lower rp and its ability to deliver power to drive the outputs. When the output grids draw current (as grid potential approaches zero) you need to provide power from the driver stage to keep the waveform together. That's also part of what those series grid resistors are about. They are for stopping osc, but also they develop extra bias when the output tubes draw rid current. In Hiwatt circuits, they use a 10K?(20K? I forget..) in this position to help keep things loud and clean. Joe P. Fender coupling caps From [email protected] Wed Jan 10 11:09:08 CST 1996 Article: 5062 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!news.bluesky.net!solaris.cc.vt.edu!newsfeed.internetmci.com!swrinde!elroy.jpl.nasa.gov!ames!onramp.arc.nasa.gov!telsci.arc.nasa.gov!selkirk From: [email protected] (Rennie Selkirk) Newsgroups: rec.audio.tubes Subject: Fender coupling cap values Date: 9 Jan 1996 20:31:35 GMT Organization: NASA-Ames Research Center Lines: 31 Message-ID: <[email protected]> NNTP-Posting-Host: telsci.arc.nasa.gov I have noticed in comparing the schematics of this and the two other "first-generation" piggyback blackface non-Bassman amps (i.e. the Tremolux, Bandmaster and Showman) to their comparable combos (the Vibrolux and Vibrolux Reverb amps, the Pro Reverb and Twin Reverb, respectively), that Leo & co. chose 500 pf caps to couple the preamp to the phase inverter on the piggybacks and 1000 pf (.001 uf) for the combos. (Compare for example the AB763 Tremolux to the AB763 Vibrolux. They're identical except for this cap and the size of the phase inverter ground resistor which is 100 ohms for the 4-ohm load Tremolux and 47 ohms for the 8-ohm load Vibrolux combo.) Any guesses on the design rationale for this? Mine would be that the Leo & co. thought that the smaller cap would offset 'flabbiness' due to the increased bass response of the closed-back cabs relative to the open-back combos. I have tried both cap sizes in my Tremolux. It's my impression that the differences aren't that great. The bottom end is decidedly flabby in both cases, forcing me to back off on the bass more than I'd like in many situations. I think I hear another effect of the smaller cap, however, and that is to reduce the dynamics of the amp. The sound is tighter and little less mushy with the smaller cap, but some of the sparkle seems to go with it. A smaller hole to push the music through so to speak. Anybody care to comment on this or the issue of coupling cap sizes in general? Thanks, Rennie From [email protected] Wed Jan 10 11:09:16 CST 1996 Article: 5063 of rec.audio.tubes Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!newsfeed.internetmci.com!gatech!willis.cis.uab.edu!ddsw1!news.mcs.net!van-bc!news.mindlink.net!news From: [email protected] (EAL) Newsgroups: rec.audio.tubes Subject: Anyone know what happened to MagnaQuest? Date: Tue, 09 Jan 1996 22:16:27 GMT Organization: MIND LINK! - British Columbia, Canada Lines: 6 Message-ID: <[email protected]> NNTP-Posting-Host: line141.nwm.mindlink.net X-Newsreader: Forte Free Agent 1.0.82 Tried phoning them for the past 3 weeks... Regards, Ed. Fender decrease reverb mix From ice@snake Wed Apr 26 16:01:57 CDT 1995 Article: 48995 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!gatech!bloombeacon.mit.edu!boulder!ice From: ice@snake (John Mastrangelo) Newsgroups: rec.music.makers.guitar Subject: Re: 10pf cap in reverb mix circuit Date: 26 Apr 1995 15:09:41 GMT Organization: University of Colorado at Boulder Lines: 82 Distribution: inet Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: snake.colorado.edu In a previous article George Kaschner asks how he can reduce the amount of reverb in his mix and asks whether changing the 3.3 M resistor would be appropriate. In the interest of time, I'm going to make this brief. If it unclear, let me know and I will explain further. There are at least 10 ways to achieve this, but this approach is the simplest to implement, is the most effective, easist to analyze, couldn't be much cheaper (2 resistors) and most importantly will not affect any other function of the amp. Here we go: In most (if not all) Fender amps w/ reverb there is a multiple stage voltage divider which controls the dry gain of the reverb channel and the amount of reverb in the mix. This VD consists of the 3.3M/10pF pair and the 470k/220k pair connected to the center tap of the reverb mix control and the grid of the reverb recovery triode. Lets look at the reverb level first. The ratio 220k/(220k + 470k) controls the max amount of reverb available. Changing the ratio of these two resistors will control the max amount of reverb in the mix. George mentioned wanting to mod his reverb circuit such that on "10" it equalled the stock control on "3". Since the reverb mix control is linear, "3" corresponds to 30% of "10" which indicates that his resistor ratio above (220k/690k) = .32 should be reduced to .32*.3 = .095. Second is the gain of the reverb channel. Here the 3.3M/10pF pair and the *parallel* combination of the 220k/470k pair form a voltage divider which controls the gain of the dry reverb channel signal. The parallel combination of the 220k/470k pair is approx 150k ( the pot resistance is neg.) Ignoring the effect of the 10pF cap yields: 150k/(3.3M + 150k) = .043 = 1/23. So the reverb dry signal is being attenuated by a factor of 23. That is why the reverb channel has only slightly more gain than the Normal. Bottom line: * Decrease the ratio of the reverb signal VD from .32 to .095 * Maintain the parallel resistance of 150k from these two resistors. Bottom bottom line: * Replace the 470k resistor connected to the center tap of the reverb control with 1.5M. * Replace the 220k resistor with 180k. Then: Reverb divider ratio = 180k/(180 + 1500)k = .11 Parallel combination = 1/( 1/180k + 1/1500k) = 160k Which is plently close for what we are doing here. There are a lot of other effects that are connected to this discussion and I'd like to address them all, but I don't have the time or the desire to write a book. However, I'm happy to answer any questions that may arise from this article. John Mastrangelo Osprey Amplification Fender diodes From [email protected] Wed Apr 26 15:51:23 CDT 1995 Article: 1003 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news.nic.surfnet.nl!ecnits.ecn.nl!ecnfac.ecn.nl!bernards From: [email protected] (Marcel A. Bernards) Newsgroups: alt.guitar.amps Subject: Re: Old Fender diodes Date: 26 Apr 1995 08:05:39 GMT Organization: ECN - The Netherlands Energy Research Foundation Lines: 71 Distribution: world Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: ecnfac.ecn.nl In article <[email protected]>, [email protected] (XYZ) writes: >Does anyone know the origin or specifications of the bullet-shaped >solid-state diodes used in the the early (1960) Fender amps? >The first generation circuit shows three of the diodes in series >on each side of the AC secondary. When replacing these with new, >high voltage diodes (IN4007), is it necessary to have three in >series, too? >Thanks, >Ted a 1n4007 has a 1000 Volt reverse voltage capability , but they are if the voltage on the Caps is about +500 volt and the transformer voltage sine wave goes to negative, the overall voltage is about 1000 volt over the diodes The Fender has a dual coil transformer with a tap, an inheritance from the tube diode era. that's why you got that much voltage over the diodes. So it could be done with one diode, but with very little margin left So you need at least 2 in series, but they are dirt cheap, so it's hardly an issue to discuss what's better. 2 or 3 in series ? Hell, I buy them in packs of 25 pieces at my local shop. Newer amps have a single coil transformer and a Graetz style rectifier with 4 diodes. They cannot be used in those older fenders, because it needs a rewiring of the tranformer coil (parallel instead of in series) because the windings needs to supply juice for both sine halfs. It may be possible to split the coil tap in a fender transformer, but I'm not sure, and it's probably not worth the trouble. Small ascii drawings to explain: D1 D2 D3 +--->|->|->|---+ +500V #L| +---| 0V mass | Old style fender #L| +--->|->|->|---+ D4 D5 D6 +-+-+-->|------+ +500V |||| | | +--|<--+ | # # | | Modern style rectifier. | | +--|<--+0V | |||| +-+-+-->|------+ So you need at least 2 in series, but they are dirt cheap, so it's hardly an issue to discuss what's better. 2 or 3 in series ? Hell, I buy them in packs of 25 pieces at my local shop. Happy soldering [email protected] +---+ FTP.ECN.NL:/pub/DigiTech-Gear| Marcel A. Bernards +---------------=-=-=-=-=-+ | DigiTech Effects Archive&Mailinglist maintainer [ RP-1 [_____] + + -- Q Q ]| Also UNIX & Net SysAdmin @ ECN.NL +-------------------------+ | Netherlands Energy Research Foundation | |_| |_| |_| |_| |_| |_| | | P.O. Box 1, 1755 ZG Petten +-------------------------+ | (+31 /0)2246 4579 Fax: (+31 /0)2246 1864 | |_| |_| |_| |_| |_| |_| | | +-------------------------+ +-------"Do it all on the floor" subscribe: [email protected] subscribe RP-1-L Fender neg feedback From [email protected] Fri Jul 21 13:47:37 CDT 1995 Article: 58531 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!swrinde!elroy.jpl.nasa.gov!lllwinken.llnl.gov!ames!onramp.arc.nasa.gov!telsci.arc.nasa.gov!selkirk From: [email protected] (Rennie Selkirk) Newsgroups: rec.music.makers.guitar Subject: Re: Bassman Mod. Question Date: 20 Jul 1995 22:21:23 GMT Organization: NASA-Ames Research Center Lines: 34 Distribution: usa Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: telsci.arc.nasa.gov Dave Cigna wrote in response to the suggestion of removing the negative feedback in the output stage of a '67 Bassman: > >Put that feedback network back. It's true that these >were the "experimental" years for Fender, so they might >have tried something a little different, but as far >as I know, every Bassman ever made incorporated some >kind of negative feedback. Either put it back the way >it was or install a blackface style feedback curcuit. I assume we're talking about the standard black/silverface 820 ohm resistor between the speakers and the input of the phase inverter. I recently went BACK to the original setup on my blackface (64 Tremolux) from an 1800 ohm resistor which I had substituted a few months ago when I was in search of "crunch". As you'd expect the higher value feedback resistor audibly increased the distortion in the amp by reducing the negative feedback signal, and I think gave me a bit more dynamics, but I wouldn't describe the effect as -pleasingly- increased crunch. I would rather call it increased sludge! With the return to the stock setup, I find I like the increased fidelity, especially at higher volumes. Keep in mind I'm driving this amp with a guitar/pickup setup (archtop with 490s) that you might say is the electric guitar equivalent of very rich chocolate cake. I guess the moral of the story is that Leo and his people knew what they were doing back in 1963 when they introduced the blackface amps with all that negative feedback, though it may be that the feedback's benefits vary from one amp model to the next, since they put the 820 ohm resistor in all the 6L6 blackfaces without regard to power. I don't have the experience to say one way or another. However, I can say that for my Tremolux, it's definitely beneficial. HJBoogie From Fri Jul 21 13:47:51 CDT 1995 Article: 58616 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!news.cac.psu.edu!news.math.psu.edu!ra.nrl.navy.mil!psl1.nrl.navy.mil!user From: () Newsgroups: rec.music.makers.guitar Subject: Re: Bassman Mod. Question Followup-To: rec.music.makers.guitar Date: 21 Jul 1995 15:22:01 GMT Organization: Naval Research Laboratory Lines: 12 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: psl1.nrl.navy.mil In article <[email protected]>, [email protected] (Rennie Selkirk) wrote: > > Dave Cigna wrote in response to the suggestion of removing the negative > feedback in the output stage of a '67 Bassman: >> I've modded my Silver Face Super Reverb so the feedback resistor can be switched in and out of circuit. I used the "bright" switch on the normal channel for this. Best of both worlds. _Paul Fender replacement parts From [email protected] Fri May 5 14:32:28 CDT 1995 Article: 1104 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!gatech!bloom-beacon.mit.edu!panix!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: Amp Corners for Fender? Date: 5 May 1995 06:54:23 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 9 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com Regarding replacement Fender parts: Fender refers users to (I believe it is...) Smart Parts (Chicago) 708-427-0053. They may or may not have a clue . Mark Garvin From [email protected] Fri May 5 14:32:41 CDT 1995 Article: 1107 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!gatech!bloom-beacon.mit.edu!panix!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps Subject: Re: Amp Corners for Fender? Date: 5 May 1995 10:36:09 -0400 Organization: Public Access Internet & UNIX Lines: 13 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix3.panix.com Charlie Metcalf wrote: >So what's the best source for replacement amp corners that will look like >the originals, and the screw holes will match-up? Fenton (Tel: 1-800-336-8662). -Len Moskowitz Core Sound [email protected] Fender speaker recs From [email protected] Wed Oct 4 12:11:00 CDT 1995 Article: 4160 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!sgigate.sgi.com!sdd.hp.com!usc!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Vintage Fender Speaker Questions Date: 4 Oct 1995 02:34:19 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 19 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com Depending on how "heavy" your wallet is, you have several choices for speakers. In the 12" category, if you want vintage tone with a big full low end, you'll be hard pressed to beat a pair of old Jensen P12N alnicos. They're expensive, but they sound great. If you can't afford that, look into the Celestion Vintage 30s. For 10" speakers, there's the Celestion Vintage 10. The Mojo alnico 10s are a little lightweight for this amp, since they're P10R repros. I don't think the really excellent old Jensen P10Qs would live in this amp, they'd blow. The Jensen ceramics may be an option. Maybe you can find a set of C10Ns. A Pro Reverb with an 8 ohm transformer???? Not that I've ever seen. If your transformer has part number 022848, it's a 4 ohm transformer. Make sure your tech knows what the hell he's doing. Hope this helps. Regards. Fender tone circuit boost From [email protected] Wed Mar 27 13:28:41 CST 1996 Article: 12024 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!usc!howland.reston.ans.net!newsfeed.internetmci.com!in2.uu.net!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: Deluxe Reverb, tech questions Date: 27 Mar 1996 01:26:54 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 24 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: newsbf02.mail.aol.com In article <[email protected]>, [email protected] (LarrySB) writes: > >I plan to ditch the volume boost switch circuit, and re-wire the switch as >a bright switch. I'm thinking of setting it so that "in" switches bright >on, "pull" switches it out. > > Here is no brainer switchable gain boost that may be worth experimenting with. Simply disconnect the midrange lead that goes to ground and connect it to your switch wired to ground. When it is disconnected, so is your tone stack. No signal goes to ground. You end up with a very nice boost, but your tone controls do nothing when the switch is on/off. This is also a good way to get some mileage of an unused bright switch on other Fender models. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. From [email protected] Thu Mar 28 13:13:07 CST 1996 Article: 12074 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!usc!elroy.jpl.nasa.gov!news.msfc.nasa.gov!sgigate.sgi.com!imci3!imci2!news.internetMCI.com!newsfeed.internetmci.com!howland.reston.ans.net!newse2a.gnn.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: Deluxe Reverb, tech questions Date: 28 Mar 1996 02:05:44 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 12 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> In article <[email protected]>, [email protected] (Cogito1271) writes: >Disconnecting the ground to the tone stack is how Mesa used to wire their >Gain Boost switch on the original amps. Works pretty well, too. I sniped that trick out of a West amplifier, it was the "LOUD" switch. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. Fender vibrato pot From [email protected] Wed Oct 4 12:07:12 CDT 1995 Article: 4161 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uunet!in2.uu.net!umcc.umich.edu!news.eecs.umich.edu!panix!not-formail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: vibrolux-to-vibroverb tremelo mod Date: 4 Oct 1995 02:29:28 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 60 Message-ID: <[email protected]> References: NNTP-Posting-Host: panix2.panix.com In [email protected] (Al Lighton) writes: >The tremelo on my 71 vibrolux went out, and it isn't the tube. It's >.. >But I played a vibroverb reissue next to a vibrolux and I thought the >sound of the vibroverbs tremelo was much better. It was less choppy, >smoother overall. Plus I didn't notice it ticking all the time like my >vibrolux does. >The Weber book makes a big deal about the circuit in the first vibroverbs >modulating the power amp bias instead of grounding the phase inverter. >Weber also indicates that the grounding tremelo circuit is never >completely off, and sucks a little tone. I have the circuts for both >styles. Has anyone ever converted a stanadard blackface tremelo (i.e >super, Pro, vibrolux, twin etc) to the virbroverb style tremelo? Would >you recommend it? is Lead dress especially critical? Does it get rid of >the tick? Any recommendations appreciated. Tricky question, Al. Kinda labor-intensive, and I'm not the one to judge--I don't use tremolo. But I *can* answer: The lead dress will not be as critical as the present version. The tick comes from the neon light firing, so that would go away. Fender knocked a bit of gain out of the circuit with their LDR-neon vibrato. Not sure why they used a 50k pot, but it loads the previous tube stage down drastically. Chances are that your neon light popped or associated wiring broke. So probably no major repair. You could try using a higher value pot if you really need the gain from that channel. Make sure it's a reverse audio taper (hard to find). Values higher than 100k to 250k will have dead space in the control's rotation. Even the 250k will take a bit to get started but it won't load down the tube quite as much as a 100k. The dynamic impedance (looking backward into the plate circuit) is probably around 70k or so, depending on how the tube is biased. So 100k will still lose a couple db. Weber tends to equate volume/level with tone. The psychological effect is similar, but can usually be had by cranking the volume control. You'll notice that more volume it *seems* to make the amp sound fuller and richer. Weber consistently refers to this as tone. In other words, you can compensate for the 50k-ra pot loading losses by cranking the volume a bit. Loading loss is usually slightly asymmetrical, so it sometimes creates a bit of even- harmonic distortion. The nice kind. In this case it won't be extreme. About whether to do the bias-mod: use your own judgement. Be careful though. Messing with the bias can toast the output tubes which can then take the output transformer down with them. No loose wires. And test thoroughly with the output tubes pulled. But you knew this, right? Regards, Mark Garvin Footswitch specs From [email protected] Sat Dec 28 09:37:00 CST 1996 Article: 32314 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!feed1.news.erols.com!news.idt.net!nntp.farm.idt.net!news From: Paul Cassone Newsgroups: alt.guitar.amps Subject: Re: Footswitch?? Date: Sat, 28 Dec 1996 02:15:02 -0800 Organization: IDT Lines: 20 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: ppp-32.ts-4.nyc.idt.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.01 (Win16; I) James, Parts: Two spst pushbutton switches Two RCA jacks Length of shielded cable with two hot wires Box Rubber grommet for where the wire leaves the box The vibrato switch merely shorts hot to ground - the ground of the plus is not even connected The reverb switch uses a shielded cable (the shield and one hot), and hitting the switch clses the circuit so that shield and hot are connected. Good luck Paul Grid Blocking From [email protected] Tue Jul 22 12:01:47 CDT 1997 Article: 57134 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer.sprintlink.net!news.sprintlink.net!Sprint!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!mindspring!news.mindspring.com!usenet From: Randall Aiken Newsgroups: alt.guitar.amps Subject: Re: bass notes "farting out" on BF Super Reverb Date: Tue, 22 Jul 1997 01:57:54 -0400 Organization: MindSpring Enterprises Lines: 189 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: user-37kbv3a.dialup.mindspring.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Server-Date: 22 Jul 1997 06:01:04 GMT X-Mailer: Mozilla 3.0Gold (Win95; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:57134 J wrote: > > In <[email protected]> [email protected] writes: >> > >I've got a '65 super reverb, with 4 new Weber VST p10r's. The amp > >sounds incredible, as most BF SR's do. However, I was playing at an > >outdoor jam the other day, and trying to get some good volume out of > >the amp. It exhibited the usual (in my experience) Fender symptoms: > >high volume bass-farting. >> > > The source of your bass flatulence is probably grid conduction > in the output tubes. I have the same problem with my 69 Super. > For a long time I thought it was the stock CTS speakers bottoming > out but a fellow on this NG (Mark Garvin) suggested it could be > grid conduction. I took the chassis out and set it up on my > bench with speaker and guitar plugged in and an AC coupled scope > on one of the power tube grids. When I struck a chord on the > bass strings with the volume on 8 I could see the signal from the > phase inverter clip just at the onset of farting. Whats happening > here is when the PI signal goes more positive that the 6L6 cathode > the grid starts to conduct and clamps the signal at the cathode > voltage. Yep, our wonderful old Fender has diode clipping at this > point. Let me note that everything in the amp circuit is "correct". > I made the SF>BF conversion but it did not cure this problem. I'm > not sure what to do about it other than not playing that loud. > Anyone have any suggestions? > > Joe Oh, boy! My favorite subject to harp on has reared it's head once again...(no, not cathode followers, although I'll work those in later on...!). Your amp is likely suffering from what is commonly known as "blocking" (not the RDH4 definition of blocking, but the more esoteric Crowhurst definition). Blocking occurs when, as you mentioned above, the output tube grids are driven to the point of conduction. Since the previous stage is a relatively high impedance source, and, to make matters worse, is AC-coupled, it cannot maintain enough drive to the output tube grids to maintain the signal once the output tube goes into grid conduction. The grid of a tube normally presents a very high impedance load to the driving source when it is biased in the negative region. When the tube grid bias voltage nears zero, or goes positive with respect to the cathode, its input impedance drops drastically, and it starts drawing current from the source. It behaves similarly to a forward biased diode at that point. If the driving source is capable of providing this extra current that is needed, the tube will continue to amplify normally and put out additional power. This is commonly known as class AB2 operation, where the 2 suffix indicates grid current being drawn during a portion of the cycle, as opposed to class AB1 operation where no grid current is drawn. Now, the problem with your standard resistance-capacitance coupled amplifier stage is that the onset of grid current makes this forward biased diode out of your previously high-impedance grid circuit. This results not in diode clipping, as mentioned above, but rather diode _clamping_, which is the cause of both the transient distortion, and an increase in another type of distortion known as crossover distortion. What happens is, the forward biased diode clamps the tops of the grid waveform to a relatively fixed point. Since the previous stage is AC coupled to the grid, the tops are fixed at the clamp point and the entire waveform then shifts downward as gain is increased, pushing the amp more into class B operation, with a resultant increase in crossover distortion. Since each tube in a push-pull class AB or class B pair amplifies only part of the waveform, the two halves are summed back together in the output transformer secondary to produce the full waveform. If the amp is pushed farther into class B operation, the resulant waveform will have it's center "cored out", producing a dead zone, or flat spot, at the zero crossing of the waveform. This occurs because the center portion of each half has been pushed down into the cutoff portion of the tube's operation. This is known as crossover distortion, and too much of it can sound really bad. In addition to an increase in crossover distortion, if the time constant of the AC coupling is large enough, and the transient waveform is of low enough frequency, a transient distortion known as blocking occurs. This happens when the transient signal quickly pushes the clamped grid waveform down far into the cutoff region, and there is a finite time that is required for the grid waveform to recover and float back up to the correct bias point once the transient signal is removed. Until the bias comes back to the correct point, the output stage is effectively cut off for a major portion of the signal. This results in a choppy, "farting" sounding distortion. Fender amps are particulary susceptible to this because of the large values of coupling capacitors on the grids of the power tubes (0.1uF). Blackfacing your Super Reverb can actually make the problem worse, because you change the grid bias feed resistors from 100K to 220K, which increases the time constant of the AC coupling to the output tube grids. You will note that most Marshalls use 0.022uF coupling capacitors and 100K resistors, which gives a much faster time constant. In addition, the preamp stages have a much more rolled off low frequency response. This is why they sound tighter when played wide open. Negative feedback can exacerbate (I've always wanted to use that word! ) this problem. When the output tube goes into cutoff, the negative feedback loop opens up, and the gain of the phase inverter stage increases by the amount of degenerative feedback that was formerly present. This increase in gain pushes the amp even farther into cutoff. What can be done to fix this problem? I only know of a few solutions, and any of them will change the sound of your amp to a certain degree. Fenders sound the way they do because of the design values, and anything you do to change them will take away from some of that characteristic tone. Having said that, here are the solutions: First, reduce the value of the coupling capacitors. Try progressively lower values until you find one that reduces the problem, but doesn't rob you of too much low end. Second, reduce the value of the grid bias feed resistors. This has the unfortunate side effect of attenuating the gain of the signal from the phase inverter, which may or may not be that noticeable. Third, increase the size of the so-called "grid stopper" resistor, which is usually a 1.5K - 5.6K resistor in series with the output tube grids, and is usually soldered directly to the grid pin as a parasitic oscillation prevention measure. Increasing the size of this resistor will limit the amount of grid current that can be drawn and reduce the clamping effect quite a bit. This modification has the unfortunate side effect of rolling off the high frequency content of the amp. Depending upon the type of output tube, you can probably go up to around 50K 100K max before the high frequency loss becomes too noticable. (Remember, most guitar speakers don't do too much above 4KHz anyway). Another potential problem with this method is that the output tube is rated for a maximum grid circuit resistance, beyond which it will become unstable due to changes in grid voltage caused by the voltage drop across the grid resistor from small grid currents. This value is published by the manufacturer typically as two values, one for fixed-bias operation and a higher value for cathode bias operation, since it is self-correcting to a certain extent. The sum of the bias feed resistor and the grid stopper resistor should not exceed the maximum stated value for the grid number 1 circuit resistance. Fourth, add a DC-coupled cathode follower between the phase inverter and the grid of the output tubes, with the cathode follower cathode resistor returned to a high negative voltage, and the grid bias applied to the grid of the cathode follower. This effectively isolates the output tube grid circuit from the phase inverter and its associated AC coupling, and provides a very low-impedance source for the output stage. This will prevent the output stage from going into grid clamp, and will eliminate the long time constant of the AC coupling. This method has the unfortunate side effect of requiring an extra tube and completely ruining the value of your vintage amp, so it is best used only on new designs. :) Fifth, limit the signal level to the output stage at full volume by adding either a resistor across the phase inverter outputs (after the coupling caps) or by adding series resistance on each side between the coupling caps and the grid bias resistors. Adjust the attenuation so the output stage starts to clip only after the phase inverter starts to clip. If you can prevent the output stage from going too far into grid clamp, you can minimize the problem. Sixth, reduce the amount of negative feedback used, or remove the negative feedback loop entirely. Generally you will have too much gain in the output stage once you remove the feedback loop, so you will probably want to reduce the signal level as indicated in the fifth method outlined above. This method has the unfortunate effect of rendering any existing presence control inoperable. If you must have presence, add a "treble cut" pot across the phase inverter output as in the VOX AC30, and increase the treble in a previous stage to give you some extra treble to work with. Seventh, look for the problem in the preamp stages. Blocking can (and does) occur just as bad on RC-coupled preamp stages that are overdriven. The solution is similar. Add large value series grid resistors (100K 470K), reduce coupling capacitor values to the minimum required for the desired low frequency response, or add a diode clipper bounding circuit to prevent the grid from being driven too far. That's it. If you aren't completely bored or confused by now, and would like to read further about this, do a Deja News search under my name on the old non-current newsgroup database and you'll likely run across some articles I wrote a year or two ago on this very subject. Hope this helps, Randall Aiken [email protected] Homebrew Vibroverb From [email protected] Thu Jan 19 11:17:08 CST 1995 Article: 37642 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!swiss.ans.net!newstf01.news.aol.com!not-formail From: [email protected] (Tremolux) Newsgroups: rec.music.makers.guitar Subject: Re: Help:'69 Fender Super Reverb Date: 18 Jan 1995 19:40:45 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 22 Sender: [email protected] Message-ID: <[email protected]> References: Reply-To: [email protected] (Tremolux) Fenders are not designed to be "distortion" amps, and to get one of the old ones to distort, you really gotta crank it up. The Blackface mod basically changes some resistor values in the phase inverter to give the later model amps a bit more gain there like the older ones had. It also removes some capacitors that kill harmonics, giving the amp much better transient response and high-end. The AB763 is the Blackface era circuit. The AA586 (I think) was the first silverface bastardization that come out in 1968, shortly followed by the AA1069, which un-did a few of the changes introduced by the 568. I think there's also an AA270, but I'm not positive. I have an AA1069 Bandmaster Reverb head that I've converted to the 763 circuit, and it sounds noticibly better. That chassis now resides in a combo cabinet with a 15" JBL (I changed the output transformer as well). Can you dig a "homebrew" Blackface Vibroverb at a fraction of the cost of a real one? Shades of Stevie Ray Damn near everyone I know who has a silverface Fender has had the mod done. Regards. Invert normal channel From [email protected] Mon Oct 13 14:57:34 CDT 1997 Article: 67024 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!newspeer.sprintlink.net!news.sprintlink.net!Sprint!news.maxwell.syr.edu!cam-newshub1.bbnplanet.com!news.bbnplanet.com!panix!news.panix.com!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps Subject: Re: Pro Reverb/Jim Kelley/GT Soul-O 45 Date: 13 Oct 1997 11:49:16 -0400 Organization: Panix Lines: 27 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix3.panix.com X-Newsposter: trn 4.0-test55 (26 Feb 97) Xref: geraldo.cc.utexas.edu alt.guitar.amps:67024 Richard P Towne wrote: > Three subjects: 1. If you plug two input into separate channels of a > blackface Pro Reverb are they out of phase? Yes, but an MXR Dynacomp in-line to the second channel will invert the phase. With an A/B/Y box that gives the Pro Reverb (and most older blackface amps) very flexible tone. I go into the ABY with my guitar and send the straight signal to the Vibrato channel with the tone controls set a little bright. The compressed and slightly boosted signal goes to the "normal" channel with the tone set a little dark. The contrast is very nice and the boosted/compressed tone is very nice. > Does that apply to all two channel blackface Fender reverb amps? I think so but I'd have to check the schematics on all of 'em to be sure. -Len Moskowitz Core Sound WWW site: http://www.panix.com/~moskowit [email protected] Knob Changes From [email protected] Sat Aug 8 20:47:18 CDT 1998 Article: 120589 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!Supernews60!supernews.com!Supernews69!notfor-mail From: "profrets" Newsgroups: alt.guitar.amps Subject: Re: BF Super Reverb Qs Date: Sat, 8 Aug 1998 18:24:54 -0400 Organization: http://www.supernews.com, The World's Usenet: Discussions Start Here Lines: 19 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: 207.141.129.93 X-Trace: 902616442 JPTWPMLIW815DCF8DC usenet57.supernews.com X-Complaints-To: [email protected] X-Newsreader: Microsoft Outlook Express 4.72.2106.4 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.2106.4 Xref: geraldo.cc.utexas.edu alt.guitar.amps:120589 kevmin wrote in message <[email protected]>... >The original knobs will have a smaller circle on the top of the "8" and a >bigger circle on the bottom. The 70's knobs had the same size on the top >and bottom of the "8". I haven't been able to notice any tonal difference >between the different knobs. Maybe Eric Johnson could? >Best of Look, sounds like a great buy. Don't put Kendrick speakers in it. >I did and it doesn't sound like a blackface anymore. Too distorted. Just >my 2 cents. > >Kev Also, the blackface knobs have the screw under the "10". '68 and later, the screw is under the "1". I have seen reissue knobs recently where the screw is under the "10" again, but not very many. [email protected] More Pro Reverb From [email protected] Sun Oct 1 10:59:30 CDT 1995 Article: 4064 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!in2.uu.net!panix!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps,rec.music.makers.guitar Subject: Re: Info on Fender Pro Reverb wanted Date: 29 Sep 1995 14:38:54 -0400 Organization: Panix Lines: 45 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: panix3.panix.com Xref: geraldo.cc.utexas.edu alt.guitar.amps:4064 rec.music.makers.guitar:65590 In article <[email protected]>, Jeff Olsen wrote: >I'm salivating over a blackface Pro reverb at the shop I work at now; >I've heard that many of the silverface amps are revertable to black spec >pretty easily, and that the Pro was one of the the less messed-with amps >anyway by CBS engineers. Most of the silverfaced Pro needn't be modified -- just the ones in '69 and early '70 with the 150 Ohm resistors in the cathode circuit. The later ones were reverted to the blackface specs with some useful improvements that make them even better than the '65 & '66 blackfaced and '66 - '68 silverfaced Pros (IMO). >Does it make sense to spring for the black one >(great shape, except the original "feet" were removed and replaced with >casters) for around 800 bucks, or get a silver and revert it? Anyone >done this particular conversion? That's a dealer price. You can get one privately for $650 to $750. If all you are after is tone, the '71 and later (until the master volume mods came in on the Fender line) sound great and are good values. I have a '71 for sale for $550 (or best offer) in excellent original shape; you can find them lower priced in lesser condition. The blackfaced amps have one interesting feature that the later ones don't: the baffle board is removeable. This allows you to easily substitute other speaker combinations. For example, I have plans to put a 15" JBL D-130 in mine to give me something akin to a Vibroverb. I'll be able to restore it to stock without any problem if I should care to. The silverfaced amps have a non-removeable baffle. >As an owner of a Blackface Deluxe Reverb that has appreciated about 200 >dollars over the last year and a half, I don't mind springing for the >black Pro, although I know it's not as collectable as the Deluxe. Boy, >does it sound good, though... They sure do and the tube rectifier has a lot to do with that. In my opinion, the Pro Reverb is best amp Fender ever made. -Len Moskowitz Core Sound [email protected] From [email protected] Sun Oct 1 10:59:56 CDT 1995 Article: 4097 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!agate!newsxfer.itd.umich.edu!news.eecs.umich.edu!panix!notfor-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps,rec.music.makers.guitar Subject: Re: Info on Fender Pro Reverb wanted Date: 1 Oct 1995 10:33:52 -0400 Organization: Panix Lines: 18 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: panix3.panix.com Xref: geraldo.cc.utexas.edu alt.guitar.amps:4097 rec.music.makers.guitar:65716 I wrote: >The blackfaced amps have one interesting feature that the later ones >don't: the baffle board is removeable. This allows you to easily >substitute other speaker combinations. For example, I have plans to put >a 15" JBL D-130 in mine to give me something akin to a Vibroverb. I'll >be able to restore it to stock without any problem if I should care to. >The silverfaced amps have a non-removeable baffle. I should have qualified this. The silverfaced amps from 1972 onward have the non-removable baffle boards. All the blackfaced ones and the silverfaced ones from '66 to '71 have removable baffles. -Len Moskowitz Core Sound [email protected] Narrow Deluxe Chassis Subject: Re: Tweed Deluxe chassis dimensions Date: 27 Apr 1997 00:00:00 GMT From: Lee MacMillan Organization: AT&T WorldNet Services Newsgroups: alt.guitar.amps 6L6 wrote: > > > > >>> Can someone give me the dimensions of a Fender tweed Deluxe chassis? >>> > > > >>The 1955 narrow panel deluxes were 16 1/2 x 18 x 8 3/4. In 1956 they > > > >>went to 16 3/4 x 20 x 9 1/2. See the Teagle/Sprung book at 44. >>> > > > >Those sound like the cabinet dimensions, not the chassis dimensions > > oops . . . Chassis dims are 14 7/16 x 4 1/16 x 2 1/16 for the 5E3 (thanks to 50D for the info.) Lee -Indiana's best equipped hack guitar player. Subject: Re: Tweed Deluxe chassis dimensions Date: 26 Apr 1997 00:00:00 GMT From: Lee MacMillan Organization: AT&T WorldNet Services To: Karl LaFong Newsgroups: alt.guitar.amps Karl LaFong wrote: > > [email protected] (Robert Fries) wrote: > > >6L6 wrote: > > >>Lee MacMillan wrote: > >>> > >>> Can someone give me the dimensions of a Fender tweed Deluxe chassis? > > >>The 1955 narrow panel deluxes were 16 1/2 x 18 x 8 3/4. In 1956 they > >>went to 16 3/4 x 20 x 9 1/2. See the Teagle/Sprung book at 44. > > >Those sound like the cabinet dimensions, not the chassis dimensions. > > >RF > > A tweed deluxe (narrow panel) has mounting centers of 13 1/2". Chassis > itself is 15" long I think. Thanks. That helps. Lee -Indiana's best equipped hack guitar player. No 5R4s From [email protected] Sun Jan 5 22:04:03 CST 1997 Article: 33285 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!cam-newshub1.bbnplanet.com!news.bbnplanet.com!cpk-newshub1.bbnplanet.com!portc02.blue.aol.com!newstf02.news.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: 5R4 vs. 5AR4/GZ34 Date: 6 Jan 1997 02:01:28 GMT Organization: AOL http://www.aol.com Lines: 24 Message-ID: <[email protected]> References: NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] >>>My '68 Super Reverb came with a Sylvania 5R4 rectifier tube instead of the specified 5AR4/GZ34. >>>What's the difference between these tubes? Quite a bit. The 5R4 is built somewhat like a 5U4, EXCEPT the 5R4 is designed to operate at higher voltages and lower load currents. The 5R4 does NOT belong in a Super Reverb. You don't need the higher voltage capability, but you do need higher current capability. The 5AR4 used indirectly heated cathodes and can deliver more current than a 5R4, with significantly lower losses. The 5R4 was used in transmitters mostly, for powering 6146, 807 and 1625 type transmitting tubes at 600 to 700 volts on the plates. >>>Is it OK to use a 5R4 instead of the 5AR4? If so how will it affect the sound/performance of the amp? I would recommend against it, for the above listed reasons, you need a higher current rectifier. With a 5R4 in the Super, you'll have lots of envelope sag and lose a bit of power. Tremo. Normal Channel Delay From [email protected] Tue Apr 1 21:27:04 CST 1997 Article: 43868 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!newspeer.sprintlink.net!news.maxwell.syr.edu!newsfeed2.aimnet.com!news1.aplatform.com!viper.inow.com!notfor-mail From: "Bean" Newsgroups: alt.guitar.amps Subject: Re: DR Mod question Date: 1 Apr 1997 20:01:58 GMT Organization: Preferred Company Lines: 11 Message-ID: <01bc3ed7$de684f40$d82958cf@Pbean> References: <[email protected]> NNTP-Posting-Host: du117.inow.com X-Newsreader: Microsoft Internet News 4.70.1157 Xref: geraldo.cc.utexas.edu alt.guitar.amps:43868 Jeff Ford wrote in article <[email protected]>... > I hate to think > of that normal channel just sitting there going to waste. An unrelated but neat use of that channel is to turn the tone and bass knobs all the down, and send the wet signal only from a digital delay to it while your unprocessed sound goes to the vibrato channel. Instant analog delay simulation! John PA 100 From [email protected] Sat Jun 7 08:18:12 CDT 1997 Article: 52292 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!newspeer.sprintlink.net!news-pull.sprintlink.net!news-ineast.sprintlink.net!news.sprintlink.net!Sprint!204.60.0.2!nntp.snet.net!news.snet.net!usenet From: Anwari Newsgroups: alt.guitar.amps Subject: Re: Fender P.A. 100??? Date: Fri, 06 Jun 1997 22:54:24 -0400 Organization: !!!mail me here!!! Lines: 12 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: nwhn02-sh8-port222.snet.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win95; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:52292 r_honez wrote: > > Hi all... > > Have any of you heard of, seen, etc., a Fender P.A. 100? It's a bizarre mutation of a Twin Reverb. A Dual Showma Reverb head on steroids? Anyway, it has the standard 100W versions of the Twin/Dual showman transformers 4 12AX7's, 2 12AT7's, 4 6L6's. The later verison, the PA 135 had the ultralinear transformer/no choke of the late Twins. Kap'n Pot Tapers From [email protected] Sat Feb 1 11:11:47 CST 1997 Article: 36732 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!www.nntp.primenet.com!nntp.primenet.com!mr.net!winternet.com!news.myna.com!n1tor.istar!tor.istar!east.istar!ott.istar!istar.net!n3ott.istar!news.quebectel.com!news From: "Claude Beaupré" Newsgroups: alt.guitar.amps Subject: Re: Tone pot tapers? Date: 1 Feb 1997 03:36:51 GMT Organization: GlobeTrotter Lines: 36 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ts1-26.f119.quebectel.com X-Newsreader: Microsoft Internet News 4.70.1155 Dean Hazelwanter a écrit dans l'article <[email protected]>... > I am in the process of building a multi-channel tube guitar preamp, > and have a question about tone circuit pots. What taper of pot > should be used for both Marshall and Fender 'classic' tone circuits? > > Marshall Fender > Treble 250K 250K > Mid 25K 10K > Bass 1M 250K > > Thanks in advance for any and all responses! > > I took notes, from amps I owned, fixed, modified, or built. I don't know if they are the rules or the exceptions Marshall Fender BF Fender SF Treble 250K-50% 250K-30% 250K-30% Mid 25K-50% 10K-10% 10K-10% Bass 1M-30% 250K-10% 250K-30% Legend: "%" = resistance readings between ccw and center terminals, wiper set at 50% mecanical rotation. 50% = Linear Taper. (LIN, or B) 10% = Audio, or Log Taper. (LOG, or AUD) 30% = Audio, or Log Taper. (LOG, or AUD 2-35) Claude Princeton Adjustable Bias From [email protected] Sun Feb 7 16:15:28 CST 1999 Article: 157492 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer1.sprintlink.net!-program!newspeer.gip.net!news.gsl.net!gip.net!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: Please Help with bias on Princeton Reverb Date: 7 Feb 1999 06:50:38 GMT Organization: Netcom Lines: 80 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: den-co59-17.ix.netcom.com X-NETCOM-Date: Sun Feb 07 12:50:38 AM CST 1999 Xref: geraldo.cc.utexas.edu alt.guitar.amps:157492 In <[email protected]> Paul Cassone writes: > >I have a '79 Princeton Reverb which needs a bias adjustment. The plate >current is 425, and the NOS 6V6's are drawing 32 milliamps. To avoid >having the tubes blow up, I know that I need to get the current draw >down to around 24 - 26 milliamps. This amp has no bias adjust pot, and >a resistor or two will need to be changed. I thought I knew which >resistor needed to be varied, and I used the method Weber suggests, of >putting a 250K pot across it but I must have put the pot across the >wrong resistor. The current draw didn't change and I blew up the pot. > >What I was supposed to do, according to Weber, was to monitor current >draw while I turned the pot until I got the current draw where I wanted >it. Then I was supposed to measure the value of the pot, find a >resistor of the same value, and then solder it across the resistor on >the board. > >Sounds logical to me, but I must first find the right resistor, right? > >So, any clues? Which resistor or resistors should be varied with this >amp to set bias? Is the Weber method a sound approach? Any other >methods you like better? > >Your advice and suggestions are much appreciated. > >Regards, > >Paul Lord Valve Speaketh: OK, Paul, forget all that bullshit you just wrote about and do it right this time. You have a resistor that is in parallel with the bias cap; one end is grounded, the other is connected to the negative lead of the cap. The lower the value of this resistor, the lower the bias voltage will be, and the more current the output tubes will draw. A higher value will give a higher bias voltage, and cause the tubes to draw less current. Here's what you need to do: unsolder the existing resistor and chuck it. Whatever value the resistor is now (let's say it's 33K, 'cause I can't remember and all my schematics are down at the shop) cut it in half and put it in series with a pot that's twice the new value. For a 33K resistor, rounding the values off to standard components, that gives us a 15K resistor and a 25K pot. In order to use the pot as a variable resistor (rather than a voltage divider, which is how pots are most often used) you'll need to tie the center lug to either of the outer ones. Now, you have a 2-terminal pot. Solder one lead of the new resistor (15K) to the ground point, where you removed one lead of the old resistor. Solder the remaining lead to one of the terminals on the pot. Solder the other terminal on the pot to the negative lead of the bias cap, from which you removed the other lead of the original resistor. You now have a variable bias supply, which you can tweak to your heart's content. BTW, use a trimpot, of the stand-up variety. The whole shebang will fit into the space where the old resistor was. This rig will give you a supply that has a voltage range of from somewhat lower than the stock resistor to somewhat higher. The reason that you don't use *just* a pot is this: if one end of the pot is grounded (which it would be if you didn't use the 15K series resistor) then the bias supply will go to zero if you turn the pot all the way down; that'll smoke the pot, and smoke the tubes, too, if you leave it that way for longer than 10 seconds or so. If you find that you still can't get enough negative voltage to set your idle current correctly, raise the value of the series resistor by 5 or 10 K. Lord Valve Visit my website: http://www.freeyellow.com/members2/lord-valve/ Good tube FAQ for newbies. Click the e-mail link and join my SPAM LIST; just put "SPAM ME" in the header and I'll sign you up. (If you only want a set of e-mail catalogs, put "CATS ONLY" in the header.) I specialize in top quality HAND-SELECTED NOS and current-production vacuum tubes for guitar and bass amps. Good prices, fast service. TONS of gear and parts in stock...let's DEAL! NOW ACCEPTING VISA, MASTERCARD, AND DISCOVER! "I got the chop...I'll never get popped." - Tower of Power Princeton Mods From [email protected] Sat Sep 21 20:08:24 CDT 1996 Article: 23170 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!news.sgi.com!news.msfc.nasa.gov!newsfeed.internetmci.com!newsxfer2.itd.umich.edu!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Simple Princeton mods? Date: 21 Sep 1996 19:07:36 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 28 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com Juicing up a Princeton? Forget any hacks that require major butcher jobs. Here's some simple reversable mods that still keep it looking and sounding like it's supposed to. 1. - You might replace the stock wimpy output transformer with one from a Deluxe, they're beefier. 2. - Consider replacing the stock speaker with one that's more efficient. Stick with the 10" to avoid a hack job, just get one that puts out more dBs of sound for a given input power. 3. - The stock phase inverter circuit is kind of lame. You can get major improvements by increasing the headroom. Do this by moving the supply connection for the phase inverter to the next higher tap on the power supply voltage divider. (Yeah, I've seen some that didn't have enough headroom to drive the 6V6s to saturation.) 4. - Install a set of good NOS tubes, and have the thing properly biased. (This isn't a mod). 5. - Have a cap job done if it needs it. (This isn't a mod either) A stock Princeton that's totally healthy puts out about 18 Watts. Putting in a more efficient speaker will gain you 1 or 2 dB. Putting in a Deluxe output transformer should get you yet another dB. The result will be a net gain of 2 to 3 dB in sound level, assuming everything else is ship-shape. That's about all you can do without resorting to unadvisable hacking. From [email protected] Thu Sep 26 01:10:10 CDT 1996 Article: 23490 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!news-peer.sprintlink.net!news-peer.gsl.net!news.gsl.net!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Simple Princeton mods? Date: 26 Sep 1996 01:49:19 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 13 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com >>>How much should the other mods cost? Increasing the phase inverter headroom is a matter of moving a wire or two inside the amp, say 15 minutes of bench time. Replacing the output transformer with a Deluxe transformer costs about $40 for the transformer and another half hour or so of bench time. Putting in decent preamp tubes you do yourself. You can get NOS 12AX7s for about $15 each. NOS 6V6s are uncertain. Whatever you pay for a matched pair, plus a little more bench time for biasing. From [email protected] Sun Nov 24 14:29:08 CST 1996 Article: 28435 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Fender Princetons? are they any good? Date: 24 Nov 1996 19:35:32 GMT Organization: AOL http://www.aol.com Lines: 27 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] You can get a little more poop out of a Princeyton if you want to do some work on it. As Tim mentioned, the stock phase inverter circuit falls way short on being able to drive the output stage all the way to saturation. However, you don't have to resort to such drastic mods as Tim talks about to fix it. Basically, the stock phase inverter lacks sufficient dynamic headroom to develop enough grid drive. That can be cured by moving that stage's B+ supply connection one step higher on the voltage divider in the power supply. Increase it's supply voltage, and you simultaneously increase it's headroom. Be careful to move only the phase inverter's supply to the next higher tap, and leave the remainder of the preamp where it is. You'll have to move a couple wires to do this. You may also, depending on several variables, need to rebias the phase inverter by changing the 1500 ohm bias resistor to 1200 ohms. Anyway, if you do this, the thing will then (with little room to spare) be able to fully drive the output stage. Be sure the output tubes are properly biased between 25 and 30 ma each at idle. You can also change the output transformer to that from a Deluxe if you want, it doesn't hurt. I have two friends with a brown Princetons. In both, I've put in the Deluxe transformer, and changed the 5Y3 rectifier tube to a 5AR4 to give more voltage to the output stage. Those amps now put out 18 Watts. I' ve also done the phase inverter mod alone to a 64 Princeton Reverb, and it also now puts out about 18 Watts. Lastly, unless you have the proper test equipment, maybe you should not tackle this yourself, because you'll need to look at the actual effects of your work using an o-scope to make sure you're achieving your goals. Princeton PI Headroom From [email protected] Sat Dec 7 10:10:04 CST 1996 Article: 29809 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!howland.erols.net!portc02.blue.aol.com!audrey01.news.aol.com!not-for-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Princeton reverb repair question Date: 7 Dec 1996 07:47:30 GMT Organization: AOL http://www.aol.com Lines: 8 Message-ID: <[email protected]> References: <01bbe1fd$aa783240$56233ccc@JSTIELAU> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] I'd take a close look at the control grid drive to the 6V6s, and compare it's peak amplitude to the headroom you have on the phase inverter. You may find that the phase inverter isn't driving one of the 6V6s fully into saturation. In other words, the phase inverter runs out of dynamic range and clips before the 6V6. This is a known problem with those amps. I've fixed it by giving the phase inverter more B+ voltage to work with. I move the phase inverter's supply lead up one notch on the power supply voltage divider. Problem solved. Princeton PI Heater Cathode v From no_spam_please@on_a_diet.com Wed May 27 16:18:34 CDT 1998 Article: 107270 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!worldfeed.gte.net!nntp.giganews.com!nntp.primenet.com!nntp.dist.maricopa.edu!not-formail From: Dutch Newsgroups: alt.guitar.amps Subject: Re: improving a silverface Princeton Date: Wed, 27 May 1998 14:02:46 -0700 Organization: Maricopa Community Colleges Lines: 15 Message-ID: <356C7F66.3183@on_a_diet.com> References: <[email protected]> <[email protected]> Reply-To: no_spam_please@on_a_diet.com NNTP-Posting-Host: mac47.stu-serv-2.sc.maricopa.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01Gold (Macintosh; I; PPC) Xref: geraldo.cc.utexas.edu alt.guitar.amps:107270 Tremolux wrote: > Anyway, if you move the B+ feed for the phase inverter one notch higher on the > power supply voltage divider chain, you solve the phase inverter headroom > problem. Why Fender never did this I can't figure. You have to watch out for the heater-cathode voltage. The max DC portion of this for a 12AX7 is about 100VDC. So, if the cathode's much above 100V, you could be running into trouble. The Schematic claims about 65V on the cathode, which means you've got /some/ room to go up. Just measure it after you move the wire, and if it's less than 100V, you're golden! Dutch From [email protected] Wed May 27 19:30:50 CDT 1998 Article: 107288 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: improving a silverface Princeton Lines: 4 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Date: 27 May 1998 22:26:06 GMT Organization: AOL http://www.aol.com References: <356C7F66.3183@on_a_diet.com> Xref: geraldo.cc.utexas.edu alt.guitar.amps:107288 >You have to watch out for the heater-cathode voltage. Been there, done that. Not an issue in this application. Princeton PI Mod Layout From [email protected] Mon Jul 12 12:50:51 CDT 1999 Article: 189184 of alt.guitar.amps From: Mike Tolomeo Newsgroups: alt.guitar.amps Subject: Re: Princeton reverb phase inverter mod (help?) Date: 12 Jul 1999 16:02:42 GMT Organization: Cornell University Lines: 21 Sender: [email protected] (Verified) Distribution: world Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: 128.253.230.46 X-UserAgent: Nuntius v1.1.1d7 X-XXDate: Mon, 12 Jul 99 17:02:34 GMT Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.gtei.net!news.maxwell.syr.edu!news.syr.edu!newsstand.cit.cornell.edu!usenet Xref: geraldo.cc.utexas.edu alt.guitar.amps:189184 In article <[email protected]> Steve Watson, [email protected] writes: >Tremolux responed to a query I made about this mod in an email, but >unfortunately, he assumed I could read a schematic. I used to have a >step-by-step description of how to do thjis, and even performed the >operation on a couple PRs I had in the past. Alas, I cannot read schematics, >I cannot find the printout of the instructions, and i'm not about to risk >damage to my sweet lil' BFPR without explicit instructions on how to do >this. >Can anyone help me out here? All I really need are some landmarks on the >circuit board (and maybe which lead on the PI tube gets moved) to guide >myself with. >Thanks in advance! >Steve If this is the mod where you increase the PI plate voltage, you can check out my notes at http://www.people.cornell.edu/pages/mt24/Amp/ Click on the "Increase headroom of a split load PI" link. I've got drawings of the layout--it's a silverface amp, but maybe it'll help. Princeton Reverb Power From [email protected] Fri Apr 3 15:24:40 CST 1998 Article: 95648 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsxfer3.itd.umich.edu!portc01.blue.aol.com!audrey02.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: SF Princeton Reverb Questions Date: 3 Apr 1998 16:35:48 GMT Lines: 22 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:95648 You guys are way off base here, you don't understand the circuits. First off, a totally healthy Princeton Reverb puts out closer to 18 Watts at the onset of visible waveform clipping (I have one, a 69, and I measured it). Secondly, the split-load type phase inverter's lack of gain does not necessarily limit the power output. There's plenty of gain from the input jack to the 6V6 grids to drive them into saturation. Bear in mind that this type of phase inverter is used on the old Tweed Pros that put out 35 or so Watts, it's used on Orange amps including the 80 Watters, numerous hi-fi amps, and I think a variation was used on the 200 Watt Marshall Major. The Princeton's power is limited by the plate voltages on the 6V6s and the output transformer. If your Princeton's split load phase inverter is running out of dynamic headroom before you can fully saturate the 6V6s, the fix is simple and you don't need to butcher up the circuit with bullshit phase inverter mods. It simply needs a higher voltage supply feed. Move the B+ feed line for the phase inverter one step closer to the rectifier in the power supply's voltage divider chain. I did it to mine and it worked perfectly. As a matter of fact, IMO all PRs could benefit from this simple mod. Princeton Reverb Tweaks From [email protected] Thu Jul 8 19:44:35 CDT 1999 Article: 188629 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.cwix.com!152.163.199.19!portc03.blue.aol.com!audrey03.news.aol.com!notfor-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: SF Princeton Reverb Question Lines: 93 NNTP-Posting-Host: ladder06.news.aol.com X-Admin: [email protected] Date: 08 Jul 1999 17:42:34 GMT References: <[email protected]> Organization: AOL http://www.aol.com Message-ID: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:188629 >Well hey Tremolux, (my tweed is a Tremolux), So is mine. A 59. >I have a 70's Princeton too, >that's why I felt comfortable saying keep it, it's a nice amp. Yep. Mine is a 69. > Is this tweak >easy to describe? Fairly. > Does it compromise the durability? Not really, but the extra power can make life a bit harder on the speaker. (As you would expect.) > Are you talking about >maybe adopting it to use 6L6's? > Hell no. Still uses 6V6s. No change in tone, no change in appearance, just a little louder. More of what you already have. No big deal. In most Princetons, the limiting factor in power output is that the phase inverter starts clipping before the 6V6s. Once the PI clips, there is nothing left to push the 6V6s any harder. The tweak simply gives the PI a bit more dynamic headroom so that the 6V6s clip first. You simply move the B+ feed for the PI up one notch on the power supply voltage divider. Give it more voltage to work with, it's dynamic headroom increases, and now you can drive the 6V6s all the way. Leave the B+ feed for the remainder of the preamp stages alone. Move only the PI. Up one step. That's it. Very simple. You just move a wire. One other thing I did, which is optional, is that the voltages in the Princeton are a bit lower than in it's bigger brothers. Yet it uses the identical circuit to drive the reverb pan. The lower voltages result in a lower drive level to the pan. IMO, the reverb sounds better if you can bump up the drive a tad. I did this by reducing the value of the 12AT7 cathode bias resistor from the nominal 2.2k to 1.8k. Running the tube at slightly higher current gives a tad more drive and livens up the reverb a tad. If you are happy with the way your reverb sounds now, just skip this. You can also help keep it from farting out by reducing the value of the coupling cap feeding the input of the PI. That split load PI circuit topology has a VERY high input impedance (several megohms) since the grid leak resistor is returned to essentially half the load (in the cathode leg), which follows the signal. That very high input impedance along with the stock input cap value result in lots of low end crap getting through which you don't need. I recommend using 1/4 the stock value. cleans up the low end fartyness with no loss in "real" low end tone. The stock speaker in these amps is a real limp-wristed turd. These amps respond amazingly well to a speaker improvement. The WeberVST C10Q seems to be the best choice, it can handle the (increased) power no sweat, it's WAY efficient (loudernhell) and had a vastly improved low end compared to the stock speaker. Yet it still has that classic Jensen style vibe. Try it, you'll like it. You do all these tweaks, you'll end up with a nice little Princeton Reverb that will rattle windows and is usable for small gigs. Yet it still looks stone stock, and sounds the same as before, only LOUDER. All tweaks are very easily reversed. No Torres level hacks or butchery. One last item, and this is to be considered as an optional option (think long and hard before doing it), is to replace the stock (somewhat wimpy) output tranny with one for a Deluxe Reverb. The DR unit has more iron, and fits perfectly (there was a second mounting hole already in the chassis to accept the increased leg spacing). I just bought a generic replacement DR tranny from Mojo for mine. IMO, this is the way Fender should have built the PR, but I'm sure they didn't because it then becomes too close in tone and volume to a real DR, and they needed more product differentiation. Oh well.... J. *You can guess what to remove from my email address to get rid of the spam block.* *Valid Spam Targets:* [email protected] [email protected] [email protected] [email protected] [email protected] ***** Princeton Vs Deluxe From [email protected] Tue Jan 9 13:19:48 CST 1996 Article: 7695 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!newsfeed.internetmci.com!in2.uu.net!news.ysu.edu!ns.mcs.kent.edu!tombstone.kent.edu!Phoenix!dgreene From: [email protected] (Dona Greene) Newsgroups: alt.guitar.amps Subject: Re: Why is Deluxe > Princeton? Date: 9 Jan 1996 15:05:32 GMT Organization: Kent State University Information Systems Lines: 14 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: phoenix.kent.edu X-Newsreader: TIN [version 1.2 PL2] : >Just curious... both 6V6 duets, both seem to have 400-420 plate voltage. : >Princeton 12 watts, Deluxe 20 watts. What gives? : >-: >-----------------------------------------------------------------------: >/* [email protected] "Less is more..." */ : >-----------------------------------------------------------------------Different power transformer and output transformer, both larger than a Princeton's transformers. This contributes to more power. Also, the Deluxe uses a GZ34 rectifier, whereas the Princeton uses a 5U4; the 5U4 has higher internal resistance and supplies less current. -Brad Bolton From [email protected] Tue Jan 9 13:20:01 CST 1996 Article: 7701 of alt.guitar.amps Newsgroups: alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!ix.netcom.com!netcom.com!rfries From: [email protected] (Robert Fries) Subject: Re: Why is Deluxe > Princeton? Message-ID: Sender: [email protected] Organization: NETCOM On-line Communication Services (408 261-4700 guest) X-Newsreader: Forte Free Agent 1.0.82 References: <[email protected]> <[email protected]> <[email protected]> Date: Tue, 9 Jan 1996 16:19:49 GMT Lines: 27 [email protected] (Dona Greene) wrote: >: >Just curious... both 6V6 duets, both seem to have 400-420 plate voltage. >: >Princeton 12 watts, Deluxe 20 watts. What gives? >: >->: >----------------------------------------------------------------------->: >/* [email protected] "Less is more..." */ >: >----------------------------------------------------------------------->Different power transformer and output transformer, both larger than a >Princeton's transformers. This contributes to more power. Also, the >Deluxe uses a GZ34 rectifier, whereas the Princeton uses a 5U4; the >5U4 has higher internal resistance and supplies less current. > -Brad Bolton Also, very important - significantly different phase inverter. Robert ***************** Robert Fries [email protected] 415.988.9475 ***************** Princeton driver mods From [email protected] Tue Jan 7 10:28:45 CST 1997 Article: 33482 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsfeed.internetmci.com!news.campus.mci.net!n-f-m From: "murali@kalimusic" Newsgroups: alt.guitar.amps Subject: ADD GAIN TO SF PRINCETON Date: Mon, 06 Jan 1997 20:07:41 +0000 Organization: Kali Music on the Internet Lines: 90 Message-ID: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: s09-pm06.snaustel.campus.mci.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0Gold (Macintosh; U; 68K) CC: Scott A Warren On Sun, 5 Jan 1997, Kali Music wrote: > Ffgtr wrote: >> > > About a week or two ago, there was a bit of traffic concerning Hoffman > > Amps. cheers > > I was in Sarasota last week and stopped by to meet Doug and try his > amps. (snip) > He also helped me with ideas on adding a gain stage to a '72 Princeton > that was gutless. Now this cutie has so much gain I have to keep her on > a leash! Thanks, Doug, if you're *listening*. > Murali >> Could you detail that mod? A friend has the same amp, and he is dying for a little more gain. Thanks. Scott Warren OK! Please note that you lose the trem with this mod. Gecherself a schemo of the AA1164 Princeton Reverb and a schemo of the AA964 Princeton. You will see that the PR has a gain stage using the second half of the 7025. This is the stage that is missing in the AA964 Princeton. You *insert* this stage between the volume control and the second half of the 7025 shown on the AA964 schemo. You have the option of using either the half of the tremolo/phase inverter 12AX7, or, as I did, using the other half of the 7025 (1st preamp tube). It's just a question of where you want the tone recovery amp stage to be in terms of how the leads are physically located in the chassis. *******I don't want to be a killjoy, but I feel that if you can't read a schematic enough to figure this mod out, you should probably have a tech do it for you.***** The voltages are lethal and you might just screw up your amp and have a very expensive repair bill. A competent, reputable tech should be able to perform this mod for about $50. FIRST: I tore down the entire trem circuit and opened up some space on the eyelt board. Then I proceeded to assemble the parts necessary and built the new circuit in a convenient location on the eyelet board. NOTE that you will have to disconnect the negative feedback circuit, or switch the wire going to the 2K7 ohm resistor to the black output trans. wire (ground) or your amp will OSCILLATE! NOW: I went a step or two further and routed ALL the leads under the circuit board, the way I believe Leo intended. This is not too bad (time wise) on something as simple as a Princeton, but it will increase the cost of having a tech do it. THEN: I used the Intensity Control to vary the bias by running a 1 Meg resistor to ground from what was the brown lead on the Intensity pot. This enables you to vary the negative bias resulting in about 15ma difference from 1 - 10 on the pot. I don't recall offhand, but I might have tweaked the bias feed resistor a bit to get the tubes to 25ma at idle with the Intensity Control at 1 (off). So you are now able to get your tubes anywhere from 25 to approx. 40ma. You WILL hear the difference. BUT: don't use Sovtek 6V6s! They won't last long at 40ma......... SO, now you've got this absofuckinglutely SCREAMING Princeton and your wife or girlfriend or neighbor loves the tone but has a REAL PROBLEM with the volume. Take the Speed Control and turn it into a Master Volume by interupting the circuit, going into the Speed Control (lug that has a Blue wire) from the output of the last gain stage, and going >from the wiper of the Speed Control (center lug) to the Phase Inverter, denoted by the letter "X" in the box on the AA964 schemo. AND you have tamed the beast. There are a few tweaks you could try, like a 2M2 ohm resistor in place of the 3M3, or different value caps to bypass this resistor (or no cap at all). Or you could put in a push pull pot that lets you bypass the tone stack completely. WOW: talk about gain. Or different value caps in the new gain stage to voice the amp just right. These are really fun amps to work with but please be careful. OH, uh, one more tip: RUN, don't walk, to your nearest tube outlet and pick up some NOS 6EY6 tubes. Use 'em in place of your Sovtek 6V6s (or any other 6V6s that you're not happy with). You can probably find them for about $5 each (YES! NOS American made tubes that sing for only $5!!!!). They spec out very, very close to 6V6s, though I've been warned by Tremolux you may need to reset your bias slightly lower (more negative volts). I have not found that to be the case in my TV front Deluxe, though. I plugged 'em in, turned it on, measured the bias and they came up exactly the same as the NOS 6V6s I had been using. Sound awesome, dude. The only question I have is how long they'll sound good. But see if you can find Mullard or Tung Sols or something good like this and they should last as long as any good 6V6. I would appreciate hearing how they like it, from anyone who tries this mod. I tip my hat to Doug Hoffman for the basic idea, and to Tremolux for the 6EY6 tube tip. (Always remember to thank your Gurus, dude!) Good luck and enjoy the sustainnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn................................. m. Princeton tone bypass From [email protected] Thu Nov 14 11:04:09 CST 1996 Article: 27440 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsfeed.internetmci.com!news.campus.mci.net!notfor-mail From: murali Newsgroups: alt.guitar.amps Subject: Re: Fender Princetons? are they any good? Date: Thu, 14 Nov 1996 02:55:35 +0000 Organization: CampusMCI Lines: 57 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: s03-pm12.snaustel.campus.mci.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0Gold (Macintosh; U; 68K) [email protected] wrote: > > someone wrote: > >Nick, I'd have to disagree with this (although I do agree with the > >rest of your posting). Except for the ground switch, which was added > >around 1970, the silverface Princeton Reverbs up through the late > >'70s are electrically identical to the blackface amps. > > Any of you technogods want to confirm or deny that? > > NS > > <><><><><><<><> Don't cut up a good untouched one. Even the silverfaces are > guaranteed to become collectible in the next few years because of their > unaltered by the "evil" CBS circuitry. In my opinion there is not a better > garage sized or home recording amp made by anyone than the old Princetons > and Deluxes(although a Deluxe can get VERY loud). > Jeff Deasey > DLS > Builder and Repairman to the NON-Stars!!!! > Ontario, California Once again I agree. The push pull switch on my '72 SF Princeton toggles between a. .0047 mfd cap wired directly from pin 1 of V1 to the Volume control (bypassing the tone controls), and 620 pfd (two caps: 500 pfd + 120pfd paralleled) between pin 1 and the tone circuit. With the .0047 clicked in, and the tone controls bypassed, the sag is amazing, sounding very punchy, like quick attack 4:1 compression, especially playing on the G, B, and E strings with a strong attack. I also tried different V1s: the GT ECC83 is the easiest to overdrive compared to 12AX7A, 12AX7A R, and 12AT7. 620 pfd (switch pushed "in" and treble and bass controls engaged) almost eliminates the compression and gives more midrange and less brilliance than the stock 250 pfd, though still pushing V1 a bit harder. Model 5C2 (c. 1948) uses .0005 mfd between the tone and volume control (which = 500 pfd), as does the Brown 6G2 that our friend in Hawaii was so fortunate to find. One difference between 6G2 and AA964 is the +100 vdc change in plate voltage out of the GZ34 rectifier, but a comparison of the schematics shows they have alot in common. "Actually the SF and BF Princeton trems work on the power tubes also. But as far as getting a fat and nasty tone, your brown amp would be all over them. Tim" I'd like to have both these amps (6G2 and offspring) in one room to compare. I'd be willing to bet the AA964 can easily be tweaked to back to Brown. Mine has a 20 oz. ceramic magnet 10" Eminence and it does fat and nasty real good. I just found a '70 Oxford 10" taken from a Princeton to put into mine. Can't wait to try it out. your friend Murali Princeton with 5881s From [email protected] Mon Jan 15 16:45:50 CST 1996 Article: 8022 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!newsfeed.internetmci.com!in2.uu.net!nntp.news.primenet.com!news.primenet.com!miker From: Mike Rejsa Newsgroups: alt.guitar.amps Subject: Re: 6L6/5881 in a Deluxe?? Date: 15 Jan 1996 08:01:01 -0700 Organization: Primenet (602)395-1010 Lines: 22 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> X-Posted-By: [email protected] Thomas Madden wrote: : thought Princetons must NEVER use a solid-state : rectifier....whats the deal??? Never never... if you have the stock 6V6's, because they can't take the higher voltage. However, the thread here is about converting to 6L6s or 5881s. *Now* the problem is not overvoltage, its too much heater current. If you use a solid state rectifier, you gain the 15w of power that the 5U4 heater is burning up. This makes up for the additional 5.7w loss of a pair of 5881s. Distilled answer: (Princeton specific) 1. If you have 6V6s, you *can't* use a ss rectifier. 2. If you convert to 5881s, you *have* to use a ss rectifier. ------------------------------------------------------------------------/* [email protected] "Less is more..." */ -----------------------------------------------------------------------From [email protected] Tue Jan 16 21:55:25 CST 1996 Article: 8109 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!newsfeed.internetmci.com!in1.uu.net!prodigy.com!usenet From: [email protected] (Joseph Pampel) Newsgroups: alt.guitar.amps Subject: Re: 6L6/5881 in a Deluxe?? Date: 16 Jan 1996 05:37:27 GMT Organization: Prodigy Services Company 1-800-PRODIGY Lines: 27 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: inugap4.news.prodigy.com X-Newsreader: Version 1.2 Thomas Madden wrote: > >thought Princetons must NEVER use a solid-state >rectifier....whats the deal??? "never" is a dirty word really.. What I think people mean when they say things along these lines, like "a Deluxe Reverb or a Princeton must Never use a solid state rectifier" is not that the amp circuit can't take it, but that the 6V6 output tubes are already getting enough of a beating and you shouldn't raise their B+ anymore. (which is what would happen if you installed a solid state rectifier.) If you changed to other output tubes, say 5881's, you could switch to a solid state rectifier, and in fact it would be advisable to free up every extra bit of current the power tranny could deliver since the 6L6/5881 uses a lot more filament current and will really overheat a Princeton PT. losing the tube rectifier will save that PT 2 to 3 amperes of current (which it would have used to light the rectifier tube filament) and would in fact increase its abilities to deliver more current on its other windings so the 5881's wouldn't be as much of a problem (though still less than ideal probably) I'd personally advise leaving Princetons alone, as they don't benefit IMO from output tubes swaps as much as the Deluxe can. The Deluxe rvb has a bigger power supply, better output tranny and more drive >from the pre-amp all of which lends itself to being a better candidate for a tube swap. Joe Pro Reverb History From [email protected] Tue Sep 10 11:18:27 CDT 1996 Article: 22384 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!howland.erols.net!panix!news.panix.com!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar,rec.music.makers.guitar,rec.music.makers.guitar.jazz,alt.guitar.amps Subject: Re: Opinion/Identify Fender amp Date: 9 Sep 1996 23:39:04 -0400 Organization: Panix Lines: 48 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix3.panix.com Xref: geraldo.cc.utexas.edu alt.guitar:113192 rec.music.makers.guitar:107454 rec.music.makers.guitar.jazz:7761 alt.guitar.amps:22384 GMF wrote: >Description: Fender Pro Reverb > 2 x 12" speakers > Year is unknown to me but there is a serial number > on the back: A 19836 (maybe it's an '83 model?) > >What years were these made? I haven't the slightest idea. > >Any advice about a fair price or opinions about its tone will be >appreciated. Please reply by e-mail to the address below. Thanks. Pro Reverbs were first sold in mid-1965. Since CBS bought out Fender in January of 1965, all of them are post-CBS Fenders. Even so, some have "Fender Electric Instruments Co." on the front panel under the Pro Reverb Amp logo instead of the CBS era "Fender Musical Instruments." All the original Pro Reverbs are "blackface" -- they have black control panels with white lettering, script logo, silver/black/white grille cloths, raised Fender logo on the grille cloth and black Tolex covering. They use two 5881/6L6GC power tubes and are rated at roughly 40 Watts. They have two channels, one of which has both reverb and tremolo; a dual footswitch controls the effects. In excellent condition, with original speakers these amps selling for between $650 and $850. Mint examples sell for more. In 1967 Fender changed styles. The front panel was polished aluminum ("silverface") and blue block lettering. The grille cloth now blue threads added. The cabinet grew an inch in depth, about the same in height, and became more angular around the front panel. An aluminum trim strip surrounded the speaker panel for roughly one year. The circuitry stayed the same as the blackface amps until roughly 1968 when CBS added their ill-received modifications; the worst of these were removed by 1969. These amps are currently selling for roughly $400 to $550. In the mid 70's a master volume control was added. These are perhaps the least desirable of the Pro Reverbs, along with the later 1980-era blackface versions, and sell for $300 to $400. They were discontinued in 1982. -Len Moskowitz Core Sound WWW site: http://www.panix.com/~moskowit [email protected] Pro Reverb Orig Speakers From [email protected] Sat Dec 27 10:19:09 CST 1997 Article: 77544 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!howland.erols.net!portc02.blue.aol.com!prodigy.com!nntp.earthlink.net!usenet From: unclespot Newsgroups: alt.guitar.amps Subject: Re: Utah speakers in BF Pro reverb Date: Fri, 26 Dec 1997 19:50:52 -0800 Organization: Uncle Spot Inc. (http://home.earthlink.net/~unclespot/) Lines: 12 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: 153.37.7.109 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01Gold (Win95; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:77544 Ingo, I've seen Utah, Oxford, and Jensen speakers common in Pro Reverbs. When I first started repairing Fender amps in the late '60s some people put some JBL D120s in their Pros also (but, to my knowledge they did NOT come from Fender like that, like the Twin-Reverbs did - I may be wrong, but have never seen them stock...) As far as what sounded the best...most people liked the Jensens, then the Utah, and then the Oxfords... they all seemed pretty close to me at the time. Now I've been replacing them with WeberVST P12N or P12Q speakers... they are a great replacement speaker for a gigging musician! If you were a collector I'd recomend a "stock" speaker... later, Ron Pro Reverb Parts From [email protected] Mon Nov 27 16:55:08 CST 1995 Article: 5851 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!news.inc.net!news.uoregon.edu!mars.efn.org!garcia.efn.org!notfor-mail From: [email protected] (Jeff Olsen) Newsgroups: alt.guitar.amps Subject: Re: Best source of parts for a '68 Pro Reverb? Date: 27 Nov 1995 12:13:28 -0800 Organization: Oregon Public Networking Lines: 23 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: garcia.efn.org X-Newsreader: NN version 6.5.0 #7 (NOV) In <[email protected]> [email protected] (Mic Kaczmarczik) writes: >Someone I know is restoring a '68 Pro Reverb (early silverface with >aluminum trim around the grill). The amp is missing the ``Fender'' >script logo on the grill and the jewel for the ``on'' lamp. Can >anybody recommend a good place to get these parts? >Also, the amp is loaded with E-V Force 12 speakers, which obviously >are not stock. What sort of speakers would it originally have come >with? Try Mojo Musical supply; 1-800 927 6656 for the logo and the jewel. If they don't sell to callers (IE, only to dealers) I can order it for you through my work. Don't know about the speakers, but I may know someone who'd buy those Force 12's from them. It would, in general, have had a low wattage, paper-cone speaker by Jensen or Utah in it... I have one. They are KILLER amps. He should look at putting new filter capacitors in there, and new tubes too... -jeff From [email protected] Wed Nov 29 08:13:46 CST 1995 Article: 5927 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!rockyd!cmcl2!panix!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps Subject: Re: Best source of parts for a '68 Pro Reverb? Date: 29 Nov 1995 00:17:51 -0500 Organization: Panix Lines: 23 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix3.panix.com Mic Kaczmarczik wrote: >Someone I know is restoring a '68 Pro Reverb (early silverface with >aluminum trim around the grill). The amp is missing the ``Fender'' >script logo on the grill and the jewel for the ``on'' lamp. Can >anybody recommend a good place to get these parts? Check out the advertisers in Vintage Guitar magazine. The old Fender logos are not cheap -- expect to pay around $50 for them. You can get the pilot light jewels for around a buck ($1). >Also, the amp is loaded with E-V Force 12 speakers, which obviously >are not stock. What sort of speakers would it originally have come >with? The '66 and '72 Pro Reverbs I have both have Oxfords. -Len Moskowitz Core Sound WWW site: http://www.panix.com/~moskowit [email protected] Pro Reverb Questions From [email protected] Fri Feb 2 18:26:04 CST 1996 Article: 8907 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!usc!ccnet.com!rahul.net!a2i!bug.rahul.net!a2i!ddsw1!news.mcs.net!usenet From: Al Newsgroups: alt.guitar.amps Subject: Re: Fender Pro Questions Date: Wed, 31 Jan 1996 06:58:48 -0600 Organization: MCSNet Internet Services Lines: 31 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: alsnt.image.ctt.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0b6a (WinNT; I) Ken Cutler wrote: > > Hello to all you Fender Amp heads. I've a few questions about my > blackface Fender Pro Reverb. > Second question: I was fixing a bad ground (and replaced the power > cord with a three-wire set-up), and decided to try adjusting the output > bias by ear. Since then, I acquired a schematic for it, which indicates > a recommended -51V at the grid bias resistors junction. Should I go with > this? The AB165 Pro Reverb sometimes gets a bad rap because it was sold only as a CBS amp. My guess is it was one of Leo's last projects! The Circuit is identical to the highly regarded AB version of the 1x15 Vibroverb and with the exception of the Middle control, the AB Super Reverb. Kendrick doesn't like the output transformer, but if you check the numbers, it's the same one used on the Bandmaster! 6L6's will generally bias properly somewhere between 48 to 55 volts in these amps. Biasing by current is better, if you're looking for clean sounds try between 30 to 35 ma per tube. Of course all the caustions apply. There are 2 schools of thought on the 470ohm screen resistors. The other is NOT to increase the wattage rating since these resistors protect the power transformer if a power tube shorts screen to grid. There is also a 470 ohm resistor in the bias circuit (next to the diode on the small fishboard). IMHO, I would rather replace resistors than power transformers. Definately agree about using flameproof resistors though! A lot of Pro Reverbs came with Utah speakers. You can get Jensens, either original or reconed from many Vintage dealers - Check out Vintage Guitar News-Magazine. From [email protected] Fri Feb 2 18:26:31 CST 1996 Article: 8926 of alt.guitar.amps Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.io.com!imci4!imci5!suckfeed.internetmci.com!news.internetMCI.com!newsfeed.internetmci.com!swrinde!sgigate.sgi.com!sgiblab!news.spies.com!genmagic!bug.rahul.net!a2i!ddsw1!news.mcs.net!usenet From: Al Newsgroups: alt.guitar.amps Subject: Re: Fender Pro Questions Date: Fri, 02 Feb 1996 06:57:12 -0600 Organization: MCSNet Internet Services Lines: 19 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: alsnt.image.ctt.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0b6a (WinNT; I) Mark Garvin wrote: > > In <[email protected]> Al writes: > > >There are 2 schools of thought on the 470ohm screen resistors. The other is > >NOT to increase the wattage rating > Problem with under-wattage carbon comps is that they'd just as soon > decrease in value as increase. Check the resistance next time you > see a toasty-looking one. I've seen this happen with originals, but have not experienced any problems with modern high quality flameproofs doing this. Even so, I'd still rather blow a tube as opposed to a transformer. In my own amps, I check all the power circuit resistors whenever I change tubes. Learned about this after once having the 'pleasure' to inform the owner of a nice SVT that his power xformer was dead because someone who had the amp before was tired of replacing resistors every time a power tube blew & upped all the wattage ratings. Ken Fisher also subsribes to this same theory & I believe Kendrick does too. Pro Reverb Speakers From [email protected] Fri Feb 9 20:16:19 CST 1996 Article: 9411 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: Eminence "Jensens" in Pro Reverb? Date: 9 Feb 1996 19:15:43 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 36 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: newsbf02.mail.aol.com X-Newsreader: AOL Offline Reader In article <[email protected]>, brotone writes: >1. Does anyone have any experience w/ the Eminence-made "Jensen" >copies that Sovtek/New Sensor is selling? (either the paper or Kapcon >voice coil versions?) Specifically, how might they sound in a Pro? My >"project" Pro has some '80 Eminences in it, and one definitely has a >dragging voice coil, so I'm figuring to replace them both. Or should I >just spring for the Mojo's? >2. Anyone ever run into a transition-era amp w/ the wrong tube chart >in it? Mine is a '68 aluminum-trimmed silver face. While the tube >chart definitely says AA165, the circuit was definitely AA668 (or >maybe it's AB668; I never saw a schematic, only heard about it from a >friend.) In any case, it had some screw-ball bias circuit and huge >1500 ohm, 7 watt resistors from cathode to ground on the 6L6's. Might >this mixup have happened at the factory, or have I been baited and >switched? (Actually, it doesn't really matter, as I have changed >everything back to b..f specs. I'm just curious.) >thanks, All of these Alnico magnet speakers are made by Eminence. The original speakers in a Pro Reverb were ceramics, Eminence also makes some fine ceramic replacements, in fact I just sold a pair to a guy for a BF Pro Reverb, he is delighted. I have seen quite a few transitional Fender amps with incorrect tube charts, most notably AB763 (black face) charts on Super Reverbs that had all of that fine silver face circuitry. Those are actually 150 ohm resistors, the output section is partially cathode biased and partially grid biased. If anyone has an explanation for this I would be most interested. ...Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. Pro Reverb baffles From [email protected] Sun Oct 8 22:32:02 CDT 1995 Article: 4246 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newsfeed.internetmci.com!newsxfer.itd.umich.edu!news.eecs.umich.edu!panix!notfor-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps,alt.guitar,rec.music.makers.guitar Subject: Re: Info on Pro Reverbs Date: 8 Oct 1995 16:15:37 -0400 Organization: Panix Lines: 13 Message-ID: <[email protected]> NNTP-Posting-Host: panix3.panix.com Xref: geraldo.cc.utexas.edu alt.guitar.amps:4246 alt.guitar:62168 rec.music.makers.guitar:66354 I have another data point regarding differences between the Pro Reverbs with the removable baffle (blackface and pre-1972 silverface). The earlier ones have a baffle that's 15 and 1/2" high. The later ones are 16 and 1/2". Overall height differs by one inch too. It doesn't look like a JBL D-130F 15" driver will fit in the '65 - '71 Pro Reverbs. I'll be buying a new cabinet for my '65. -Len Moskowitz [email protected] Pro with a 15 From [email protected] Wed Mar 13 23:32:44 CST 1996 Article: 11403 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!usc!chinews.cic.net!nntp.coast.net!sgigate.sgi.com!swrinde!cssun.mathcs.emory.edu!gatech!newsfeed.internetmci.com!panix!notfor-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps,alt.guitar Subject: Re: 15" speakers for guitar? Date: 13 Mar 1996 09:53:59 -0500 Organization: Panix Lines: 20 Message-ID: <[email protected]> References: NNTP-Posting-Host: panix3.panix.com Xref: geraldo.cc.utexas.edu alt.guitar.amps:11403 alt.guitar:84264 In article , Ericb wrote: >Does anyone out there use 15" speakers for guitar playing? The old pre-65 Fender Pro combo amp used a 15". I replaced the baffle in my '66 blackface Pro Reverb with one from Paul Lamb (via Mojo) that holds a '58 JBL D-130F. Very SRV sounding. The 15 is very clean and efficient. The amp (with its stock tube rectifier) is clean until it starts to distort, and then the tube grunginess/compression comes through beautifully. Great low end. High end is beamy -- get off axis and it drops very quickly -- but on-axis it's just fine. No screechy edge at all. The JBL's aluminum dome also looks very cool through the Fender grill cloth. -Len Moskowitz Core Sound WWW site: http://www.panix.com/~moskowit [email protected] Proper Blackfacing From [email protected] Wed Aug 19 19:08:38 CDT 1998 Article: 122474 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!newsfeed.internetmci.com!192.220.250.21!netnews1.nw.verio.net!netnews.nwnet.net!nntp.ni.net!nnrp2.ni.net!notfor-mail From: "johng" Newsgroups: alt.guitar.amps References: Subject: Re: More than one way to blackface an amp? Lines: 71 X-Newsreader: Microsoft Outlook Express 4.72.3110.1 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Organization: Cyberverse, Inc. Message-ID: <[email protected]> Cache-Post-Path: [email protected] Cache-Post-Path: [email protected] Date: Wed, 19 Aug 1998 20:20:57 GMT NNTP-Posting-Host: 209.151.224.37 NNTP-Posting-Date: Wed, 19 Aug 1998 13:20:57 PDT Xref: geraldo.cc.utexas.edu alt.guitar.amps:122474 Jim Kroger wrote in message ... yadda...yadda...yadda.... >My very knowledgeable friend John Greene said he clipped >the power tube grid resistors (in his DR), changed four >resistor values in the phase inverter, and did something >with one of the caps in the PI. He also noted the increase >in bass response. I'm a bit mystified as to whether the techs >are doing something else in addition, or what. Well, you almost got it right... ;) I clipped the 1200pF snubbing caps on the grids of the power tubes. I changed the 47K plate resistors on the phase inverted to 82K/100K. I changed the 330K resistors on the grids of the phase inverter to 1Megs, and finally I changed the coupling capacitor on the input to the phase inverter to a .001uF. The 1200pF caps on the power tubes suck tone big time and are definitely worth taking off. IMHO, I think the 330K/1Meg & .01uF/.001uF change was done by Fender to compensate for the lack of low frequency response in the Oxford and later Utah speakers. It gives these speakers back some of the bottom end but cause the amp to start distorting at a much lower level. Again, that's just my take on it. (a generous helping of personal opinion follows...) I think the change to 47K plate resistors was to try and compensate for the loss of high frequency response the 1200pF capacitors caused. They didn't want to get rid of the caps because it would require more careful assembly work to keep the output stage from oscillating, more careful work == higher manufacturing cost. I tend to think whoever put the 1200pF caps in there to begin with figured that with the series 1500 resistors the rolloff frequency would be up around 88KHz, no harm-no foul. However, what wasn't taken into account was the impedance of the 1200pF being in parallel with the 220K bias resistors and how it loads down the phase inverter. With the caps installed, the gain of the phase inverter has a significant drop in gain at just over 1KHz. By reducing the value of the plate resistors to 47k, this corner frequency moves up to around 2KHz with an overall gain reduction of a little more than 3dB, better but not good enough. >Is there a correct approach to blackfacing? Why, if >they are all emulating the same schematic, is there >disagreement? There really shouldn't. I think the disagreement comes in because of conversions that are only done part way, i.e. the components are changed but the speaker isn't. When I first Blackfaced my 74 DR, I left the original Utah speaker installed. The amp sounded thin and weak after the change. I didn't like it at all. So I changed the 1Megs back to 330K and the .001uF coupling cap back to a .01uF. However, once I put a Naylor in there I changed them back again and tone city! The only thing left to make it a *True* BF conversion would be to replace the power transformer with a BF transformer so I could use a GZ34 rectifier tube. I suspect that the major difference this makes would be apparent more when the amp is cranked, something I rarely do so I haven't bothered with it. The best part about Blackfacing a DR is that it is just component value changes, very easy to change back if you don't like the results. --john greene Pull Boost Failures From [email protected] Mon Nov 18 19:18:26 CST 1996 Article: 27822 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!psinntp!psinntp!portc01.blue.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: old vibrolux reverb Date: 18 Nov 1996 20:07:19 GMT Organization: AOL http://www.aol.com Lines: 13 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com > By the way, while the pull boost and master volume were >unnecessary, silly additions to the design, it has not been my >experience that they make the amp less reliable. Not the master volume, but the pull boost can cause prematurre failure of the reverb drive 12AT7, it's cathode resistor any bypass cap. In most of the amps so equipped, they obtained the boost signal from the reverb drive circuit, and changed the biasing on the 12AT7. Specifically, they went to a much smaller cathode resistor, causing the tube to run MUCH hotter. I've seen these tubes fail short from overheating and take out the cathode circuit. If you have a pull-boost amp and you want reliability, at least rip out that pull boost bullshit and put the proper BF era biasing back on the 12AT7 cathode. RI Bassman Mods From [email protected] Mon Nov 4 08:51:39 CST 1996 Article: 26469 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!news-peer.sprintlink.net!newspeer.gsl.net!news.gsl.net!news-stock.gsl.net!news.gsl.net!van1s03.cyberion.com!news From: O'Connor Newsgroups: alt.guitar.amps Subject: Re: '59 Bassman Reissue (Help!) Date: Mon, 04 Nov 1996 06:12:47 -0800 Organization: London Power http://www.wwdc.com/~power/ Lines: 42 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: pm38.wwdc.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0 (Win16; I) > >Help! I bought a '59 Fender Bassman Reissue because a buddy has one > >that sounds great! But mine sounds too bright and brittle. I turn the > > >treble, presence and bass to "0" and the middle to "5" and I still get > >the bright sound!! Are there any mods that will "warm up" the amp? A customer of mine had the same complaints about his "re-issue" Bassman. The amp is not an exact copy of the 59, so there are a couple of things you can have a tech do: 1) There are likely to be rattling problems if you try the tube rectifier route. I installed a couple of power resistors in series with the solid-state rectifiers to achieve tube-like sag with better reliability and no tube rattles! 2) Replace the 'presence' pot with a 1-meg audio taper 3) Add a pair of 1k5 grid-stopper resistors to the power tubes (one per tube) 4) Rewire the 'presence' control to be a 'cut' by: slashing a trace on the control PCB; move the end of the 4k7 to ground; with a shielded 2-wire cable, tie the new pot across the grid-leak side of the 1k5 grid-stoppers, with a 5nF-400V plastic cap in series with one of the pot leads (NOTE: You only have to use the wiper and one end of the pot) 5) For best versatility of tube selection; Add a second bias circuit and connect the existing one to one power tube and the new one to the other. This allows hum-free performance to be obtained from any set of tubes. 6) Install some 1-ohm current sense resistors in series withpin-8 of each power tube to ground. This makes reading bias currents a lot easier and safer (than the transformer-shunt method). The grid-stoppers roll off the high end a little in the power amp, and makes the circuit truer to original form. The re-wired 'presence' gives at '10' what tone you used to have at '1'-- now you can smooth out the highs at will, while a non-zero setting of your 'treble' pot allows some high-end sparkle. These mods allow a mellow vintage tone to be obtained from the new amp, with greater reliability. Red Knob Twin problems From [email protected] Fri Sep 12 15:02:32 CDT 1997 Article: 63411 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!vixen.cso.uiuc.edu!howland.erols.net!newspeer.sprintlink.net!news.sprintlink.net!Sprint!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: "The Twin" as bad as Blues Deluxe? Date: 12 Sep 1997 08:51:13 GMT Organization: Netcom Lines: 49 Message-ID: <[email protected]> References: <01bcbea4$e4dfafb0$610258aa@alsnt> NNTP-Posting-Host: den-co10-27.ix.netcom.com X-NETCOM-Date: Fri Sep 12 3:51:13 AM CDT 1997 Xref: geraldo.cc.utexas.edu alt.guitar.amps:63411 In [email protected] (M. P. Gilbert) writes: > >Thanks everybody, but nobody's answered the question! I know you just have >to mention Fender on this group for readers to leap on their particular >soapbox, but what I asked was: Is "The Twin" built better than the Blues >Deluxe? And I don't the new "Twin Amp" I mean the red-knobbed one. Now >please try and concentrate your minds. Thankyou. Lord Valve Speaketh: The red-knob "The Twin" is a screamin' piece of shit. It's hard as hell to service, the HV supply sucks, the bias circuit is flaky, and you can't even clean the pots without removing a circuit board. The jacks break all the time. The pots come apart easily whenever they get smacked into something, which is EVERY TIME YOU MOVE IT, due to the fact that those ugly-ass red knobs stick a mile out in front of the amp. The overdrive (like all Fender overdrive) sounds hideous. It's a LOUD amp, but very sterile-sounding. Maybe steel-guitar pickers would like it. I wouldn't buy one unless I had a fireplace. The Blues Deluxe has cheesy pots, and the PCB-mounted preamp tube sockets fail a lot. The overdrive is better than the red-knob Twin, but not much. The reverb is IC driven, and sounds wimpy. Repairs on the Blues Deluxe are difficult...most operations require removal of the PCB, which is difficult (and hard on the ribbon cables which connect the main board to the tube board.) The jacks are crap. The relays are not well-sealed, and tend to go screwy from cigarette smoke in nightclubs. No bias control, so you have to replace a resistor to re-bias. Comes biased WAY cold from the factory, and sounds like hell that way. It WILL benefit from a rebiasing, by the way. If someone was pointing a gun at me and hollering "CHOOSE," I'd take the Blues DeLuxe, because it has tweed covering and chickenhead knobs, and it's a lower-powered amp that can be cranked up for real overdrive. And you CAN diddle it up to get it sounding halfway decent. But...I'm going to echo most of the other folks on this thread, and advise you to find yourself a silverface of some kind and have a good tech BF it for you. NOS power tubes, Ruby STR-7025s in the 12AX7 holes, and NOS 12AT7s where required. You WON'T be sorry. Lord Valve Reduce Champ Screen Voltage From [email protected] Fri May 5 22:56:42 CDT 2000 Article: 249337 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!portc.blue.aol.com.MISMATCH!portc03.blue.aol.com!audrey05.news.aol.com!notfor-mail From: [email protected] (Hack butchers suck) Newsgroups: alt.guitar.amps Subject: Re: New 6V6EH tubes: bad batch? Lines: 27 NNTP-Posting-Host: ladder06.news.aol.com X-Admin: [email protected] Date: 06 May 2000 02:57:22 GMT References: <[email protected]> Organization: AOL http://www.aol.com Message-ID: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:249337 >Also, adding a >screen resistor would be a good idea. I use 1K ohms, >but I've seen them at anywhere from about 470 ohms >up to about 1.5K ohms. > You've hit upon a great way to basically keep the plate voltage and cathode bias circuit stock and yet reduce the static plate current.....drop the screen voltage. IMO the weak spot in all those commie 6V6s is the damn screen grids. Try about a 2.2k (or maybe even larger) @ 2 Watt resistor in series with the 6V6 screen. If the value here gets large, you may want to add another filter cap from the screen to ground, about 10 uf would be plenty. *You can guess what to remove from my email address to get rid of the spam block.* *Valid Targets:* [email protected] [email protected] [email protected] [email protected] ***** X-no-archive: yes Replacing Glued Baffles From [email protected] Thu Jan 1 12:01:03 CST 1998 Article: 78234 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!newspeer.sprintlink.net!news.sprintlink.net!Sprint!worldnet.att.net!newsadm From: Rich Koerner Newsgroups: alt.guitar.amps Subject: Re: replace SF glued baffle? Date: Thu, 01 Jan 1998 07:01:31 -0500 Organization: Time Electronics Lines: 106 Message-ID: <[email protected]> References: Reply-To: [email protected] NNTP-Posting-Host: 12.68.34.180 Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Mailer: Mozilla 3.03Gold (Win95; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:78234 [email protected] wrote: > > Any tips on replacing the baffle board on a silver face Fender with > glued-in baffle? My Method for Removing the Baffle from a CBS Type Fender Cabinet. It's a lot of work to do it right. First Remove carefully the top piece of tolex and peel back the sides to expose the corners. Then using boiling water, soak the inside and outside of one of the top corners to soften the glue. Apply 3-4 times after it soaks in. Keep at it, just takes time to soak in and soften the glue. (Note - Do one corner for a combo cabinet to keep the top joined to one side. Soak both corners for a speaker cabinet, to later completely remove the top.) With a large heavy shot loaded dead blow hammer and a piece of 2x4, place the 2x4 Flat against the top in the corner, and whack the 2x4 with the hammer. Then do the same thing to the side of the corner. Keep soaking and whacking till you seperate the corner leaving it joined to the other side if it is a combo cabinet. For a speaker cabinet, completely remove the top now. Now to seperate the baffle from the sides and bottom, I came up with this method which prevents damage more that many others I've tried. I cut two 2x4s to the inside cab width. I place the amp cabinet face down centered in the middle of a 4x4 foot piece of 3/4 plywood. Next, mark the locations of the 2x4s on the plywood and lift the amp cab off the 2x4s. Using long screws, screw both 2x4s to the plywood. Don't spare the screws either. Place the amp cab back down on the 2x4s as before and screw the Baffle directly to both 2x4s. Again, don't spare the screws. Now with the baffle secured in place, you are free place that small piece of 2x4 on the inside bottom of the cab. You can stand either on the 4x4 plywood, or on the baffle itself and whack the 2x4 with the hammer. Thus directing the force from the hammer blows right to the glue joints of the sides and bottom of the cab. Some more boiling water poured inside along the sides and bottom will softend the glue again as before. Let it soak in, then add a little more. Then, a little more. Don't forget the corners too. You don't want to risk splitting the sides or bottom at the glue joint! Keep in mind,.. "Less Damage Means Less Work later!" Take your time using the hammer and keeping the 2x4 flat inside. Work the hammer blows from the top down the sides to sort a Peel the sides and bottom of the baffle as you work your way around it.. Remember, you want to keep the sides and the bottom connected as one unit. The tolex will help this happen. This makes putting things back together a lot less work. This has been the best method I have come up in my years of Replacing the Fender baffles from the CBS days. Hope this helps. Regards, Rich Koerner, Time Electronics http://home.att.net/~rich-karl/ © Copyright R.K.Koerner 1998 All Rights Reserved. Restoring Grille Cloth From [email protected] Wed Sep 25 15:44:31 CDT 1996 Article: 23411 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntp.primenet.com!enews.sgi.com!news.sgi.com!news.msfc.nasa.gov!newsfeed.internetmci.com!in3.uu.net!prodigy.com!usenet From: [email protected] (Jack Price) Newsgroups: alt.guitar.amps Subject: Re: Grill cloth replacement for Fender Question Date: 25 Sep 1996 06:23:59 GMT Organization: Prodigy Services Company 1-800-PRODIGY Lines: 70 Distribution: world Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: innugap1-int.news.prodigy.com X-Newsreader: Version 1.2 [email protected] (David Taylor) wrote: > >In article <[email protected]>, [email protected] says... >> >>I am getting ready to replace the grill cloth in a "66 Fender >>Super Reverb. How do I do it. Are there any books on the subject >>or is there anyone who has done it and give me some advice >>Thanks in advance >> Randy > >I've done at least a couple dozen myself, and I strongly urge you to have >someone experienced do it. Also, if your current grill cloth is original, >DON'T REMOVE IT. Old, faded and torn grill cloth is still more valuable to >the amp's resale if it's original, rather than new, reissue grill cloth. > >If you must, order a new baffle board and attach the speakers and the new >grill cloth to it, saving the old cloth, still attached to the original >baffle board, for one day if you decide to sell the amp. > > Or..... 1. Remove baffel board and speakers. 2. Remove the 2000 staples, careful not to rip original grill any more. Tuck it away for re-sale. 3. Buy 1 sq yrd of "aged" Black White Silver from Mojo. 4. Have wife, etc help you. 5. Staple one side, I usually do the top. 6. Turn over to the oposite side, have wife pull gently, use a long right angle square laid on the floor to align the silver thread. Then staple. It need not be real tight yet. 7. Then rotate and do a side. Trick here is too pull just hard enough to staple but not too hard, else your lines in the grill will bend and look like sh*t. Must have straight lines!!!!!!!!!!!! 8. Now do the last side. Hard to explain how to do the corners over the net, look how the old one was cornered. 9. I don't use the staple angle that Fender used, but I do use enough staples were the are butted inline right next to each other. 10. Now Tom Bremmer's and Sam Hutton's secret. HEAT my man. Lay board down flat and use a hair dryer and go around the edges slowly. You will see the material tighten from the heat. I'm right handed, so I use my left hand as a guide and it tells me if I'm too close. The real tough part is if the grill gets too hot, it will pull apart with no warning. So take your time, go over and over. Don't put heat on the front face of the cloth, it won't pull evenly, just around the edges. I use a heat gun now on the low setting. But I've f*ck up two jobs up in the last year, by going too fast with too much heat. PS: With grill off, now is a good time to tighten the speaker screws if need be and or re-piant the baffle flat black. Good Luck! Jack A. Price PriceLes$$ Amp Restoration home: 503 641-7146 [email protected] work: 503 613-8116 [email protected] Reverb Amp Effects Loop From no_spam_please@on_a_diet.com Tue Jun 24 00:05:41 CDT 1997 Article: 54053 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!ennfs.eas.asu.edu!nntp.dist.maricopa.edu!usenet From: Dale VanZile Newsgroups: alt.guitar.amps Subject: Re: What's the "best" all around amp to use with a Les Paul Standard? Date: Mon, 23 Jun 1997 14:03:27 -0700 Organization: Maricopa Community Colleges Lines: 71 Message-ID: <33AEE482.7CD8@on_a_diet.com> References: <[email protected]> <[email protected]> Reply-To: no_spam_please@on_a_diet.com NNTP-Posting-Host: mac49.stu-serv-2.sc.maricopa.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Macintosh; I; PPC) Xref: geraldo.cc.utexas.edu alt.guitar.amps:54053 TubeBlastr wrote: > By the way, the amps listed above with the parallel effects loop > aren't my first choice in amps. You could just get a Fender Deluxe > Reverb amp and put a distortion pedal in front of it. This would > give you great sounds in a small room, but it wouldn't take full > advantage of your effects processor because it doesn't have an > effects loop at all. Actually, it does, sort-of. The reverb circuit is in a parallel loop style setup. If you hook a male-RCA->dual-female-RCAs y-cord to the reverb driver output (marked "reverb input") you'll get a nice effects send out of the deal, provided you have the appropriate RCA->1/4" adapter cord. Same deal on the reverb return (or leave the return unhooked if you want to use just the digital reverb/ FX...) and then the reverb knob is now an "effects" knob. Don't unhook the reverb tank from the driver side unless you have a 8-15 ohm/5-10W load resistor to replace it. The reverb driver is a small tube power amp using both halves of a 12AT7 in a parallel singleended configuration. It is transformer coupled, and _will_ blow up if not loaded with something approaching the correct load. > You certainly have a lot of options with $1500 to play with. Another alternative is the Peavey TubeFEX rack preamp/processor, a small used stereo power amp (like a Crown D-75, for example), and either a stereo guitar speaker cab or a pair of 1x12" or 1x15" PA cabinets. The TubeFEX has great sounds for electric guitar, and can also do wonders for an acoustic guitar if played through a full-range speaker setup. Heck, it doesn't sound that bad for acoustic even with guitar speakers. If you use full-range speakers, the TubeFEX has a good cabinet emulator, with several different choices of cab configurations (2x12" open-back, 2x12" closed-back, 4x12", 4x12" "British"). The TubeFEX also has a nice FX loop into which you can plug your old FX processor. The Crown is 40W per side into 8 ohms, or 55W per side into 4 ohms. This should cut it in almost any band, unless you have a really loud drummer. The TubeFEX can be had for around $700 if you have a decent dealer near you, and a used D-75 is about $200. I think Carvin sells a couple different PA cabs that can be had for around $300 each, which fits nicely into your $1500 budget. I have the TubeFEX and a Crown D-75 (as well as a 60W Mk. II-C Boogie combo and a Carvin 4x12" cab), and I'm really happy with the sounds I'm getting from it. I play mostly electric, with a Lone Star Strat and a Hamer Special (with a Duncan JB in the bridge slot). I plug directly into the TubeFEX (via a VOX wah), then put the FX send from the TubeFEX into the Boogie's FX loop return for my 100% dry sound. Then I take the post-MV "preamp-out/power-amp-in" output back into the TubeFEX's FX return and into a Quadraverb 2. These are then mixed into the D-75 and the top two speakers of the 4x12". The Boogie powers the bottom two speakers of the 4x12" as well as its own speaker. One caveat, though: Peavey's customer service/tech support dept. leaves much to be desired. I haven't had any problems, but I had a couple questions which have gone several months unanswered.... Dutch -reply to *****LEGAL NOTICE TO ALL BULK E-MAILERS***** NOTICE TO BULK EMAILERS: Pursuant to US Code, Title 47, Chapter 5, Subchapter II, 227, any and all nonsolicited commercial E-mail sent to this address is subject to a download and archival fee in the amount of $500 US. E-mailing denotes acceptance of these terms. Reverb Fixes From [email protected] Sat Oct 3 13:04:21 CDT 1998 Article: 130128 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!nntp.flash.net!excalibur.flash.net!not-formail From: Danny Russell <*NOSPAM*[email protected]> Newsgroups: alt.guitar.amps Subject: Re: 2 vs 3 spring reverbs ? Date: Sat, 03 Oct 1998 09:33:53 -0700 Organization: ACME Lines: 28 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: p82.sas1.dialup.det1.flash.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win16; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:130128 Tremolux wrote: > > > The only available change is to > >raise the 470 ohm shared Rk to 1k or 1.5k (which it probably should be > >anyway) > > Huh? 470?? The cathode bias resistor on the 12AT7 in my amps is 2.2k! That's > the BF value. > > > then bypass with .22 or .47. > > OK, that will reduce the drive at low frequencies. Yeah, some of the blackface amps did use 2.2k bypassed with a 25/25, but not universally though. Actually on the ones with those values, lotsa times you'll get that snapping, crackling oscillation from the driving 12AT7 when the amp is cranked up. Sounds similar to the O.T. arcing over or on it's way out. I believe that was the reason for the 560pf ceramic connected from plate to cathode on later silverface, supertwin, 75 etc. (frequency-bubble band-aid.) Re-arranging the order of the pin-jumpers cures the problem better (as incorrect order is the source of the problem). Fender has the cathodes tied across first closest to the socket, next the grids are tied across above the jumped cathodes. Lastly the plates are tied together around the outside. The cathode and grid jumpers need to be reversed. (grids together at the bottom, and the cathodes jumpered together above them.) The plates are O.K. around the outside. -Danny Reverb Pan Bottom From [email protected] Fri Nov 22 09:17:29 CST 1996 Article: 28191 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsfeed.internetmci.com!news.webspan.net!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: Different Problem with Fender Reverb Date: 22 Nov 1996 08:05:27 GMT Organization: Netcom Lines: 27 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: den-co14-09.ix.netcom.com X-NETCOM-Date: Fri Nov 22 2:05:27 AM CST 1996 In <[email protected]> Paul Cassone writes: > >This probably sounds weird, but it's true. I have a '68 Princeton >Reverb with no reverb pan cover, so I bought a cover. Problem is, the >reverb doesn't work when the pan is inside the cover -- works fine out of >the cover. I've changed the wires -- same deal. I've placed the pan >differently inside the cover -- same deal. Do do do do (Twilight Zone) > >Any ideas? > >Regards, > >Paul > PAUL!! I've seen this one before. You have to make a cardboard (or Masonite) bottom for the tank...borrow a friend's Fender and take a peek inside the bag to see what it should look like. What is happening is that when you shove the tank into the bag, the fabric is bunching up against the springs, knocking out the tank's ability to do its thing. Making a bottom for the tank will stop this from happening. Lord Valve [email protected] (Fat Willie) From [email protected] Fri Nov 22 09:18:03 CST 1996 Article: 28210 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newspump.sol.net!ddsw1!news.mcs.net!usenet From: "Teleologist" Newsgroups: alt.guitar.amps Subject: Re: Different Problem with Fender Reverb Date: 22 Nov 1996 12:33:12 GMT Organization: MCSNet Services Lines: 21 Message-ID: <01bbd871$d3858e70$610258aa@alsnt> References: <[email protected]> <[email protected]> NNTP-Posting-Host: 205.253.42.11 X-Newsreader: Microsoft Internet News 4.70.1155 Lord Valve wrote in article <[email protected]>... > In <[email protected]> Paul Cassone > writes: >> > >This probably sounds weird, but it's true. I have a '68 Princeton > >Reverb with no reverb pan cover, so I bought a cover. Problem is, the > > >reverb doesn't work when the pan is inside the cover > PAUL!! I've seen this one before. You have to make a cardboard (or > Masonite) bottom for the tank...borrow a friend's Fender and take a > peek inside the bag to see what it should look like. While you're at it - I cover the top side of the cardboard with a layer of heavy aluminum foil, stick the pan to the bottom with a couple of pieces of thick double sided foam tape, and connect the foil to the pan's shell with a piece of wire. This keeps the pan from sliding around & isolates it somewhat from floor vibration. Not sure if the shielding really matters read somewhere that the coils are humbucking? - but it can't hurt! :) Reverb Trans Specs From [email protected] Fri Oct 24 18:53:31 CDT 1997 Article: 68343 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!www.nntp.primenet.com!globalcenter1!news.primenet.com!nntp.primenet.com!news.maxwell.syr.edu!news.monmouth.com!nntp.flash.net!excalibur.flash.net!notfor-mail From: Danny Russell Newsgroups: alt.guitar.amps Subject: Re: Fender Reverb X-former specs or source Date: Thu, 23 Oct 1997 18:57:22 -0700 Organization: ACME Lines: 18 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: detasc15-241.flash.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win16; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:68343 Andy Cowley wrote: > > Has anyone got any idea of the specs for a Fender reverb transformer. > I presume that it matches impedance from the 12AXwhatever to the > (presumably) low impedance of the tank, so it's a baby S/E output > transformer. I'm scratch building so I need a source or better > a spec - just the turns ratio would be fine or even the input > impedance of the tank. > > My guess is 10-20k in and a few to a few tens of ohms outm> about a 30:1 turns ratio. Am I close? > > Andy Cowley 22k ohms primary:8 ohms secondary. Also the drive is handled by one entire 12AT7 (both halves paralleled). -Danny Reverb Unit Mods Page From [email protected] Wed Jul 14 23:29:39 CDT 1999 Article: 189733 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!nntp.abs.net!newshub2.home.com!news.home.com!news.rdc1.il.home.com.POSTED!notfor-mail Message-ID: <[email protected]> From: Tom Kochie X-Mailer: Mozilla 4.51 [en] (Win98; I) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: alt.guitar.amps Subject: Re: Reissue Reverb Unit Mods References: <[email protected]> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 16 Date: Thu, 15 Jul 1999 03:08:26 GMT NNTP-Posting-Host: 24.6.1.165 X-Complaints-To: [email protected] X-Trace: news.rdc1.il.home.com 932008106 24.6.1.165 (Wed, 14 Jul 1999 20:08:26 PDT) NNTP-Posting-Date: Wed, 14 Jul 1999 20:08:26 PDT Organization: @Home Network Xref: geraldo.cc.utexas.edu alt.guitar.amps:189733 Eric, Check out this link.... http://www.persci.com/~larrysb/reverb.html Good luck, Tom Eric Erickson wrote: > I am going to purchase a reissue Fender Reverb Unit. What can be done to > these to make them sound better? I know the a common mod is to replace the > 6V6 with a 6K6 but is there anything else? > > Regards, > Eric Erickson Rivera Designed Fenders From [email protected] Thu Apr 9 13:53:15 CDT 1998 Article: 96733 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!www.nntp.primenet.com!globalcenter0!news.primenet.com!news.primenet.com!notfor-mail From: [email protected] (Gil Ayan) Newsgroups: alt.guitar.amps Subject: Re: Fender Twin Reverb II Date: 7 Apr 1998 13:25:01 -0700 Organization: Ayan Enterprises Lines: 53 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> X-Posted-By: @138.13.115.17 (urula) X-Newsreader: WinVN 0.99.8 (x86 32bit) MIME-Version: 1.0 Content-Type: Text/Plain; charset=US-ASCII Xref: geraldo.cc.utexas.edu alt.guitar.amps:96733 In article <[email protected]>, [email protected] Tremolux says: > >>Then just as I was >>flooring the accelerator to get there before someone else did, he said "It's >>a Twin Reverb II." > >Hit the brake!!! These things have the most dull and lifeless clean tone that >you can imagine. As bad as a Mesa Boogie. These Rivera-designed amps were never received with warm affection, and I still wonder why. However, there are several things to be noted: 1. These amps are point-to-point wired and their clean channel circuitry -- looking at is as we speak -- can be turned into a Blackface one by removing the 0.001 uF cap (plate to cathode) on V1, and changing the feedback network (6 resistors total). 2. In addition to the above, you get a buffered FX loop and good reverb. If you don't like the presence of the FX loop, it takes 2 minutes to take it out of the circuitry. The amp has 6 12AX7 tubes, plenty to do anything you want out of an amp. 3. These amps' lead channel design is about as close to an old Dumble that ever came into production, incorporating a 500 pF plate-to-cathode feedback in V2A and a large coupling capacitor (0.0047 uF, to be exact) after the 1st OD stage to mitigate the typical Fender fartiness -- though Dumble used a variation of that scheme. 4. Tremo and I both know Jay Graydon and know what he likes and doesn't like. Jay once told me that Larry Carlton used to have a Twin II in the early 80s that sounded as good as his (Larry's, not Jay's) Dumble. 5. I have repeatedly heard people talk down on the Concert amps of the same vintage, and I have always found them to ge great amps if properly dialed in, and provided you have the right touch for them. In the words of Paul Rivera, "all of those amps are great platforms to do just about everything you want with them. Point to point, cheap and they have a good sound of their own: they're one heck of a deal." I do agree. For those whose only concept of a guitar tone is to plug into a 60s Blackface, co be it; for those into something a little different with more choices, do consider these ealry 80s Fenders. Gil -______ __ __ ______ __ __ / __ / / /_/ / / __ / / \/ / Gil Ayan, Los Angeles, CA / /_/ / \__ / / /_/ / / / / / Email: [email protected] /_/ /_/ /_/ /_/ /_/ /_/\__/ http://home.earthlink.net/~ayan SF Deluxe Reverb Questions From [email protected] Sun Nov 1 23:00:01 CST 1998 Article: 136270 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!novia!sequencer.newscene.com!not-formail From: [email protected] (Ned Carlson) Newsgroups: alt.guitar.amps Subject: Re: Deluxe Reverb-'70/'71 Several Questions Part II Date: 1 Nov 1998 00:07:01 -0600 Organization: Triode Electronics Lines: 176 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] X-Newsreader: Forte Free Agent 1.11/32.235 Xref: geraldo.cc.utexas.edu alt.guitar.amps:136270 On Sun, 01 Nov 1998 01:55:40 GMT, [email protected] (JJman) wrote: >2) The SS recifier is not a good idea (too much voltage). How >about a GZ34? How many more volts will it put out over the stock >5U4GB? Not as much as you'd think, maybe 10-15 volts or so, because a Deluxe Reverb doesn't pull much current thru the rectifier tube. See the chart at http://www.triodeel.com/5ar4_p4.gif > beleive the GZ34 actaully pulls fewer amps from the power >trans and was stock on the BFDR. I am not a big fan of major sag so I >may want an option if I need it. Part of the problem is that NOS GZ34 are expensive. Chinese ones..which we sell 'cause no one (HEY! Svetlana! Tesla! You listening?) wants to make new, decent GZ34, are useable but mainly 'cause a Deluxe only draws around 70 ma at idle. (GZ34 are rated for 250 ma max). But there's other, better solutions: 5V4-G/GA: Good US ones aren't too common, but aren't too expensive, either. Sovtek makes one that's apparently good enough for Matchless. It has a heater cathode like a 5AR4 & drops less voltage than 5U4. The current draw of a Deluxe is within spec for these tubes. Used GZ34's: Good old GZ34 normally outlast the power tubes by a bunch, but often people replace the GZ34 anyway, even tho it's still got lotsa life left, so there's a few floating around for much cheaper than new. CV378/GZ37: Looks like a tall, beefed up version of GZ34. Sort of halfway between 5U4 and GZ34. They're rated for 350 ma max, so ought to last eons in a Deluxe. Available >from us or Angela for about $20, NOS. Either way you cut it, I'd up the voltage rating of the filter caps to 500V from 450. Considering normal parts tolerances, and variation in line voltages, that's probably a good idea anyway, but adding another 10 or 15V to the power supply makes it even more likely the voltage will go over the ratings...you do not want to blow up your filter capacitors. It ain't a pretty sight. While you're at it, replace that bias supply cap if someone hasn't done that already. Cheap insurance. Then, if you do decide to use one of the lower voltage drop rectifiers, go back and readjust the bias. Now, guaranteed, somebody's gonna say that the voltage is gonna be too high for a 6V6.Book says so, right? I say that if you've got *good* 6V6-GT or 6V6-GTA, and make sure the bias is right...25 ma sounds about right, with 435V,that's derating the plate dissipation by about 20%...OK. Actually, I've tested 6V6-GT's in amps running up to 460V...this *may* sound insane, but take a look at some other similarly sized tubes..like 7591-A, which is rated for 550V, or 2E26 which is rated for 600V. OK, 7591A IS kind of an insane tube, anyway. I'd say stay away from Chinese or Russian 6V6, I doubt they'll last long enough for you to get the bias set. > >3) Pre-amp tube sheilds-WAZZUP? I've read that these rob tone. Maybe someone was using Dr Stereo's "Tone Swine Special", tone-sink tube shields? I can't imagine how this could be true, but perhaps someone could enlighten me, I mean , if someone can hear it, I believe them, but I'd sure like to hear why that might be true...after all, I don't play a guitar, so obviously I don't know shit about this anyway. I will say, if the reason for this observed effect has to do with the tube shield retaining heat, then, yes, there may be something to it. Believe it or not, the military *did* (I bet Lord Valve has seen some) use heat sinking black tube shields, with little phosphor bronze accordion thingies to sink heat away from the glass. I shit you not, they're called IERC shields, and the military really *did* do a study that showed that tube life could be measurably extended by using them. (The military, unfortunately, did not do any Tone Studies. I guess Col. Tone Hog had been decommisioned) I suppose one *could* emulate this by painting one's tube shields black, then stuffing some aluminum foil in there to increase the metal to glass contact. >4) I know how to bias by installing 1 ohm resistors on the >cathodes but please explain the "transformer shunt method." Hook one lead to the transformer center tap, the other to *one* of the tubes at Pin 3. Turn on the amp, let it get nice & warm, turn on the standby.Read meter, adjust bias, then turn the POWER switch off, not the standby (this will let the tubes drain off most of the B+ while cooling down). Then wait for a minute or two. Switch the lead to pin 3 of the other 6V6. Turn the standby off, then turn the power on. Again, let 'er warm up then hit the standby. Read the other side. If the tubes are properly matched, the reading will be within 2 ma of the other side. >I do have a high quality meter (Fluke 21) I've got an IBM meter made by Fluke, and it never works for this. (I dunno why. Of course, I don't play guitar, so I can't be expected to know shit about these things) I use a godawful antique Simpson 260. (This earns me a honorary Dr Stereo flame) >and I know to switch the red >wire to the milliamps prong for this method. I guess all I need to >know is where to put each connection? ( I am very aware of the lethal >voltages and where they are.) It will read the actual idle >current-no? The plate current. Reading the cathode gives you plate AND screen current together. The screen accounts for roughly 2 ma. >ill it show me the total of both power tubes? No, just the one you are checking. >6) Tone robbing grid>ground caps. Schem shows 1200pf. >Mine are .001u (=1000pf close enough). Has anyone ever tried a lower >value cap to avoid oscillation yet preserve tone? After all isn't >this oscillation "ultra sonic" (very high frequency) and wouldn't a >lower value cap increase tone while still eliminating >oscillation? So far, I don't recall anyone on this NG relating any horror stories about what happened when they just snipped out those grid-resistor bypass caps. If there are any, I'd like to hear 'em. >From what I've seen, amp manufacturers will do stuff like drop those caps in, even if only a tiny fraction of the amplifiers they made had some kind of oscillation problem, even if it only happened under certain rare conditions, (say , for example, it only happened with a certain combination of tubes & speakers) probably because engineers hate getting called on the carpet for that kind of shit.. I suspect that the problem was Fender buying cheaper output xfmrs.. But OTOH, I have seen Fenders that only oscillated *without a load*. This is going to be very rare for the average person to see, because old Fenders have shorting output jacks. However, here's a totally unscientific wild ass guess: Say people were using combo to play cabinets instead, or people with heads, either way, accidentally left the speaker end of the cable disconnected..dumb, but it could happen..and the tubes melted down due to oscillation. Customers bitch to dealers, dealers bitch to reps, reps bitch to management, management bitches to engineering. Engineering stuffs in 1200 pf caps to get 'em all to shut up & quit bitching. A Rube Goldberg scenario, but the electronics industry is full of Rube Goldberg scenarios. Hell, let's talk about Windows 98.. The problem with the oscillation, is that the easiest ways to detect it, is seeing it on a 'scope (which most folks don't have), or watching your tube plates turn red as a beet. There may be.. I'm sure there is..audible effects, too, *if* the speaker's plugged in when it's oscillating, and you're playing thru it. Ned Carlson Triode Electronics "where da tubes are!" 2225 W Roscoe Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun http://www.triodeel.com Your Start Page for Tube and Tube Amp info on the net... http://www.triodeel.com/tlinks.htm From [email protected] Sun Nov 1 23:02:31 CST 1998 Article: 136311 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: Deluxe Reverb-'70/'71 Several Questions Part II Date: 1 Nov 1998 09:49:05 GMT Organization: ICGNetcom Lines: 180 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: den-co55-05.ix.netcom.com X-NETCOM-Date: Sun Nov 01 3:49:05 AM CST 1998 Xref: geraldo.cc.utexas.edu alt.guitar.amps:136311 In <[email protected]> [email protected] (Ned Carlson) writes: > >On Sun, 01 Nov 1998 01:55:40 GMT, [email protected] (JJman) wrote: (snip) >Part of the problem is that NOS GZ34 are expensive. Chinese >ones..which we sell 'cause no one (HEY! Svetlana! Tesla! You >listening?) wants to make new, decent GZ34, are useable but mainly >'cause a Deluxe only draws around 70 ma at idle. (GZ34 are rated >for 250 ma max). >But there's other, better solutions: LV: The Chinese aren't that bad. The Sovteks were better, but they're really hard to find now. >5V4-G/GA: Good US ones aren't too common, but aren't too expensive, >either. Sovtek makes one that's apparently good enough for Matchless. >It has a heater cathode like a 5AR4 & drops less voltage than >5U4. The current draw of a Deluxe is within spec for these tubes. LV: I've used the Sovtek, too. It's good. > >Either way you cut it, I'd up the voltage rating of the filter caps >to 500V from 450. Considering normal parts tolerances, >and variation in line voltages, that's probably a good idea anyway, >but adding another 10 or 15V to the power supply makes it even >more likely the voltage will go over the ratings...you do not want to >blow up your filter capacitors. It ain't a pretty sight. >While you're at it, replace that bias supply cap if someone hasn't >done that already. Cheap insurance. LV: Use a bigger value for the bias cap, at least double the capacitance of the original. You'd be surprised how much hum is due to bias ripple. As for voltage, I'd go for twice whatever the bias is...100V for 50-volt range, etc. > >Then, if you do decide to use one of the lower voltage drop >rectifiers, go back and readjust the bias. > >Now, guaranteed, somebody's gonna say that the voltage >is gonna be too high for a 6V6.Book says so, right? >I say that if you've got *good* 6V6-GT or 6V6-GTA, >and make sure the bias is right...25 ma sounds about right, with >435V,that's derating the plate dissipation by about 20%...OK. >Actually, I've tested 6V6-GT's in amps running >up to 460V...this *may* sound insane, but take a look at some other >similarly sized tubes..like 7591-A, which is rated for 550V, >or 2E26 which is rated for 600V. OK, 7591A IS kind of >an insane tube, anyway. >I'd say stay away from Chinese or Russian 6V6, I doubt they'll >last long enough for you to get the bias set. LV: If you use the Chinese 6V6s, wear goggles so you don't get any glass in your eyes when they explode. The Sovteks are only slightly better. ANY 6V6 will benefit from changing the screen resistor to 1K/5W, however. > >> >>3) Pre-amp tube sheilds-WAZZUP? I've read that these rob tone. > >Maybe someone was using Dr Stereo's "Tone Swine Special", >tone-sink tube shields? > >I can't imagine how this could be true, but perhaps someone could >enlighten me, I mean , if someone can hear it, I believe them, >but I'd sure like to hear why that might be true...after all, I >don't play a guitar, so obviously I don't know shit about this >anyway. LV: I read something about capacitance from the shields causing HF rolloff, but I can't see how it could be significant at any frequency within the passband of a typical guitar rig. Most guitar speakers crap out around 6KHz, and that's gotta be way lower than anything a tube shield would dump. > >I will say, if the reason for this observed effect has to do with >the tube shield retaining heat, then, yes, there may be something to >it. Believe it or not, the military *did* (I bet Lord Valve has seen >some) use heat sinking black tube shields, with little phosphor >bronze accordion thingies to sink heat away from the glass. >I shit you not, they're called IERC shields, and the military really >*did* do a study that showed that tube life could be measurably >extended by using them. (The military, unfortunately, did not >do any Tone Studies. I guess Col. Tone Hog had been decommisioned) >I suppose one *could* emulate this by painting one's tube shields >black, then stuffing some aluminum foil in there to increase the >metal to glass contact. LV: Yeah, I've seen those...I have a pile of 'em, in fact. They are pretty hard to remove if they've been on for a long time, though. > >>4) I know how to bias by installing 1 ohm resistors on the >>cathodes but please explain the "transformer shunt method." > >Hook one lead to the transformer center tap, the other to >*one* of the tubes at Pin 3. Turn on the amp, let it get nice & warm, >turn on the standby.Read meter, adjust bias, then turn the POWER >switch off, not the standby (this will let the tubes drain off most of > >the B+ while cooling down). Then wait for a minute or two. >Switch the lead to pin 3 of the other 6V6. Turn the standby off, >then turn the power on. Again, let 'er warm up then hit the standby. >Read the other side. If the tubes are properly matched, the reading >will be within 2 ma of the other side. LV: This is the candy-ass method for newbies. You'd do well to follow Ned's advice, since once the meter is connected to the center-tap, the other probe will become live with the meter set to a current range. Myself, I enjoy the sparks... > >>I do have a high quality meter (Fluke 21) > >I've got an IBM meter made by Fluke, and it never works >for this. (I dunno why. Of course, I don't play guitar, so I >can't be expected to know shit about these things) >I use a godawful antique Simpson 260. >(This earns me a honorary Dr Stereo flame) LV: No problems with my Fluke bench meter. 8050A, I believe it is. > >>and I know to switch the red >>wire to the milliamps prong for this method. I guess all I need to >>know is where to put each connection? ( I am very aware of the lethal >>voltages and where they are.) It will read the actual idle >>current-no? > >The plate current. Reading the cathode gives you plate AND >screen current together. The screen accounts for roughly 2 ma. LV: I like the cathode resistor method...it's less scary, and it'll result in a more conservative setting. I think it's the way to go for hobbyists and newbies. > >>ill it show me the total of both power tubes? > >No, just the one you are checking. > >>6) Tone robbing grid>ground caps. Schem shows 1200pf. >>Mine are .001u (=1000pf close enough). Has anyone ever tried a lower >>value cap to avoid oscillation yet preserve tone? After all isn't >>this oscillation "ultra sonic" (very high frequency) and wouldn't a >>lower value cap increase tone while still eliminating >>oscillation? > >So far, I don't recall anyone on this NG relating any >horror stories about what happened when they just snipped >out those grid-resistor bypass caps. >If there are any, I'd like to hear 'em. LV: I just cut 'em off. Never had a problem yet. > >(snip) >The problem with the oscillation, is that the easiest ways to detect >it, is seeing it on a 'scope (which most folks don't have), or >watching your tube plates turn red as a beet. There may be.. >I'm sure there is..audible effects, too, *if* the speaker's >plugged in when it's oscillating, and you're playing thru it. LV: You can use a dog (or cat) and a piezo-tweeter. (You can get a piezo from any Radio Shack.) Leave your speaker hooked up, and put the piezo-tweeter in parallel with the output; point it at Fido (or Garfield). If he/she takes a powder, your shit be oscillatin'. (This might sound wierd, but I guarantee you it works.) Lord Valve Visit my website: http://www.freeyellow.com/members2/lord-valve/ Good tube FAQ for newbies. Click the e-mail link and request a tube catalog. I specialize in top quality HAND-SELECTED NOS and current-production vacuum tubes. Good prices, fast service. TONS of gear and parts in stock...let's DEAL! "If you voted for Clinton in the last election, you can't take a dump here. Your asshole is in Washington." (Seen on the men's room wall, Outback Steakhouse, Tacoma,Washington) > > > >Ned Carlson Triode Electronics "where da tubes are!" >2225 W Roscoe Chicago, IL, 60618 USA >ph 773-871-7459 fax 773-871-7938 >12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun >http://www.triodeel.com >Your Start Page for Tube and Tube Amp info on the net... >http://www.triodeel.com/tlinks.htm > From [email protected] Sun Nov 1 23:02:44 CST 1998 Article: 136359 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!howland.erols.net!news.maxwell.syr.edu!nntp2.dejanews.com!nnrp1.dejanews.com!not-for-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Deluxe Reverb-'70/'71 Several Questions Part II Date: Sun, 01 Nov 1998 15:47:26 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 20 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: 206.30.143.101 X-Article-Creation-Date: Sun Nov 01 15:47:26 1998 GMT X-Http-User-Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows 95) X-Http-Proxy: 1.1 x12.dejanews.com:80 (Squid/1.1.22) for client 206.30.143.101 Xref: geraldo.cc.utexas.edu alt.guitar.amps:136359 In article <[email protected]>, [email protected] wrote: [snip..] > > So far, I don't recall anyone on this NG relating any > horror stories about what happened when they just snipped > out those grid-resistor bypass caps. > If there are any, I'd like to hear 'em. Ask and you shall receive. I cut them out of my '70 DR and suddenly found out exactly what they were used to suppress. It was like a crappy fuzz pedal was mixed into my dry signal. Sounded awful. I know it was the caps since I then put them back in and it went away. I ended up redoing the lead dress (what a pain) in order to get rid of the problem for good. WP -----------== Posted via Deja News, The Discussion Network ==---------http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own SF Deluxe mods From [email protected] Wed Oct 2 19:09:23 CDT 1996 Article: 23962 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newspeer.gsl.net!news.gsl.net!portc01.blue.aol.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (LarrySB) Newsgroups: alt.guitar.amps Subject: Re: SF Deluxe Reverb mods? Date: 2 Oct 1996 14:40:58 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 63 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (LarrySB) NNTP-Posting-Host: newsbf02.mail.aol.com << Would there be any reason to skip this particular amp and wait for an early 70's model to pop up? >> I don't think so, I happen to own one myself. The DR is one of the few to escape most of the horseshit design changes Fender did in the 70's. I bought a bone stock 78 DR (even the tubes were original) for about what you've been offered. It's real clean and works great. I did do a blackface conversion on it, and removed the "pull for boost" nonsense. I also had to change the reverb pan. The late 70's DR can be blackfaced easily with two exceptions. The B+ voltage will still be a little too high; and the wiring quality utterly sucks compared to the ones from the 60's. What you do is this: Remove the suppresion caps from the 6V6 sockets (1200pf discs) Revert the phase inverter schematic to the 65 circuit (just a few resistor value changes) Revert the reverb drive 12AT7 circuit to the blackface circuit Remove all the wiring associated with the boost switch and pedal Optionally change the power supply divider resistors to get the preamp and phase invertor supplies to lower voltages. (I actually preffered the Silverface values myself) Option but recommend: rewire at least the output stages with short, neat runs of wire, using the pictorial layouts from the early designs. You can find a suitable layout in the Groove Tube book or Weber's book. optional: if you find the voltages more than 10% higher than on the BF schematic, you can lower them neatly and easily by installing a stud mount Zener (cathode case) between the power xfrmr center tap and the chassis ground. Use a voltage that will drop the B+ by the desired amount, usually around 20-30 volts. You can also change the power xfrmer or add a bucking xfrmr, but the Zener diode is clean, cheap, easy and reversable. For tubes, I really like NOS Sylvania 6V6GTA the best. Current Russian ones will almost certainly self destruct in a matter of minutes. Even NOS 6V6 will sometime arc or carry on. Bias around 25ma per output tube. Since I had to replace my reverb spring, I went with a 3 spring replacement. The reverb is super lush now, sounds like a big church! I still haven't found the perfect speaker, but the stock '78 unit is pretty decent. If you like to work on amps yourself, a 78 can be a bargain. But if you are relying on a tech to do it for you, ask his opionion first. The poor quality of wiring is enough to make most techs charge a little more for the conversion. -Dr. Nuketopia Technology Director of the World-Wide Monetary Conspiracy All opinions strictly reflect the party line. Read the Blue Glow in Tubes FAQ at http://www.persci.com/~larrysb ****************************** Please, no unsolicited e-mail. SF Reverb Cathode Resistor From [email protected] Tue Jun 3 11:58:06 CDT 1997 Article: 51836 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!ix.netcom.com!news From: [email protected](Lord Valve) Newsgroups: alt.guitar.amps Subject: Re: Problems with my '68 Super Date: 3 Jun 1997 06:26:21 GMT Organization: Netcom Lines: 15 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: den-co9-22.ix.netcom.com X-NETCOM-Date: Tue Jun 03 1:26:21 AM CDT 1997 Xref: geraldo.cc.utexas.edu alt.guitar.amps:51836 In <[email protected]> [email protected] (AXEIST) writes: (weird stuff snipped) Lord Valve Speaketh: I think I posted on this before...but I'll give it another shot. Many SF Super Reverbs had a 470 ohm cathode resistor installed on the reverb drive tube, with no bypass cap. Change the 470 ohm to a 1.5K or 2.2K 1-watt metalfilm. The 470 ohm value runs the tube WAY hot; some of the NOS 12AT7s can survive like that for awhile, but if you put one of those Chinese 12AT7s in there, it'll die pronto. Those popping noises you're hearing are probably the sound of the reverb drive tube burning itself to a crisp. Lord Valve SF Vibrolux Changes From [email protected] Fri Apr 25 23:40:43 CDT 1997 Article: 47089 of alt.guitar.amps From: [email protected] (Bill Bolton) Newsgroups: alt.guitar.amps Subject: Re: 6L6GTA Bias in SF VR?? Date: Fri, 25 Apr 1997 23:55:36 GMT Reply-To: [email protected] Message-ID: <[email protected]> References: <[email protected]> X-Newsreader: Forte Agent 1.01/32.393 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 139.134.92.44 Lines: 29 Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!newsfeeds.sol.net!europa.clark.net!newsfeed2!news.telstra.net!139.134.5.33! Xref: geraldo.cc.utexas.edu alt.guitar.amps:47089 [email protected] (Simply Steve) wrote: > And I am still looking for a schematic for it. The one Lee was kind > enough to fax me (for free!) is, alas, unreadable. Specific Vibrolux Reverb schematic differences I have found by observation between between the SF AA270 schematic and a '81 Blackface II are: 1. Voltage on centre tap of OT = 451V 2. 2K2 decoupling resistor in B+ after choke instead of 4K7 3. 330K resistors on phase splitter grids instead of 1M 4. 680R resistor of phase splitter cathodes instead of 470R 5. 2000pf cap across the 220K grid resistor on the reverb return 6. The volume boost stuff, adds a 10K resistor between the ground end of the 220K on the grid to the driver tube. A 1K resistor connects to this junction of the 10K and 220K and goes to the pull boost switch. The other side of the pull boost switch goes to the secondary of the reverb OT. A footswitch, which shorts to ground, also connects to the junction of the 10K and 220K resistors. 7. 100K1W pre-amp late resistors in place of 1/2W 8. Miscellaneous measurements at idle after cap replacement: After 2K2 decoupler = 422V After 10K decoupler = 356V Junction of diode and 50uF in bias supply = 56V Centre tap of bias balace pot = 45V Grids of 6L6 = 41V Bias current = 31ma Cheers, Bill Bill Bolton [email protected] Sydney, Australia Scrape Vibrato Pot From [email protected] Wed Feb 5 11:04:46 CST 1997 Article: 37347 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!www.nntp.primenet.com!nntp.primenet.com!news.sprintlink.net!newspeer.sprintlink.net!howland.erols.net!panix!news.panix.com!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Vibrato pot with switch (was GP's "MODZILLA" mods?) Date: 5 Feb 1997 02:20:55 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 72 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> In <[email protected]> [email protected] (Phillip C. Saunders) writes: >Hoffman Electronics in Florida carries a pot that works for this mod, >but when I spoke to him about it he said the taper isn't quite right for >the Vibrato Intensity switch. It worked, but many people who did the >mod didn't like the feel and reinstalled the original. I didn't follow the start of this thread, but I assume it's talking about the loading effect of the 50k reverse-log vibrato pot. I've mentioned in the past that the pot can load the plate circuit of the previous tube (Weber got this right! ). Many people disconnect the intensity pot, or try to install switches or whatever. Finding a reverse log pot with a built-in switch is almost impossible. In fact, finding other values of reverse log pots is pretty tough (using a 100k rev. log pot would be a an OK solution if you could find one). BUT...here's an idea: You can find 50k reverse log replacement pots pretty easily--from Mojo or Smart Parts in Chicago. It should be possible to 'score' one end of the carbon element (in a replacement part...not in your original black-face pot) so that the wiper goes open at one end. In other words, you'd have to open up the pot and use an Exacto knife to carefully slit the carbon on the *counter-clockwise* (CCW) end of the pot. As you turn the pot CCW, the wiper will go past the opencircuited end of the carbon element. This will remove the pot from the circuit. There you are. Expect a few db volume boost when the pot is at full CCW. That's what this is about, right? A slight increase in volume is usually perceived as 'better' tone, but don't let this throw you. In fact, I'm not saying this is better than just turning up the volume a tad. I'm offering it as a better alternative for those who were recently talking about drilling holes for switches or trying to find RA pots with switches. This sorta does the same thing, but without the click-detent. This same trick works for taking the tone control out-of-circuit on a guitar so it doesn't load the pickups. I just realized that it should be a relatively non-intrusive way of doing the same for the vibrato control. A couple things: I'm talking about the 50k RA (reverse log) vibrato intensity control, NOT the speed control. Do this with a replacement part. You will have to take it apart, and you may mess it up if you're not careful. Turn the pot CCW and watch the wiper to make sure you've got the correct end. Use an ohmmeter to make sure that you've opened the carbon. Solder a resistor (around 200k to 500k) across the two 'active' terminals of the pot. This will keep the couping caps at ground potential, and will avoid possible 'popping' sounds as the control is turned 'on'. Don't put that thing on the couch. It's filthy. If you didn't understand the post, ask before trying it. Now paste a poodle on my head and call me Gerald! MGarvin From [email protected] Wed Feb 5 11:05:01 CST 1997 Article: 37368 of alt.guitar.amps Path: geraldo.cc.utexas.edu!arlut.utexas.edu!news.eden.com!matrix.eden.com!keen From: [email protected] (R.G. Keen) Newsgroups: alt.guitar.amps Subject: Re: Vibrato pot with switch (was GP's "MODZILLA" mods?) Date: 5 Feb 1997 13:31:04 GMT Organization: Adhesive Media, Inc. Lines: 13 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: matrix.eden.com X-Newsreader: TIN [version 1.2 PL2] Mark Garvin ([email protected]) wrote: : BUT...here's an idea: : You can find 50k reverse log replacement pots pretty easily--from Mojo : or Smart Parts in Chicago. It should be possible to 'score' one end : of the carbon element (in a replacement part...not in your original : black-face pot) so that the wiper goes open at one end. In other : words, you'd have to open up the pot and use an Exacto knife to : carefully slit the carbon on the *counter-clockwise* (CCW) end of the : pot. As you turn the pot CCW, the wiper will go past the open: circuited end of the carbon element. This will remove the pot from : the circuit. There you are. I might try coating one end with a thin layer of epoxy, same result. Screen Resistors From [email protected] Mon Nov 11 20:44:49 CST 1996 Article: 27182 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!panix!news.panix.com!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: Princeton & screen resistors Date: 11 Nov 1996 20:14:03 -0500 Organization: PANIX Public Access Internet and Unix, NYC Lines: 24 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: panix2.panix.com >LC Krakowka wrote: >> >> The Princeton Reverb schematic doesn't show any 470 ohm 1 watt screen >> resistors. Would it be wise to add them? My amp's an AB1270 circuit as far >> as I can tell. TIA In <[email protected]> Brad & Dona Bolton writes: >Yes, indeed, add them. And make sure you use the 1-watters or better. >This will prolong tube life and tighten up the sound some. The louder >you play your amp, the more screen current flows, and teh more you need >those resistors. Correct, and I kinda like the adjective 'tighten' cause the screen resistors do contribute some negative feedback. I used to use higher wattage resistors sometimes, but I've been sticking to 1-watters cause they'll act like a fuse if something goes wrong. Here is another place where carbon comps can react differently >from carb or metal films: they're much better at handling transient over-wattage conditions. Unfortunately, I've seen them get lower in value sometimes...not good for a screen resistor to do this. MGarvin NYC Shielding Plate Problems From [email protected] Sun Feb 7 16:16:33 CST 1999 Article: 157502 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!news-feed1.tiac.net!cam-newshub1.bbnplanet.com!news.gtei.net!newscon02!prodigy.com!not-for-mail From: "LORD VALVE" Newsgroups: alt.guitar.amps Subject: Re: Weird problem with silverface twin Date: Sun, 7 Feb 1999 01:55:06 -0700 Organization: Prodigy Services, Inc Lines: 51 Message-ID: <[email protected]> References: NNTP-Posting-Host: dnvrb103-38.splitrock.net X-Trace: newssvr03-int.news.prodigy.com 918377709 3464983 209.156.134.84 (7 Feb 1999 08:55:09 GMT) X-Complaints-To: [email protected] NNTP-Posting-Date: 7 Feb 1999 08:55:09 GMT X-Newsreader: Microsoft Outlook Express 4.72.3155.0 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3155.0 Xref: geraldo.cc.utexas.edu alt.guitar.amps:157502 Robert Orr wrote in message ... >I replaced the 100K plate resistors in my twin, changed the slope resistor >to 56K, put in a lower value cap on the bright switch. The amp sounds >great OUT OF THE CABINET. BUT...... when I put it in the cabinet, some >weird grounding thing causes the amp to howl uncontrolably. This happens >when the amp is totally in contact with the sheild on the inside of the >cabinet. AND... when it is only partially in contact, (just sitting in >the cabinet, not held in with the bolts) I can plug in my guitar and make >the amp "go to 10" with the volume all the way off on the amp. This is >triggered just by plugging a cable into the input jack. (I only use the >vibrato channel, the normal channel is disabled) >Its as if plugging in the cable causes the volume control on the amp to >short out. Also, when I turn the volume control on my guitar down, the amp >gets more and more hum. > >None of these symtoms are present when the amp is not in physical contact >with the cabinet. > >Anybody got any sugesstions as to what would be causing this weird behavior? > >Thanks, > >Robert Lord Valve Speaketh: If the shield is the old window-screen type, make sure that none of the little wires from it are poking down into the amp chassis... those can play hell with anything they touch inside. If you have the aluminum plate type, check to make sure none of the internal parts are sticking up far enough to touch the plate. The easiest way to do this is to put a ruler across the top of the chassis and slide it back and forth over the whole length of the amp...if anything touches the ruler, push it down. Lord Valve Visit my website: http://www.freeyellow.com/members2/lord-valve/ Good tube FAQ for newbies. Click the e-mail link and join my SPAM LIST; just put "SPAM ME" in the header and I'll sign you up. (If you only want a set of e-mail catalogs, put "CATS ONLY" in the header.) I specialize in top quality HAND-SELECTED NOS and current-production vacuum tubes for guitar and bass amps. Good prices, fast service. TONS of gear and parts in stock...let's DEAL! NOW ACCEPTING VISA, MASTERCARD, AND DISCOVER! "Ninety percent of everything is CRAP." - Sturgeon's Law Showman vs Twin From [email protected] Sun Dec 3 10:51:40 CST 1995 Article: 72928 of rec.music.makers.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (TimTube) Newsgroups: rec.music.makers.marketplace,rec.music.makers.guitar Subject: Re: FS: 1966 Fender Twin (head) Date: 3 Dec 1995 09:39:01 -0500 Organization: America Online, Inc. (1-800-827-6364) Lines: 11 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (TimTube) NNTP-Posting-Host: newsbf02.mail.aol.com Xref: geraldo.cc.utexas.edu rec.music.makers.marketplace:43020 rec.music.makers.guitar:72928 Mark, You're right black face Dual Showmans were different for Twin Reverbs, they lacked the reverb and a gain stage (the second half of the reverb recovery tube). It was the silver face Dual Showman Reverbs that had the same chassis and circuitry as a silverface Twin Reverb and a Quad Reverb. Super Sixs and Vibrosonics were the same thing with a different output transformer. Regards, Tim Silverface Changes From [email protected] Mon Jan 12 09:45:50 CST 1998 Article: 79933 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsfeed.internetmci.com!209.150.160.22!newsfeed.wli.net!feed.nntp.acc.ca!204.92.54.104.MISMATCH!news.ican.net!notfor-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: How do Blackface Fenders sound different from Silverface? Date: Mon, 12 Jan 1998 00:10:36 -0500 Organization: ACC TelEnterprises Ltd. Lines: 97 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: ppp-217.m2-5.tor.ican.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: news.ican.net 884578971 8408 (None) 142.154.17.217 X-Complaints-To: [email protected] X-Mailer: Mozilla 2.02 (OS/2; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:79933 Simply Steve wrote: > > Jake122333 wrote: > > > Hi, thanks for reading this. It seems everyone wants a blackface > > instead of a > > silverface fender amp. Can anybody describe the difference in sound > > between a > > blackface and silverface Fender? >> > > Thanks in advance > > Jake > > I think it really depends on what specific amp you're talking about. > Many of the smaller combo amps didn't change much (if at all) in the > early SF days. But I have been under the impression (not having access > to the actual amps, but from reading here for a year or so) that the > later (mid 70s) SFs tend to be brighter, a bit more "clean headroom" and > slightly less "sweetness" possibly due to less distortion (lower B+, > more/different filtering in both amp stages and power supply and even > reverb circuits) - like CBS had some more "audiophile" oriented > engineering and fewer actual rock/blues guitarists working there. I > think they were going for less THD with the SF changes in the bigger > amps and then later in the smaller combos - which is a subjective thing > as far as desirability goes. Many players like the sweet crunch - others excellent description there is no one silverface MOD .. fender continued to "improve" their product over the years as any manufacturer would here is a brief list of things you might find in a silverface amp that wouldn't be in a blackface .. not all amps had all these mods 1) use of jensen speakers was over during the silver era 2) some amps twins supers 68 69 had a weird fixed+cathoed bias output arrangement 3) generally voltages on silverface amps are up at the b+ = more headroom less distortion 4) powersupply :filtercaps were boosted in value choking the compression of the amp: voltage drop resistors were decreased in value running the pre amp at higher voltages, same side effect (no more sweet extended compression) 5) the really good sounding blue interstage caps disappear.. and are replaced by several eras/types of coupling caps some of which sounded awfull 6) the amps go from a really tight well done layout to a sloppier wiring job using plastic wire that flexes and cant be laid out exactly where you want it .. this wire was an "improvement" as some of it was shielded.. the net result was fender started having problems with parasitic oscilation and then killed it and tone by using suppresssion caps here and there 7) almost all fender amps are done as matching bias balance as opposed to the fixed bias method previosly used ... bias is not adjustable but balance is .. resulting in bad tone ... fortunately the parts are the same just hooked up differently.. 8) fender started messing with the cabinets ... dado ing a particle board baffel into the box (different resonance) and when the amp falls (and they do) the baffel is ruined and the replacement job is ugly..the screw in particle baffel board don't crack as easily because of the give of the screw mounting also later silver amp cabinets were doweled together rather than fingerjointed (more of these amps fall ampart) 9) most silver faced amps convert nicely to the older specs .. but as with all things the further you get away from the desirable years the more annoying but important details are changed .. most silver amps never sound exactly like blackface because the power transformers put out a slightly higher B+.. and many techs neglect the powersupply (filters and resistors) in the conversion finally two amps that sound different yet have the same circuit, or seem the same sound different because the powersupply might be different the materials may be very different the speakers and box are a big part of tone 70 to 80% of ammature/ inexperienced techs think that powersupply is not part of the sound of the amp a decent silverfaced amp is stil a far far better value than any circuit board amp currently available re issue or otherwise the key is to find as old a silverface amp as possible and get it set up properly pat Silverface Pro Reverbs From [email protected] Mon Jun 12 10:28:45 CDT 1995 Article: 1704 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!pipex!news.sprintlink.net!uunet!panix!not-for-mail From: [email protected] (Len Moskowitz) Newsgroups: alt.guitar.amps Subject: Re: Blackface vs. Silverface Date: 11 Jun 1995 21:12:50 -0400 Organization: Public Access Internet & UNIX Lines: 24 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> Dr Distortion wrote: >I concur. I own several non-master silverfaces, all from 1971, and >they're good amps that are easily backdated to the blackface circuitry. I >own a '71 Super which I backdated, as well as a real blackface Super. The >silverface sounds as good as the blackface, in my opinion. I recently picked up a '72 silverface Pro-Reverb and checked its circuitry against the blackface schematics. Except for the value of a few caps in the tone circuits, the phase splitter coupling cap value, and the presence of the two 100 Ohm hum balance resistors near the pilot light, and a nice sized electrolytic cap across the bias voltage it was essentially identical, down to the all-RCA 6L6GCs (short with hemispherical heads), 5U4 and pre-amp tubes. The changes that were in there were all real improvements that it doesn't make sense to delete. The thing sounds as good as any blackface I ever played. -Len Moskowitz Core Sound [email protected] Small Trannys Sometimes Better From [email protected] Mon Jan 19 13:30:20 CST 1998 Article: 81080 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!audrey02.news.aol.com!notfor-mail From: [email protected] (MZaite) Newsgroups: alt.guitar.amps Subject: Re: "Presence" on Bassman, What Does It Do? Date: 18 Jan 1998 02:40:48 GMT Lines: 16 Message-ID: <[email protected]> NNTP-Posting-Host: ladder02.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:81080 >What does a larger tranformer do for the sound of an amp? Well as was stated before a correctly matched larger trannie will increase the fidelity of some amps. Will also improve the transparity of sound and the attack will increase. Great for country, jazz,and improved headroom and pick attack, think Mark Knofler. But, bigger isn't always better ( she said ), less iron as in the Pro Reverb and covented Vibroverb ( same trannie BTW, only differant output imp.) can give a natural sounding compression, due to core saturation. The notes seem to swell after the inital attack, also an improved spongy feel, think David Gilmore. http://www.drzamps.com DR.Z Super Champ 6C10 From [email protected] Sat Oct 10 10:25:41 CDT 1998 Article: 131285 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.cwix.com!166.93.8.12!natasha.rmii.com!news.qadas.com!notfor-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Fender Super Champ tubes question Date: Sat, 10 Oct 1998 09:16:49 -0600 Organization: QADAS Online Lines: 11 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: 205-238-99-77.qadas.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.03Gold (Win95; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:131285 > I started thinking about replacing the tubes in my '83 Fender Super Champ > but there's a mystery tube in there. There's the 2 x 6V6's on one side & > the 12AT7 & 12AX7A on the other side, but there's a stubby short tube in > between the sets...does anybody have any idea what this tube is and what it > does? It is a 6C10 tube, which is three triodes in the same bottle, all of which have the same characteristics as the two triodes in a 12AX7. Think of it as a 12AX7 with three triodes instead of two. Steve Super Molestation From [email protected] Wed Jun 28 11:55:39 CDT 1995 Article: 1995 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!usenet.ins.cwru.edu!cleveland.Freenet.Edu!ck983 From: [email protected] (Robert J. Cardinali) Newsgroups: alt.guitar.amps Subject: Super Molested By Tech! Date: 28 Jun 1995 11:14:02 GMT Organization: Case Western Reserve University, Cleveland, OH (USA) Lines: 78 Message-ID: <[email protected]> Reply-To: [email protected] (Robert J. Cardinali) NNTP-Posting-Host: kanga.ins.cwru.edu Ok, so I go to this amp repair place the other day with my mid-60's BF Super Reverb in hand. I have one 6L6 that the center glows red on, and I figure maybe a bias resistor is toast. Easy enough to replace and I think, and while he's in there he can make sure everything's jake. So I pick it up today, and he tells me the tube that was glowing unnaturally was bad, and along with other adjustments, he replaced my shitty "Westinghouse" 6L6's with Sovteks. I think "great, now I get to check out these Rusky tubes that everyone seems to rave about on the net". I run over to my cavernous "secret rehearsal spot" which is really a huge sewing room where I work during the day. The only animal matter that I disturb with volume here are the woodchucks. I kick the switchs on, plug my Strat in and wait with breathless anticipation for some serious aural orgasm....what do I get? Thin, raspy, tinny bottom *from hell*, a distorion that really never quite goes away at any volume level above 2, a nice Les Pauly sustain and definitely a tube amp harmonic mass of sound out of my previously awesome sounding 10 inch alnico love beasties. I can't believe what I am hearing. I am not even remotely amused. I am pissed. What did this retard do to my bell-like-sounding-balls-in-your-face-bottom-end-thatno-other-amp-on-earth-can-produce-except-supers sound? Really, the bass sound is like farting in a tin can, and reminds me of when I was a kid and used to plug into my dads tube VoiceOfTheTheatre tape recorder with the monitor on to get some form of distortion somewhere, anywhere... The Twin-like mids that make you shudder with ecstasy are history. The glassy twang, and prime rib gutsy fullness - gone. Like someone with a bad sense of humor hardwired an SD-1 into the back of this thing and hid it under the reverb can. GodDamn! I think - this dude took my output transformer out, stole all of my filter caps, and replaced it all with Rat Shack parts - Anger wells deep inside of me momentarily. I collect myself, and think of all of the deep dark bad things that are going to happen to this midget when I get my hands on him. I can't find him now, it's after 5 o'clock, and I know I am not going to sleep tonight. Sigh...What to do, what to do....Then I realize....he gave me back my old tubes. I turned the beastie off....let her cool while I pop a brewski and think of how much jail time I am facing for manslaughter...Then when the tubes are cooled sufficiently, I replace them with my cheap MCM "Westinghouse" 6L6's (which looke remarkably like... Yup, the Sovteks)....Kick the switches, and Sho-nuff... My Sound! Hallelujah! I *Don't* have to live in shame anymore! It's back! And it sounds tremendous! Oh happy happy day! I'm A-L-I-V-E! But...what the hell just happened? Am I supposed to believe that people actually think these tubes sound good? Did I maybe, just maybe, get a bad set of Sovteks right out of the box, and did they get past this tech without detection? I can almost believe that some players like that compressed sound and raunch distortion above a nice edgy, CONTROLLED distortion, but there's no curl to ride. It's either there, or it's off...Lame Lame Lame....Yech - Ptoohey! You gotta be shittin me... Now - before I go and make some assumptions I ought not to...Are these tubes rated in the similar fashion that Groove Tubes are? Are there "grunge ratings", in other words? I couldn't imagine going from a balls-out tune like Hideaway or Jukin to a glassy number that Asleep At The Wheel might do, and have that lack of lattitude in my amps...They have to do a wide array of expression, and they absolutely must sound fucking gorgeous when they do it....Please help me understand this. Sovteks are supposed to be the cats whiskers in tubes, no? Did I just get a shitty set? Where oh where can I find a set of NOS RCA's? These Westinghouse tubes look identical internally to the Sovteks too...I wonder... There's no doubt in my mind that these little critters are going back to the shop post-haste. What does a guy have to do? Buy two, three dozen of these suckers and hand pick them for their musical characteristics? There's gotta be a catch here somewhere. Hep me out folx :) Phew..thanks for letting me vent - I might sleep after this bottle of sleeping pills, and that 6-pack of Molson Ale :-) Bob Super Too Much Bass From [email protected] Thu Jun 4 10:06:28 CDT 1998 Article: 108379 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.internetmci.com!199.254.157.46!news.comm.net!notfor-mail From: [email protected] (Ed ) Newsgroups: alt.guitar.amps Subject: Re: Fender Super Reverb Settings? Date: Mon, 01 Jun 1998 03:35:28 GMT Organization: Commnet Data Systems Lines: 26 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: cajun08-port184.cajunnet.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Newsreader: Forte Agent 1.5/32.452 Xref: geraldo.cc.utexas.edu alt.guitar.amps:108379 On Thu, 28 May 1998 02:30:17 -0700, Alan Thompson wrote: >I'm just curious about one thing here, and that is the bass set at 10. In my >experience, Fender amps have too much bass, and anything over about 4 results in a >lot of "woofiness" in the bass. Is your amp stock, and have you tried setting the >bass lower? When I first got my blackface Super Reverb, the amp was "woofy" or "farty", and I couldn't turn the bass up too high. The first thing you should do is make sure all the electrolytics are in good condition. Get a good cap job, if you can afford it. Your amp will thank you. Next thing, check out the capacitor coming from the normal and vibrato channels into the phase inverter (driver) section. I think there's two 220k resistors going into this cap. If it's too large, it will be excessively bassy. I think that cap should be .001, but people modify it like that Weber's book to a .01, which will give you way too much bass response, and it will quickly get muddy at higher volume levels. Also, if you pull out the wire between your treble and volume and insert a .001uF to .0022 capacitor, it will cut out all of the sub-bass garbage that goes through all your gain stages and muddies up the amp. Your amp will be tighter, and you can turn up your bass quite a bit higher at good volume levels, and your amp will have a nice warm tone and a solid "kick" as opposed to the woofy fart syndrome. Tolex Repairs From [email protected] Wed Jul 1 15:55:24 CDT 1998 Article: 113253 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!news.maxwell.syr.edu!nntp2.dejanews.com!nnrp1.dejanews.com!notfor-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Tolex Repair (Help) Date: Wed, 01 Jul 1998 20:43:40 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 40 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: 208.197.111.2 X-Article-Creation-Date: Wed Jul 01 20:43:40 1998 GMT X-Http-User-Agent: Mozilla/3.01 (WinNT; I) Xref: geraldo.cc.utexas.edu alt.guitar.amps:113253 In article <[email protected]>, [email protected] wrote: > >> > > Not sure how many holes and scuffs you've got but sounds like you might consider recovering > > it? I haven't tried this myself but I recall a couple of places selling tolex (Mojo > > I'm pretty sure is one) or you could send it in and have them redo it (I'm sure that's > > expensive). > Only two holes, and a few scuffs...I really don't want to Spend the > money to recover this fully (OK, I'm one of those folks who thinks > a little age showing in guitars and amps is necessary). I've never tried > the Tolex repair stuff advertised in VG magazine, I wonder if anyone > else has successfully used it. > Randy > I just finished a repair for a friend that sounds alot like this. The amp was a 67' deluxe reverb that some misguided soul had installed a set of tilt back legs on. Actually I kinda liked being able to do the tilt-back thing but this being the age of vintage PC BS the legs had to go. Using 1/8" dowel stock, I cut 4 short pieces and glued one into each of the holes in the cabinet. Make sure you recess the dowels a bit to allow for the thickness of the tolex on the outside of the cab. On the inside of the cab I used one of those nifty flexible flush cut saws ($7.00 at Home Depot) to cut the dowel flush on the inside of the cab. With all of the holes filled in I could now fix the tolex. Using a hole punch (like for putting papers in a three ring binder) I punched a few round "plugs" out of some gen-u-ine BF era tolex that I have lying around from a 66' SR that I'm recovering. If you don't have any tolex handy just snip a few inches off from some of the excess glued to the inside of your cab. My local office supply superstore had a nice assortment of diameters for the punches and I found one that was ~1/8". I imagine a leather punch or even a piece of small diameter copper pipe could be used to make the plugs. Last step was to glue the plug into place over the dowel using a little white glue. Hope this helps. -----== Posted via Deja News, The Leader in Internet Discussion ==----http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum Tremolo Tick Tips From [email protected] Mon May 26 11:33:32 CDT 1997 Article: 50907 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.nacamar.de!newskar1.dfn.de!news-stu1.dfn.de!news-mue1.dfn.de!news-nue1.dfn.de!uni-erlangen.de!lrz-muenchen.de!not-formail From: [email protected] (Simply Steve) Newsgroups: alt.guitar.amps Subject: Re: ticking Vibrato? Date: Mon, 26 May 1997 01:41:58 GMT Organization: [posted via] Leibniz-Rechenzentrum, Muenchen (Germany) Lines: 19 Distribution: world Message-ID: <[email protected]> References: NNTP-Posting-Host: baracka.rz.uni-augsburg.de X-Newsreader: Forte Free Agent 1.1/32.230 Xref: geraldo.cc.utexas.edu alt.guitar.amps:50907 On Fri, 23 May 1997 12:29:49 -0700, [email protected] (Scott Davey) wrote: >Yes, the Vibrato in my Silverface Twin ticks when on, no input necessary. >Is there a simple fix for this? Thanks! Cleaning up the lead dress around the vibe circuit, touching up shitty solder joints in that area. and melting off excess circuit board wax (possibly trapping moisture?) with a hairdryer all but eliminated the tick in my SF Virbolux Reverb. Be carefull not to overheat components with the hairdryer, though, just get it warm enough to allow the excess wax to drip off (with the chassis at about 45 degree slant). Mine had enough wax to make several emergency candles! Simply Steve "If God had intended for us to play guitars, He would've given us 6 fingers." (on one hand, that is) [email protected] Tweed Champ Filter Caps From [email protected] Tue Mar 10 23:07:15 CST 1998 Article: 90070 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!uwm.edu!newsfeeds.sol.net!wnfeed!204.127.130.5!worldnet.att.net!newsadm From: "Michael" Newsgroups: alt.guitar.amps Subject: Re: Champ/Filter cap question Date: Tue, 10 Mar 1998 08:42:59 -0800 Organization: AT&T WorldNet Services Lines: 39 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: 12.65.70.56 X-Newsreader: Microsoft Outlook Express 4.71.1712.3 X-MimeOLE: Produced By Microsoft MimeOLE V4.71.1712.3 Xref: geraldo.cc.utexas.edu alt.guitar.amps:90070 Henry, I spent some time learning what effect cap values have on an amps sound when I built my first amp. I used the 5E1 and 5F1 Champ circuit, homebuilt . The stock 5E1 used a choke between the first two caps and the 5F1 uses 10K 1watt resistor. Basically I found that the Champs with only 3X8uf caps could not afford to have fewer caps because of the need to decouple different sections of the circuit. Trying to take the B+for the power tube and preamp tube from the same location would be a disaster. 3 caps are required for this circuit IMO. In terms of capacity going to 3X4uf made the sound even spongier but the noise and hum went up. Changing to 3x16uf got rid of the hum dramatically and the sound tightened up just a little. I then tried 16uf, 47uf, 47uf goin down the line and the single ended hum nearly vanished. The amp lost a little bit of its lively flavor though. Even though it is hard on the 5Y3 rectifier tube I tried 100uf, 100uf,100uf. Hum now all but gone and so was a lot of the springy, spongy Champ character. My favorite combination was in the 5E1 layout using a 5h choke with 3X16uf caps. this combined with using a false center tap heater arrangement for the low hum gave me the tone and the low hum I was lookin for. Basically I found more capacitance lowered hum but compromised the sound . 3X16uf seemed like the best compromise. Using a choke instead of a resistor seemed to give the amp a little more headroom before breakin up. I also tried using oil caps instead of electrolytics. Love that oil cap sound in power supplies, but there is no room for them on a factory built amp chassis. My feeling after fooling around with this for several days was that the low capacitance of the orignal tweed champs was an integral part of their sound. Change the caps dramatically, and the sound does also, and not for the better IMO. Michael remove x's to respond direct Henry Mabry wrote in message <[email protected]>... >What would adding or removing filter capacitors do to a Tweed Champ? >i.e. How does it affect clean vs. crunch? How does a choke's >function compare with the capacitor's? >Thanks. > Tweed Deluxe Bypass Cap From [email protected] Wed Sep 16 18:11:46 CDT 1998 Article: 127237 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!newspeer.gip.net!news.gsl.net!gip.net!portc01.blue.aol.com!audrey03.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Biasing a Tweed Deluxe? Lines: 14 NNTP-Posting-Host: ladder03.news.aol.com X-Admin: [email protected] Date: 16 Sep 1998 21:51:39 GMT Organization: AOL http://www.aol.com References: <[email protected]> Message-ID: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:127237 >I used a 250 ohm with a 5 watt rating. Should be fine. A 10 Watter would provide additional safety margin and cooler operation. >The schematic calls for a 25 microfarad at 25 volts. True enough. However, if you actually measure the voltage across the cap it will usually be right at 25 volts or maybe a little higher. Bad idea. Use a cap with a higher voltage rating for safety sake. The 25 uF number results in spongier sound as you drive the piss out of it. 47 UuF tightens it up a bit. Tweed Deluxe Transformers From [email protected] Tue Jan 7 13:41:09 CST 1997 Article: 33516 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohiostate.edu!howland.erols.net!newsfeed.internetmci.com!news.campus.mci.net!n-f-m From: "murali@kalimusic" Newsgroups: alt.guitar.amps Subject: Re: schematic for deluxe brownface Date: Tue, 07 Jan 1997 09:26:13 +0000 Organization: Kali Music on the Internet Lines: 34 Message-ID: <[email protected]> References: Reply-To: [email protected] NNTP-Posting-Host: s06-pm06.snaustel.campus.mci.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0Gold (Macintosh; U; 68K) Robert Fries wrote: > > [email protected] (Ted Matsumura) wrote: > > >Can anyone tell me which of the tube amp books contain a schematic for > >the '62 deluxe brownface which uses 2 6L6, GZ34, 7025s (12AX7) I > >understand this is a fixed bias amp, unlike the tweed era deluxes. Also, > >is this an A/B design or pure class A? Does this unit use the same > >transformers as tweed or blackface reverbs? > > It's in the Tube Amp Book (Model 6G3). class A/B, same output transformer as > the Blackface and Silverface Deluxe and DeluxeReverb. The power transformer > is different from the later amps, and the schematics don't show the part > numbers for the transfomers on the tweed Deluxe. > > RF > > ***************** > Robert Fries > 415-988-9475 > [email protected] > ***************** Tweed Power Trans: Triad 6452; Output Trans most likely: 1839. this info came to me courtesy of Doug Hoffman. He's worked on a few of these and says this is what they all had. My '50 DeLuxe has the 6452 Triad, but the OT is not original. I think it's # 022913. BTW, Mojo sells a nice set of Fender schemos in velo bound books. Three series: Tweed, White/Brown, and Blackface. Contact me or any Mojo dealer for a price. m. m. Tweed Twins From [email protected] Sat Oct 10 19:57:40 CDT 1998 Article: 131286 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!howland.erols.net!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!portc02.blue.aol.com!audrey03.news.aol.com!not-for-mail From: [email protected] (Timeque) Newsgroups: alt.guitar.amps Subject: Re: Low Power Tweed Twin? Lines: 25 NNTP-Posting-Host: ladder02.news.aol.com X-Admin: [email protected] Date: 10 Oct 1998 15:31:58 GMT Organization: AOL http://www.aol.com References: <[email protected]> Message-ID: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:131286 A low powered tweed Fender Twin -- the amps built from 1953 to about 1958 -- do not sound like Fender tweed bassman. Two twelve inch speakers do not sound like four tens. However they sound damned good, and there is a definite tweed family genetic marker. The tweed twins went through various circuit and tube changes from their inception. The first had seven pin, metal can preamp tubes, and two 6l6s with a single rectifier tube. Like a tweed deluxe they are cathode bisased. They only put out about thirty watts, but they have more tonal impact and "spread" because of the baffle width and twin twelves. They start to compress past three on the volume knob...but the compression is delicious. And for playing blues, you can hear why these things are in such demand. With single coils at about 12 oclock on the volume dial, the amps are so touch sensitive they're like electric blues heart/lung machines! Later changes in the mid nine-teen fifties were 12ax7 and 12 ay7 preamp tubes...circuit modifications...the dual rectifiers...changes to the biasing schemes...all in an effort to make the lamps play louder. You can trace the circuit changes by looking at Pittman's or Webers amplifier books. Any of the twee twin amps...if you can find them...are capable of sounding great. Haven't heard the reproductions, so I can't comment. Anyway, the great lesson with Leo's tweed machines is that while volume is good...TONE IS GOD...and in my opinion Leo had his godliest moments in the nineteen fifties. From [email protected] Sat Oct 10 20:00:00 CDT 1998 Article: 131304 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!newsnyc.telia.net!newsfeed.cwix.com!152.163.199.19!portc03.blue.aol.com!audrey03.news.aol.com!not-for-mail From: [email protected] (Timeque) Newsgroups: alt.guitar.amps Subject: Re: Low Power Tweed Twin? Lines: 32 NNTP-Posting-Host: ladder02.news.aol.com X-Admin: [email protected] Date: 10 Oct 1998 17:46:38 GMT Organization: AOL http://www.aol.com References: <[email protected]> Message-ID: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:131304 Alnico 2 is misinformed. Tweed twins were built from late 53 on. There was an article in Vintage Guitar Magazine (the glossy) by Gerald Weber a few years ago. It's got wrong information in it (thanks Gerald, again), but it has a photo display of Tweed Twin Serial number 223. It's owned by a dealer in New Hampshire, and it is the proverbial amp that lived its life in a closet. The 1955 series Tweed Twins are the one where Leo made his first revisions to the circuit to gain more volume. Note the difference between 5c8 and 5d8 schematics...also note that early 5d8s had a single rectifier tube...later one had the two rectifiers tubes to make them go louder...like the one Clapton plays as his personal amp. I helped restore tweed twin serial #224, (yes, the one right behind the amp that ended up in the closet in New Hampshire.) This amp was bought brand new by a pedal steel player in 1954. He tore the jensens out and put in Altecs in the sixties, and he got rid of the tweed and put on naugahyde and pillow padding. We restored the original speakers and Paul Lamb retweeded it. Before we did anything to the amp, we found out as much as we could about early tweeds. Best, timeque PS: the famous photo of BB KING playing in bermuda shorts at a Missippi concert shows him playing a tweed twin...not as commonly assumed, a Super. Check the album DO THE BOOGIE -- EARLY FIFTIES CLASSICS (rhino release) if you want to hear the sound through a hollow body and p-90 pickups. Twin Reverb History From [email protected] Fri Jan 12 12:35:19 CST 1996 Article: 7844 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!usc!howland.reston.ans.net!nntp.coast.net!news.net99.net!newshost.cyberramp.net!news From: [email protected] (David Taylor) Newsgroups: alt.guitar.amps Subject: Re: FENDER TWIN REVERB MODIFI Date: 12 Jan 1996 03:48:16 GMT Organization: CyberRamp Lines: 57 Distribution: world Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: tsa1-10.cyberramp.net Mime-Version: 1.0 Content-Type: Text/Plain; charset=ISO-8859-1 In article <[email protected]>, [email protected] says... > >Subject: Fender Twin Reverb Modifications > >I seem to notice that various Fender Twin Reverb amplifiers have various >colors & names in their title on the front panel. Some I've seen include: > >* Black front with white "Fender Twin" on it > >* Silver front with blue "Fender Twin" on it > >* Silver front with green "Fender Twin-Reverb Amp" on it > >* Silver front with green "The Twin" on it Not familiar with many of these variations. The history of The Twin and Twin Reverb is such: Twin Amp First Tweed Version: 1952. 15 watts. Twin Amp Second Tweed Version: 1954 50 watts. Twin Amp First Tolex Version (Brown Tolex): 1960 90 watts. Blackface, "pre-CBS" Twin Reverb: 1963 85 watts. Silverface Twin Reverb (silver face plate with blue letters) 1968. 85 watts (very similar circuit to blackface, inappropriate major circuit changes made initially, but most reversed almost back to pre-CBS specifications within months. All examples of this version can be easily and inexpensively modified to exact blackface specifications by a competent tech) Second Silverface Twin Reverb Version: 1973 100 watts and a perfectly cheesy sounding master volume control. Third Silverface Twin Reverb Version: 1976 100 watts and a push/pull distortion switch on the master volume control pot. Second Blackface Twin Reverb Version: 1981 135 watts (ouch) After 1982 no more Twins or Twin Reverbs shipped until 1987. The Twin: 1987 100 watts. First post-CBS Fender amp. Black control panel with red knobs. Later black knobs. Recently redesigned. Twin Reverb Vintage Reissue: 1992 85 watts. A recreation of the pre-CBS blackface Fender Twin Reverb. Severely Opinionated Editorial Comment (SOEC): Doesn't sound too much like the original, but with a new old stock or reissue paper-wound output transformer (new on the market and way overdue!) and a pair of Mojo, Naylor Special Design 50 or Hudson speakers (close sounding knockoffs of the original blackface Jensens), this amp really comes alive. Twin Reverb Variants From [email protected] Tue Aug 29 21:56:11 CDT 1995 Article: 3225 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.sprintlink.net!ns1.usa1.com!danmad125.usa1.com!user From: [email protected] (Rod Daynes) Newsgroups: alt.guitar.amps Subject: Re: FENDER TWIN INFO? Date: Wed, 23 Aug 1995 12:14:31 -0400 Organization: Clamnet Lines: 62 Message-ID: References: NNTP-Posting-Host: danmad119.usa1.com In article , [email protected] (dudahman) wrote: > can someone please give me the lowdown on an old twin vs. a new twin, and > what should the cost be? Thanks! Fender Twin amps have been likened to ³apple pie² in the book, Fender Amps: the First Fifty Years (Teagle & Sprung, Hal Leonard Publishing, 1995). Here¹s what they say: ³An old Twin is like Grandma¹s pie, hot out of the oven, simple and delicious. The Silverface Twin Reverb, a dependable workhorse for years, is like a piece of diner pie ... and a 1995 ŒTwin-Amp,¹ with its 40-plus years of advanced technology, is for the more adventurous -- nouvelle cuisine, so to speak.² You can look at the Twin series in three distinct groups: Group 1: Early Twins and ³Blackface² Twins The 1950¹s Twins (tweed) are truly vintage, and according to the latest issue of Vintage Guitar Magazine, can go for as much as $3,000. The Blackface Twins (Twin Reverb), circa 1963-68, are slightly more affordable vintage amps, and very desirable, in terms of raw power and clean sound. Here¹s an amp with roughly 85 watts RMS, 4 6L6 tubes, 2x12² speakers, reverb, and two independent channels. Really nice, if you can find one in good condition. Blackface Twins, particularly the 1965 year models, are considered by many to be THE standard of all combo amps. Price ranges for Blackface Twins are $800-1,100. Group 2: ³Silverface² Twins Although less desirable to collectors than their blackface predecessors, due in part to Fender¹s unfortunate association with CBS from 1964-1984 (CBS also tarnished the reputations of Steinway Pianos, Rogers Organs, and Gemeinhardt Flutes during this period), the Silverface tube-based (I repeat: tube-based) Twins are none-the-less great sounding and powerful amps, similar in most respects to the Blackface Twins, and they can be purchased at bargain rates for around $500, sometimes less. Group 3: ³Red-Knob² Series and ³Twin-Amp² The red-knob Twins are among the first produced by the new (old) Fender, after CBS sold it back to execs who really cared about great craftsmanship, innovation, and great sound. The red-knob series hit the streets beginning in 1988, and continued until the release of the "Twin-Amp," in 1995. For my money, the red-knob Twins (characterized initially by red knobs, dark grill-cloth, and face-plates bearing the name ³The Twin²), are the best of the lot, owing to their unbelievable power, richness, and versatility. Some of these features include: 100 or 25 watt switchable output, effects loop, switchable channels, power and pre-amp jacks, line out jack, a wicked tube-based distortion, push-pull EQ and presence boost pots, and reverb. Price range: $650-800. The new 1995 Twin-Amp is similar to the red-knob Twins, just a bit more retro in terms of looks. Retail for the Twin-Amp is about $1000. To be sure, there are other Twins, including the Super Twin and Super Twin Reverb, and Fender¹s ³re-issue² Twin Reverb, which is based on the Œ65 Blackface, but these are branches off the main trunk. Open a re-issue Twin and you'll see printed cicuit boards, for example. These amps are not bad alternatives, but not as desirable as the original, in my view. I didn¹t mean to turn this reply into an essay, but you asked a big question, and the Twin series deserves every bit the admiration it gets >from pros and amateurs alike. Cheers, Rod Twin Reverb overdrive From [email protected] Sat Aug 24 16:04:25 CDT 1996 Article: 21438 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!nntp04.primenet.com!nntp.primenet.com!mr.net!news.sgi.com!news.msfc.nasa.gov!newsfeed.internetmci.com!in3.uu.net!ulowell.uml.edu!news.onramp.net!usenet From: [email protected] (David Taylor) Newsgroups: alt.guitar.amps Subject: Re: Fender Twin Reverb Amp Date: 24 Aug 1996 05:44:18 GMT Organization: Onramp Lines: 55 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: stemmons21.onramp.net Mime-Version: 1.0 Content-Type: Text/Plain; charset=ISO-8859-1 X-Newsreader: WinVN 0.99.5 In article <[email protected]>, [email protected] says... > >[email protected] (TimTube) wrote: > >>Simply taking out the tone stack is effective for a modest gain boost, but >>this will not put you over the edge, which sounds like this guy wants to >>go. Simply disconnecting the midrange pot from ground removes the tone >>stack. I have done this using the existing bright switch on many Fenders. >> >>If you are not intimately familiar with the inside of tube amps, have a >>tech do this. YOU CAN DIE. >> >>Shouldn't cost more than $20 or so. > >Tim >thanks for you reply. I'm not a tech, so i don't know exactly what Roy does. He DID NOT say that the only thing he does is take ou= >t the tone stack. Paul Patronete of Groove Tubes has HEARD the result of this mod, and he says it sounds like a Marshall. Don't y= >ou think he would know what a Marshall sounds like? >I still think it's worth a call to Roy or Paul if you're interested in a mod like this. If I may add my two cents: One overlooked, and very simple solution on pushing that reissue 65 Twin over the edge would be to do what I've been doing for years. Use pedals. There's no shame in it. Hendrix did it. Eric Johnson does it. Stevie Ray did it. What I've done with GREAT success with a Twin Reverb is to use TWO tube screamers (TS9's with at least one authentic with the JRC4558 OpAmp chip). Here's how: You place the original one first in the chain, settings on Drive=2:00, Tone=12:00 and Level=2:00. Then place the reissue TS9 second in the chain with all settings at 12:00. Turn the Twin Reverb up to 4. When you kick in the tube screamers it drives the gain up enough to fill any room without the speakers flapping out, and when you disengage you get a great clean sound. Also, when you use just the lower set Tube Screamer, you get a good crunch-tone; When you use only the higher-set (vintage) Tube Screamer, you get great blues; And when you use them both you get FIRE. The other thing that works exceptionally well in conjunction with these pedals is a set of Celestion or Mojo Vintage 30's. It's like they were made for that amp. Hope this gets you to at least consider a less evasive alternative. Vibrato Click Fixes From [email protected] Thu Dec 11 22:58:39 CST 1997 Article: 75500 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!newspeer.sprintlink.net!news.sprintlink.net!Sprint!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!newstf02.news.aol.com!audrey01.news.aol.com!notfor-mail From: [email protected] (TROOBKA) Newsgroups: alt.guitar.amps Subject: Re: Super Reverb Vibrato help Date: 12 Dec 1997 04:32:59 GMT Lines: 7 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:75500 Being a 69' I would say it is the lead dress on the Vibrato circuit. The usual way to fix it is to pull the wires that connect to the vibrato speed and intensity controls away from the tone controls, bunch up the leads which to to the components on the eyelet board. Then place a .022mfd\630 volt cap across the 10 meg resistor in the vibrato circuit. Hope this helps, Mark Vibrato Tick Svc Bltn 9 From mutantmoose*nospam*@worldnet.att.net Mon Jan 26 18:49:12 CST 1998 Article: 82232 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!worldnet.att.net!newsadm From: "Mutantmoose" Newsgroups: alt.guitar.amps Subject: Re: Deluxe Reverb vibrato noise help! Date: 25 Jan 1998 16:42:38 GMT Organization: Preferred Company Lines: 52 Message-ID: <[email protected]> References: <01bd2917$fce080c0$5b775acf@mike> NNTP-Posting-Host: 12.64.5.207 X-Newsreader: Microsoft Internet News 4.70.1157 Xref: geraldo.cc.utexas.edu alt.guitar.amps:82232 The official Fender solution (Service Bulletin number 9) "The ticking cuased by the Vibrato is caused by improper lead dress. It can almost be "cured" by connecting a .01 mfd 600 volt mylar capacitor on the 10 meg ohm resistor in the vibrato circuit. this resistor is located on the parts panel. Remove capacitor across the 10 meg ohm resistor (old modification) if in place." (That is, run the cap from the junction of the 10 meg resistor and the optoisolator to ground.) "If this does not produce the desired results, then the leads shoul dbe dressed as follows and excessive lengths shortened. 1. Dress the leads to the vibrato speed and intensity controls away from the tone controls and filter leads. 2. "Bunch" the leads to the components on the parts panel which connect to the tube socket of the 7025 (12AX7) vibrato tube." Hope this helps! Mark [email protected] you know the routine, remove -nospam to reply Mike wrote in article <01bd2917$fce080c0$5b775acf@mike>... > I just picked up an older (blackface) Fender Deluxe Reverb. There is a > slight "ticking" noise associated with the vibrato circuit. The "ticking" > changes with the speed pot. I figure it might be a 12AX7A tube that's going > bad, or a bad capacitor. This amp has one of each - volume, treble, bass, > reverb, speed, and intensity knob, on the vibrato channel. The normal > channel has 3 knobs, volume, treble, and bass. I picked up this amp at the > Columbus, Ohio Winter Guitar Expo last week. It's in "WELL USED" shape, but > it has the tone! I'll need to pick up as book of schematics for Fender amps > (I also have a silverface VibroChamp and a SS Harvard Reverb II), can > anyone offer a suggestion on which publication to get? > In case your interested, I paid $400 with foot switches and cover. > > Thanks, > Mike > (NO_SPAM)[email protected] > > > > Vibro King fat switch From [email protected] Tue Nov 22 13:16:36 CST 1994 Article: 28664 of alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.reston.ans.net!news.sprintlink.net!deathstar.cris.com!voyager.cris.com!notfor-mail From: [email protected] (Dr.Distortion) Newsgroups: rec.music.makers.guitar,alt.guitar Subject: Re: Vibro King == no feedback loop? Followup-To: rec.music.makers.guitar,alt.guitar Date: 17 Nov 1994 19:27:26 -0500 Organization: Concentric Research Corporation Lines: 32 Distribution: world Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: voyager.cris.com X-Newsreader: TIN [version 1.2 PL1] Xref: geraldo.cc.utexas.edu rec.music.makers.guitar:32903 alt.guitar:28664 David Covell - MPG DA ([email protected]) wrote: : I persuaded the salesman to let me look at the schematic and was suprised to : see no sign of negative feedback. Either I'm blind or Fender's using the lack : of feedback to increase warmth and open up the low end. You're right. I have the schematic, and there's no -FB loop. : Unfortunately I didn't have time to locate the fat switch implementation; with : the huge transformers and the lack of feedback it wouldn't surprise me if the : fat switch, when engaged, is actually the amp's normal voice, and that turning : the switch off just switches in a cap to roll off some bass. Good guess, but that's not it. The fat switch puts a 22uF bypass cap across the first stage cathode resistor, which increases the gain at low frequencies. It's an old trick that's been used in other amps, usually labeled as a "bass shift" or some such (a la Boogie). : At any rate, I really liked the amp; I wouldn't say it sounds any better than : a good vintage Fender but it certainly has more depth to the low end. Now if I : could just get my Showman to sound that way I'd be content (for a while, at You can get a lot more bass out of your Showman by replacing the coupling cap to the phase inverter (typically .001uF) with a .01uF cap. ________________________________________________ _|__|_ / ==|== \ / ==|== \ | --------|--\/\/\/\/\/\/\/\/\/\/--|-------- | -|-------- | /\/\/DOCTOR/\/\/\/ | --------|\_|~~~|_/ /\/\/DISTORTION\/\/\/ \_|~~~|_/ ~~~| /\/\/\/\/\/\/\/\/\/\/ |~~~ -----*STAUDCO*---*New York*--*[email protected]*--- Vibro King info From [email protected] Tue Oct 18 11:03:11 CDT 1994 Article: 26391 of alt.guitar Newsgroups: alt.guitar Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!pipex!uunet!tandem!NewsWatcher!user From: [email protected] (Jim Collins) Subject: Re: Vibro-King Amps Message-ID: Followup-To: alt.guitar Sender: [email protected] Nntp-Posting-Host: 130.252.1.130 Organization: Tandem Computers, Inc. References: Date: Mon, 17 Oct 1994 23:51:03 GMT Lines: 51 X-Disclaimer: This article is not the opinion of Tandem Computers, Inc. In article , [email protected] (Pavelec, Rish) wrote: > > Has anyone out there tried Fender's Vibro-King Amp? I think it's 100 Watts > with 4 12's and was wondering if you have to turn it up to 8 before you get > any tone (not sound) out of it. > > The ususal arguement is: 45-60 watts with 4 10's have good tone a low > volumes but not enough bottom end. 100 Watts of 4 12's have good bottom end > but you need to blow the windows out before you get any tone. > > Comments? I have a Vibro King. I is not 100 watts, nor does it have 4 12-inch speakers. It is 60 watts, and it has 3 10-inch speakers. It has an incredible reverb section, with the same reverb controls as are found on the Fender reissue reverb -- dwell, mix, and tone. It has a good tremolo section, if you are into that sort of thing, though the speed control does not have the range of an old blackface amp's tremolo. By that I mean the Vibro King's speed control is not as smooth -- there is very little variation of speed in the first one-third to one-half turn of the knob, then there is a lot of variation. This is a single channel amp, with no drive or lead mode. It does have a fat switch which is now footswitchable. (According to an early review I read, the fat control was not footswitchable. It is on mine.) The fat switch is a nice touch. I generally use it with single coil pickups, and turn it off with humbuckers. This is a loud, clean amp. It is not as loud as an old Twin Reverb (85 watts), nor is it as bright as a Twin. It is clean. It is a very nice clean, though. The 10-inch speakers really punch out the sound, and it seems to respond very well to varied pick attack. Dig into the strings, and you'll hear it. I think it has plenty of bottom end, though I wouldn't play bass with it. You don't have to push this amp up far for it to sound good. I usually set it below 4 for gigs. (The band would neuter me if I turned up past that.) I also turn the bass, treble and mid controls all the way up. The guitar I use most often is a '52 reissue Tele, though I also use Strats and Les Pauls. (A Les Paul with P-90s is really nice through this thing.) The Tele gives a great, full sound. You might think that an amp set at below 4 won't give you much in the line of full-bodied sound. This is not the case. A '62 reissue Strat, with Seymour Duncan Alnico II Pro pickups roars with the volume on 3 1/2, tone controls pegged, fat switch on, and generous reverb. A Les Paul with humbuckers on this setting will overdrive very easily. I really like this amp, but I'll tell you the truth. I wish it were a 40 or 45 watt amp. Most of the places we play couldn't take this bad boy at 7 or 8. It would be easier to grab that Roy Buchanon screaming Tele bridge pickup sound in a lower powered amp. But still, this has all the sounds I want, even at a low volume. (I've never even tried putting a distortion box between my guitar and this amp. The clean sounds are too nice.) Jimmy Vibroverb tone From [email protected] Wed Jun 7 13:13:02 CDT 1995 Article: 1631 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!swrinde!howland.reston.ans.net!newse1a.megaweb.com!newstf01.news.aol.com!newsbf02.news.aol.com!not-for-mail From: [email protected] (Tremolux) Newsgroups: alt.guitar.amps Subject: Re: Fender Vibrolux-Rever Date: 7 Jun 1995 12:02:01 -0400 Organization: America Online, Inc. (1-800-827-6364) Lines: 28 Sender: [email protected] Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] (Tremolux) NNTP-Posting-Host: newsbf02.mail.aol.com The only Brown Vibroverb I've ever heard is one of the new reissues. Those sound a bit thin and are not so loud. I've never seen an AA763 anything. Re the AB763 Vibroverb, they sound great. They're much louder and fatter sounding than the brown 6G16. The amps that use modulated bias to achieve tremolo sound best IMO, for that particular function. The LDR method as used on most of the later tolex amps works, and if you've heard one, they all sound similar on the tremolo. Comparing a Vibroverb to a Twin, the Verb has a little more bass since it has the 15. The Twin is louder since it has 3 dB more power. If you look at the schematics, you'll see that the preamps are almost identical, so the tone is very similar. Re the Reverb, again, I've not had much experience with the brown amp, so let me just say that the BEST reverb I've ever heard comes from an old Ampeg Reverberocket or Super Echo Twin or the Fender tube reverb unit. The reverb pans used over the years by Fender are virtually identical. 2 springs, low input impedance, high output impedance. They all sound pretty much the same unless there's something wrong. How do you describe sound in writing? What sounds like shit to one man may be another's ultimate tone. Fenders have a unique tone signature, they're pretty similar. Then there are the old Tweeds....... Regards. What Makes Fender Sound From [email protected] Thu Jul 16 19:31:22 CDT 1998 Article: 116002 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!feed2.news.erols.com!erols!not-for-mail From: Mark or Cyndi Van Ditta Newsgroups: alt.guitar.amps Subject: Re: Fender Sound Date: Thu, 16 Jul 1998 16:13:28 -0400 Organization: RCN Internet Lines: 34 Message-ID: <[email protected]> References: <[email protected]> NNTP-Posting-Host: 207-172-150-17.s17.as8.anp.erols.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: winter.news.erols.com 900619846 4228 207.172.150.17 (16 Jul 1998 20:10:46 GMT) X-Complaints-To: [email protected] X-Mailer: Mozilla 4.01 [en] (Win95; I) To: Mickey Ilardi X-Priority: 3 (Normal) Xref: geraldo.cc.utexas.edu alt.guitar.amps:116002 Mickey Ilardi wrote: > What gives Fender amps their unique (clean) tone? Is it in the pre > amp > stage or the power amp stage? I have tried and owned numerous all > tube I believe a lot of the sound can be attributed to the placement of the EQ, its slope resistor, and the .001 coupling cap between the preamp and the modified-Schmitt-splitter. Placing the EQ between the first and second stages of the preamp definitely does a good job of cutting down on gain. The 100K slope resistor most definitely gives the stack a much bigger dip in the middle frequency range (as well as shifts the center point down in frequency), and the .001 coupling cap thins down the signal reaching the power stage. All in all, I think what makes Fender sound like a Fender is the emphasis on upper frequency content while subduing middle and lower content. The loss of low-content in the preamp and phase inverter stages is made up from the big-bottom produced by most 6L6-type tubes. To my ear, in a Tweed-type circuit, 6L6-type tubes tend to be boomy and muddy at high volumes. The classic, tweed-era circuit that is used in a most Marshalls is optimized for gain (i.e., the use of the cathode follower to isolate the tone stack from the previous gain stage). The EQ has a more shallow slope; thus, the EQ has much less control over the middle frequency range. The .02 coupling cap between the tone stack and the modified-Schmitt-splitter allows more mids and lows to reach the power stage; thus, producing a thicker sound. Mark What Was Ice Cube From [email protected] Sun Apr 5 11:04:45 CDT 1998 Article: 96003 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!audrey02.news.aol.com!notfor-mail From: [email protected] (TimTube) Newsgroups: alt.guitar.amps Subject: Re: The Cube Date: 5 Apr 1998 14:41:01 GMT Lines: 20 Message-ID: <[email protected]> NNTP-Posting-Host: ladder01.news.aol.com X-Admin: [email protected] References: <[email protected]> Organization: AOL http://www.aol.com X-Newsreader: AOL Offline Reader Xref: geraldo.cc.utexas.edu alt.guitar.amps:96003 In article <[email protected]>, Alan Thompson writes: > >Are you referring to the "Ice Cube"? - I know a little about those. If not, >just ignore my response! > > The original Ice Cube was a little ice cube shaped device that plugged into the reverb input and output on Fender amps. It merely connected the input and output jacks, there may have been a resistor in there. This converted the reverb circuit into a cheesy harsh sounding overdrive. You can get the same effect with a wire w/ 2 RCA jacks. There was a later version that allowed you to switch between reverb and overdrive, and may have had some controls. Tim A great amp can make a lousy guitar sound great. A lousy amp will make a great guitar sound lousy. What is Hi Pot From [email protected] Sat May 2 23:37:10 CDT 1998 Article: 102312 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!Supernews73!supernews.com!Supernews69!not-formail From: [email protected] (Ned Carlson) Newsgroups: alt.guitar.amps,rec.music.makers.guitar Subject: Re: Fender "PASS HI-POT" Sticker ?? Date: Sun, 03 May 1998 04:24:39 GMT Organization: Triode Electronics Lines: 28 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] X-Trace: 894169310 IG5G0KQDTA0D3C7B3 usenet36.supernews.com X-Complaints-To: [email protected] X-Newsreader: Forte Free Agent 1.11/16.235 Xref: geraldo.cc.utexas.edu alt.guitar.amps:102312 rec.music.makers.guitar:201933 On Sat, 02 May 1998 19:38:45 -0600, [email protected] wrote: >Both my Blues Jr. and my Prosonic have a small white sticker on the speaker >baffle board which says: PASS HI-POT. Anyone know what this means ? That's what happens after you eat funny brownies.. But seriously, folks, Hi-pot is a high voltage test applied to a transformer to make sure the things won't fail in normal use, and will take normal amounts of abuse (typical line surges, etc). For example, a 120VAC primary power xfmr might be hipot tested to 1500 or 2000 volts. IIRC, this is required to get a UL listing or a CSA sticker. >I've already discarded the possibilities that the inspector was either a drug >user or Cambodian. ;) Who knows how many people Leo Fender had whacked on his path to becoming a Tube Amp Immortal....just kidding.. Ned Carlson Triode Electronics,2225 W Roscoe Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun http://www.triodeel.com Text file catalogs:Catalog 'Bot at [email protected] Why 68K Input Resistors From [email protected] Tue Jul 21 10:01:51 CDT 1998 Article: 116933 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-newshub1.bbnplanet.com!news.bbnplanet.com!Supernews60!supernews.com!Supernews69!not-for-mail From: Randall Aiken Newsgroups: alt.guitar.amps Subject: Re: 68K input resistors, what purpose? Date: Mon, 20 Jul 1998 21:55:23 -0400 Organization: http://www.supernews.com, The World's Usenet: Discussions Start Here Lines: 52 Message-ID: <[email protected]> References: <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: 206.139.128.223 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: 900986226 HFL4NRM6I80DFCE8BC usenet78.supernews.com X-Complaints-To: [email protected] X-Mailer: Mozilla 3.0Gold (Win95; U) Xref: geraldo.cc.utexas.edu alt.guitar.amps:116933 [email protected] wrote: > > Here's a question for all you amp gurus, The resistor from the input jack to > the first grid of a tube amp, it's usualy 68K. I usualy see these in amps > with more than one input and have assumed that it's to give a lower level > input alternative. On Mesa boogies with one input there is no resistor here, > I've assumed this is because with only one input there's no need to provide a > lower level alternative. What I'd like to know is, are there other reasons > for that resistor? What would the reprocussions be to removing this resistor > and going straight from the input jack to the grid, (of course keeping the > 1Meg grid resistor), other than the one I've mentioned above? > > JKB > > -----== Posted via Deja News, The Leader in Internet Discussion ==----> http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum Those resistors are not just put on the control grid for signal level attenuation purposes; rather, they also act as a very high frequency low-pass filter in conjunction with the input capacitance of the triode (which is a sum of the grid-to-cathode capacitance and the Miller capacitance). This low-pass filter does a couple of things: (1) it helps prevent high frequency parasitic oscillation in the tube itself; (2) it helps prevent radio frequencies from getting into the input stage, where they can be rectified and lowpass filtered (AM detection) and become audible at the amplifier output; and (3) it can limit grid current when the tube is driven into the positive grid region. You will notice on two-input amps, such as Fenders, when you plug into the low-level input, the 1MEG grid resistor is shorted out and the two 68K resistors act as an attenuator to cut the input signal in half. The downside of this is that the input impedance drops from approximately 1MEG down to approximately 136K, which is a rather heavy load for a high impedance guitar pickup. If the resistor is connected in series with the input jack and before the 1MEG grid resistor, there is a small attenuation of the input signal (0.94 times). If the low-level input attenuation is not necessary, the resistor is best placed after the 1MEG grid resistor and should be soldered directly to the grid pin instead of back at the input jack. This will be the best position for RF and parasitic oscillation attenuation. Bottom line: leave it on there. Hope this helps, Randall Aiken [email protected] Why No More Cloth Wire From [email protected] Mon May 3 11:25:10 CDT 1999 Article: 176475 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer1.sprintlink.net!news.sprintlink.net!newspeer.gip.net!news.gsl.net!gip.net!news.voicenet.com!news3.voicenet.com.POSTED!not-for-mail Message-ID: <[email protected]> From: Rich Koerner Reply-To: [email protected] X-Mailer: Mozilla 3.04Gold (Win95; I) MIME-Version: 1.0 Newsgroups: alt.guitar.amps Subject: Re: Why carbon comp resistors and cloth wire? References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 27 Date: Sun, 02 May 1999 17:47:50 -0400 NNTP-Posting-Host: 207.103.135.116 X-Trace: news3.voicenet.com 925681474 207.103.135.116 (Sun, 02 May 1999 17:44:34 EDT) NNTP-Posting-Date: Sun, 02 May 1999 17:44:34 EDT Xref: geraldo.cc.utexas.edu alt.guitar.amps:176475 jgalt wrote: > > Does anyone know why carbon composition resistors are preferred for vintage > and reproduction amps? I thought metal film resistors are lower noise? This part I'll leave for the others in the News Group to respond to. > I don't understand how cloth wire effects things either. Well, the flow of electrons through the wire could care less what clothes the wire wears. :) However, the truth of the matter for Fender's discontinuation of the cloth wire in the amplifiers was due to environmental reasons. It was found that a fungus caused a type of jungle rot of the cloth in the South American exports. In some of those amplifiers, only the wire conductor was left of the original amplifiers wiring. Just one of the Fender moments in history I thought I'd share with the Group. Regards, Rich Koerner, Time Electronics. http://www.timeelect.com Why Silverface Changes From [email protected] Tue Aug 25 10:36:01 CDT 1998 Article: 123396 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!news.cis.ohio-state.edu!news.maxwell.syr.edu!nntp2.dejanews.com!nnrp1.dejanews.com!not-for-mail From: Admiral Ballsy Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Tue, 25 Aug 1998 02:29:22 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 40 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: 206.230.128.12 X-Article-Creation-Date: Tue Aug 25 02:29:22 1998 GMT X-Http-User-Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows 98) Xref: geraldo.cc.utexas.edu alt.guitar.amps:123396 In article <[email protected]>, In article <[email protected]>, > Charles Thomas wrote: > > I have a bit of a historical question. >> > > It seems to be almost unanimously believed that the "Blackface" pre-CBS Fender > > amplifiers sound light-years better than their Silverface counterparts (in > > cases when actual CBS wiring and component changes took place). >> > > What I'm wondering about was the thinking behind making these changes. Was it > > cheaper to make the amps the CBS way? Was there a shortage of parts, labor, > > know-how? Why would a company make changes to amps that are pretty > > universally recognized as being a bad idea? >> I think the changes can be lumped into several categories: 1. Make the amps clean - get rid of distortion. I believe that this is the motivation behind the changes to the inverter stage. 2. Fix problems caused by other changes. The PI changes also made the amps sound thin. The coupling caps from the PI to the output tubes were in most cases made larger, I think, to help remedy this. 3. Save money. The grid caps on the power tubes allowed sloppier (read: faster/cheaper) lead dress. The bias balance let Fender use unmatched tubes. 4. Increase reliability. I think that the reason the SF amps went to 5U4GB rectifiers is because good 5AR4s are a hell of a lot harder to make (read: expensive). 5U4GBs are a more rugged. Devotees of Euro GZ34s may argue, but an indirectly heated rectifier with such a low internal resistence is by nature difficult to accurately manufacture and more susceptible to shock-induced failure. AB -----== Posted via Deja News, The Leader in Internet Discussion ==----http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum From [email protected] Tue Aug 25 20:52:37 CDT 1998 Article: 123534 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!sunqbc.risq.qc.ca!torn!rover.ucs.ualberta.ca!news.ucalgary.ca!news From: Scott Hinman Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Tue, 25 Aug 1998 18:23:46 +0000 Organization: The University of Calgary Lines: 79 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: @plutonium.chem.ucalgary.ca Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0 (Macintosh; I; 68K) Xref: geraldo.cc.utexas.edu alt.guitar.amps:123534 Admiral Ballsy wrote: > I think the changes can be lumped into several categories: > > 1. Make the amps clean - get rid of distortion. I believe that this is the > motivation behind the changes to the inverter stage. Having black-faced a SF pro-reverb in steps, and tried really hard to be objective all along the way, changing the plate resistors in the PI section had very little effect, if any, on what I heard out of my amp. At the time, I thought it maybe got a little louder, but I didn't install switches to go back and forth. This wasn't a really scientific sort of test. (One day I'll go backwards with it and find out in more concrete terms what thats all about). > 2. Fix problems caused by other changes. The PI changes also made the amps > sound thin. The coupling caps from the PI to the output tubes were in most > cases made larger, I think, to help remedy this. The coupling caps in the BF amps (Super, Pro, Vibrolux, Twin, Deluxe) were 0.1 microFarad in the BF amps. They were the same value in the early SF amps. Did they change later on? Perhaps in conjunction with the master volume junk? > > 3. Save money. The grid caps on the power tubes allowed sloppier (read: > faster/cheaper) lead dress. I put switches in the grid caps on mine, and neither myself nor my wife could hear any diff. between swithching them in or out. Even during the middle of a loud sustained chord. (I also had it on a scope at the time to look for oscillation, which there was none of). I suspect that whether or not you hear any difference due to the grid caps depends on what speakers/guitar you may be using. For what its worth, the grid caps amount to installing a low pass filter with a cutoff frequency around 7 kHz. Most guitar speakers cutoff at around 5 kHz. > The bias balance let Fender use unmatched tubes. Well, yes. > > 4. Increase reliability. I think that the reason the SF amps went to 5U4GB > rectifiers is because good 5AR4s are a hell of a lot harder to make (read: > expensive). 5U4GBs are a more rugged. In fact, some of the models that originally had 5AR4/GZ34 went the other way. e.g. The BF AB763 Super Reverb had a GZ34 in it. The "dreaded" AB 568, with all of the worst of the CBS mods, went with the 5U4GB. Same with the Pro, and some others. They likely went to the 5U4 for cost reasons alone ( a guess on my part). In any event, the GZ34 is so close to solid state in performance, I don't why they didn't just stick diodes in there. (Which they were doing anyway with the BF Twin Reverbs). As far as the early SF amps went, the only big difference in sound that I heard when I BF'd my SF, was due to the partial cathode bias they threw in there. And even then, it was just because they didn't use a big enough bypass cap on the cathode resistors. When I did my amp, I rigged it with switches so I could short the cathode to ground (i.e. BF), or switch 200 microF caps in parallel with the cathode resistors, as opposed to the single 25 microF cap between the two cathodes that Fender(CBS) used. Couldn't tell the diff between the 200 mF caps in parallel with the cathode resistors, or just shorting the cathodes to ground. (Yes, I had a decade resistance box in there to let me adjust the bias to the same level within a matter of mseconds when I switched). Anyway, my take on it is that the whole BF/SF thing is a little overblown. (Of course, I'm talking early SF here, .. never played with any of the master volume stuff). People will argue with me, I know. But thats what my guitar and my speakers told me. Yours may differ. Best regards, Scott H. From [email protected] Wed Aug 26 11:10:51 CDT 1998 Article: 123615 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!usc!howland.erols.net!newsfeed.internetmci.com!204.238.120.130!news-feeds.jump.net!nntp2.dejanews.com!nnrp1.dejanews.com!not-for-mail From: Admiral Ballsy Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Wed, 26 Aug 1998 13:15:00 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 23 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: 12.6.251.18 X-Article-Creation-Date: Wed Aug 26 13:15:00 1998 GMT X-Http-User-Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows NT) Xref: geraldo.cc.utexas.edu alt.guitar.amps:123615 In article <[email protected]>, [email protected] wrote: > Admiral Ballsy wrote: > what thats all about). > > > 2. Fix problems caused by other changes. The PI changes also made the amps > > sound thin. The coupling caps from the PI to the output tubes were in most > > cases made larger, I think, to help remedy this. > > The coupling caps in the BF amps (Super, Pro, Vibrolux, Twin, Deluxe) > were 0.1 microFarad in the BF amps. They were the same value > in the early SF amps. Did they change later on? Perhaps in conjunction > with the master volume junk? Mea culpa! I meant that the PI INPUT coupling cap was made larger, .01 vs. .001 in most cases. This *does* have a noticeable effect, it lets a lot more bass through. Whether you like it or not it a matter of taste. AB -----== Posted via Deja News, The Leader in Internet Discussion ==----http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum From [email protected] Wed Aug 26 16:04:27 CDT 1998 Article: 123640 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!newspeer.monmouth.com!netnews1.nw.verio.net!netnews.nwnet.net!nnrp2.ni.net!not-for-mail From: "johng" Newsgroups: alt.guitar.amps References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> Subject: Re: Silverface.... WHY? Lines: 109 X-Newsreader: Microsoft Outlook Express 4.72.3155.0 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3155.0 Organization: Cyberverse, Inc. Message-ID: <[email protected]> Cache-Post-Path: [email protected] Cache-Post-Path: [email protected] Date: Wed, 26 Aug 1998 16:39:53 GMT NNTP-Posting-Host: 209.151.224.37 NNTP-Posting-Date: Wed, 26 Aug 1998 09:39:53 PDT Xref: geraldo.cc.utexas.edu alt.guitar.amps:123640 Scott Hinman wrote in message <[email protected]>... >Admiral Ballsy wrote: > >> I think the changes can be lumped into several categories: >> >> 1. Make the amps clean - get rid of distortion. I believe that this is the >> motivation behind the changes to the inverter stage. > >Having black-faced a SF pro-reverb in steps, and tried really hard >to be objective all along the way, changing the plate resistors >in the PI section had very little effect, if any, on what I heard >out of my amp. At the time, I thought it maybe got a little louder, >but I didn't install switches to go back and forth. This wasn't >a really scientific sort of test. (One day I'll go backwards >with it and find out in more concrete terms what thats all about). They do make a difference but mostly when the grid caps are still on the output tubes. The larger values raise the corner frequency of the high frequency rolloff. They will approximately double the gain of the phase splitter as well. >> 2. Fix problems caused by other changes. The PI changes also made the amps >> sound thin. The coupling caps from the PI to the output tubes were in most >> cases made larger, I think, to help remedy this. > >The coupling caps in the BF amps (Super, Pro, Vibrolux, Twin, Deluxe) >were 0.1 microFarad in the BF amps. They were the same value >in the early SF amps. Did they change later on? Perhaps in conjunction >with the master volume junk? I think he was talking about the couple cap to the *input* of the phase splitter here. The cap change is always coupled with changing the grid resistors. 1Meg/.001uF vs. 330K/.01uF. The 330K/.01uF lowers the frequency response of the input to the PI. I found that the increase lower frequencies getting to the output stage in a DR will cause it to start distorting a lot earlier that it would with the BF values. >> 3. Save money. The grid caps on the power tubes allowed sloppier (read: >> faster/cheaper) lead dress. > >I put switches in the grid caps on mine, and neither myself nor my >wife could hear any diff. between swithching them in or out. Even >during the middle of a loud sustained chord. (I also had it on >a scope at the time to look for oscillation, which there was none >of). I suspect that whether or not you hear any difference due to >the grid caps depends on what speakers/guitar you may be using. >For what its worth, the grid caps amount to installing a low pass >filter with a cutoff frequency around 7 kHz. Most guitar speakers >cutoff at around 5 kHz. 7KHz? with 47Ks in the PI, the impedance of a 1200pF capacitor (not all grid caps are 1200pF, but mine were) in parallel with the 220K grid bias resistors is 47K at 2.2KHz. The gain of the PI section is half of its unloaded value at this point because the 47K load is in parallel with the plate resistors. At lower frequencies, the cap is a higher impedance and the load becomes dominated by the 220k grid bias resistors. Without the caps, the load on the plates is 220K all the time. I don't see where you came up with 7KHz? With the plate resistors at 82K/100K, this point occurs when the impendance of the capacitor (in parallel with the 220K) is equal to ~82K. This occurs at ~1KHz, which is why they probably changed to the 47Ks in the first place. If you have a decent quality speaker in there, the difference is *very* noticable. >> The bias balance let Fender use unmatched tubes. > >Well, yes. >> >> 4. Increase reliability. I think that the reason the SF amps went to 5U4GB >> rectifiers is because good 5AR4s are a hell of a lot harder to make (read: >> expensive). 5U4GBs are a more rugged. > --Rectifier toob stuff snipped out-> >Anyway, my take on it is that the whole BF/SF thing is a little >overblown. (Of course, I'm talking early SF here, .. never played >with any of the master volume stuff). People will argue with me, >I know. But thats what my guitar and my speakers told me. Yours >may differ. Did you change the speakers to match? If not, you really only did half of the BF mod. Some of the changes (input to the PI) were made, IMHO, to compensate for the lack of low-frequency response of the Oxford and Utah speaker they were using at the time. If you don't have a 'Jensen' style speaker(e.g. Webers or Naylors), you're not going to hear the majority of the difference. I have done both a 74 Deluxe Reverb and a 76 Pro Reverb of my own and the differences were incredible. I would call it the difference between 'alive' and 'sterile'. That's my experience. --john greene From [email protected] Wed Aug 26 16:04:43 CDT 1998 Article: 123663 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.eng.convex.com!newsgate.duke.edu!newsfeed.berkeley.edu!newsfeed.axxsys.net!newsfeed.internetmci.com!209.150.160.22!newsfeed.wli.net!208.10.192.30!nntp2.dejanews.com!nnrp1.dejanews.com!notfor-mail From: Admiral Ballsy Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Wed, 26 Aug 1998 20:13:26 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 34 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: 12.6.251.18 X-Article-Creation-Date: Wed Aug 26 20:13:26 1998 GMT X-Http-User-Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows NT) Xref: geraldo.cc.utexas.edu alt.guitar.amps:123663 In article <[email protected]>, "johng" wrote: >> > >The coupling caps in the BF amps (Super, Pro, Vibrolux, Twin, Deluxe) > >were 0.1 microFarad in the BF amps. They were the same value > >in the early SF amps. Did they change later on? Perhaps in conjunction > >with the master volume junk? > > I think he was talking about the couple cap to the *input* of the phase > splitter here. The cap change is always coupled with changing the grid > resistors. 1Meg/.001uF vs. 330K/.01uF. The 330K/.01uF lowers the frequency > response of the input to the PI. I found that the increase lower frequencies > getting to the output stage in a DR will cause it to start distorting a lot > earlier that it would with the BF values. > AB: Yup, I was. But not all amps got the 330K; for example, Supers got the .01 cap, but kept the 1M resistors. > Did you change the speakers to match? If not, you really only did half of > the BF mod. Some of the changes (input to the PI) were made, IMHO, to > compensate for the lack of low-frequency response of the Oxford and Utah > speaker they were using at the time. If you don't have a 'Jensen' style > speaker(e.g. Webers or Naylors), you're not going to hear the majority of > the difference. AB: Speaker changes weren't an across-the-board thing. Again, using the Super as an example, I've seen the same alnico CTS speakers in amps dating >from '65 up to '73. -----== Posted via Deja News, The Leader in Internet Discussion ==----http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum From [email protected] Wed Aug 26 21:08:14 CDT 1998 Article: 123678 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.cs.utah.edu!dog.ee.lbl.gov!newsfeed.berkeley.edu!su-news-hub1.bbnplanet.com!news.bbnplanet.com!logbridge.uoregon.edu!scanner.worldgate.com!rover.ucs.ualberta.ca!news.ucalgary.ca!news From: Scott Hinman Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Wed, 26 Aug 1998 12:30:18 +0000 Organization: The University of Calgary Lines: 21 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> Reply-To: [email protected] NNTP-Posting-Host: @plutonium.chem.ucalgary.ca Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 2.0 (Macintosh; I; 68K) Xref: geraldo.cc.utexas.edu alt.guitar.amps:123678 Scott Hinman wrote: > > Admiral Ballsy wrote: > > > 4. Increase reliability. I think that the reason the SF amps went to 5U4GB > > rectifiers is because good 5AR4s are a hell of a lot harder to make (read: > > expensive). 5U4GBs are a more rugged. > > In fact, some of the models that originally had 5AR4/GZ34 went the > other way. e.g. The BF AB763 Super Reverb had a GZ34 in it. The > "dreaded" AB 568, with all of the worst of the CBS mods, went with > the 5U4GB. Same with the Pro, and some others. They likely went > to the 5U4 for cost reasons alone ( a guess on my part). Oops! Obviously it was pretty late when I wrote this. I didn't really say anything different than you did. I think what I was getting at (who knows for sure) was that some of the early SF's (like my AB668 Pro Rev.) retained the GZ34. They didn't move to 5U4 till AA1069. Sorry for the confusion. Regards. Scott H. From [email protected] Thu Aug 27 09:04:31 CDT 1998 Article: 123764 of alt.guitar.amps From: [email protected] (Bill Bolton) Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Thu, 27 Aug 1998 10:49:04 GMT Reply-To: [email protected] (Bill Bolton) Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> X-Newsreader: Forte Agent 1.5/32.451 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 139.134.96.93 Lines: 26 Path: geraldo.cc.utexas.edu!cs.utexas.edu!nntpX.primenet.com!nntp.primenet.com!news.maxwell.syr.edu!intgwpad.nntp.telstra.net!nsw.nntp.telstra.net!139.134.5.33!139.134.96.93 Xref: geraldo.cc.utexas.edu alt.guitar.amps:123764 Admiral Ballsy wrote: > I think the changes can be lumped into several categories: > > 1. Make the amps clean - get rid of distortion. I believe that this is the > motivation behind the changes to the inverter stage. As has been demonstrated previously in this newsgroup, the BF phase splitter actually runs the tubes outside of specification. The SF phase splitter changes runs them within their specification. Its my opinion that give the various recorded statements about the overall profile of Fender's warranty experience with their amps as production volumes increased, many (though not all) of the changes that were made simply in response to both perceived and real issues which would potentially reduce warranty costs. Given that Leo never again became involved in amplifiers after leaving Fender and seemed to be quite content to work on instruments, its arguable that a number of amp changes would have occurred whether Fender had been sold or continued under its former ownership. Cheers, Bill From [email protected] Fri Aug 28 09:45:45 CDT 1998 Article: 123873 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!novia!sequencer.newscene.com!not-for-mail From: [email protected] (Ned Carlson) Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: 27 Aug 1998 23:38:18 -0500 Organization: Triode Electronics Lines: 35 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> Reply-To: [email protected] X-Newsreader: Forte Free Agent 1.11/32.235 Xref: geraldo.cc.utexas.edu alt.guitar.amps:123873 On Thu, 27 Aug 1998 16:17:24 GMT, "johng" wrote: >I don't recall reading any discussion about the phase splitter running >outside of specification. I'll search DejaNews to see if I can find anything >but right now I can't think of how reducing the plate resistors would >improve anything as far as operating point is concerned. I think what he's referring to is the fact that the 220K grid resistors on the output tubes are indeed higher than what's spec'd for maximum DC grid circuit resistance on a 6L6, with fixed bias. Good 6L6's will indeed work with a 220K grid resistors, but cutting the value back to 100K means one needn't be quite as picky about tubes. I imagine (and in fact I've of similar things happening in the TV industry) that the people who supplied the tubes may not have wanted to take duds back if the tubes were used like that, or Fender was rejecting tubes that wouldn't work right with the 220K resistor, and the supplier complained, or maybe it was some CBS dork who saw that the value was out of spec & insisted it be changed, whether it needed it or not. Ned Carlson Triode Electronics "where da tubes are!" 2225 W Roscoe Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun http://www.triodeel.com Your Start Page for Tube and Tube Amp info on the net... http://www.triodeel.com/tlinks.htm From [email protected] Mon Aug 31 09:12:20 CDT 1998 Article: 124200 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!howland.erols.net!panix!news.panix.com!not-for-mail From: [email protected] (Mark Garvin) Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: 31 Aug 1998 03:08:02 -0400 Organization: PANIX Public Access Internet and Unix, NYC Lines: 51 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]> NNTP-Posting-Host: panix2.nfs100.access.net X-Newsreader: NN version 6.5.1 (NOV) Xref: geraldo.cc.utexas.edu alt.guitar.amps:124200 >Scott Hinman wrote in message <[email protected]>... >>Having black-faced a SF pro-reverb in steps, and tried really hard >>to be objective all along the way, changing the plate resistors >>in the PI section had very little effect, if any, on what I heard >>out of my amp. At the time, I thought it maybe got a little louder, > "johng" writes: >They do make a difference but mostly when the grid caps are still on the >output tubes. The larger values raise the corner frequency of the high >frequency rolloff. They will approximately double the gain of the phase >splitter as well. John, True that gain can *theoretically* be increased by raising plate resistance, with a perfect current source approaching the tube's mu. A couple things to consider, though: First, loading of subsequent stages will defeat the purpose of using a current source plate load. The bias supply resistors will load the circuit anyway -- even if there were something to be gained by keeping plate impedance that high. BTW, the bias supply resistors are the component that operates the output tubes out of spec: High values possibly causing tubes to 'go gassy' or even fail with (somewhat obscure) latchup modes. Second, the increase in gain is not linear with respect to the plate res value. The delta in gain slows after the plate load surpasses the tube's plate resistance. A 12at7's plate res is low enough that the silverface->bf change will not yield anywhere close to a 2:1 improvement. In fact, the gain of the Fender silverface split tail circuit is already fairly high, so I'd expect a couple db or so. A tube with high plate res (12ax7) would show much more variation in gain, of course. >7KHz? with 47Ks in the PI, the impedance of a 1200pF capacitor (not all grid >caps are 1200pF, but mine were) in parallel with the 220K grid bias >resistors is 47K at 2.2KHz. The gain of the PI section is half of its >unloaded value at this point because the 47K load is in parallel with the >plate resistors. At lower frequencies, the cap is a higher impedance and the >load becomes dominated by the 220k grid bias resistors. Without the caps, >the load on the plates is 220K all the time. I don't see where you came up >with 7KHz? I believe it was already pointed out that the 12at7's plate resistance is part of the source impedance equation. The rp is probably around 11k. MG From [email protected] Tue Sep 1 10:42:13 CDT 1998 Article: 124341 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!news.maxwell.syr.edu!news-peer.gip.net!news.gsl.net!gip.net!portc01.blue.aol.com!audrey03.news.aol.com!not-for-mail From: [email protected] (LarrySB) Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Lines: 20 Message-ID: <[email protected]> NNTP-Posting-Host: ladder03.news.aol.com X-Admin: [email protected] Date: 1 Sep 1998 03:51:02 GMT Organization: AOL http://www.aol.com References: <[email protected]> Xref: geraldo.cc.utexas.edu alt.guitar.amps:124341 >Not in all SF amps. Look at the Twin - the plate voltages drop by over >50V at >the change to SF. I was looking at one the other day in fact, and the actual plate B+ was 496V. The AA769 Schematic (from Pittmans book) does show 410v, which is a drop from the AB763 schematic. That would support you contention about the earliest Silverface Twins. However, every other version of the Solverface Twin shows ever increasing power supply voltages. Every other model of Silverface amp shows a marked increase in B+ voltage, especially in the later years. -Dr. Nuketopia Compiling at this very moment. Read the Blue Glow in Tubes FAQ at http://www.persci.com/~larrysb Please note that your email is *not* spam in the subject line. From [email protected] Tue Sep 1 10:42:27 CDT 1998 Article: 124401 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!math.ohio-state.edu!news.cis.ohio-state.edu!news.maxwell.syr.edu!news-nyc.telia.net!news.idt.net!newsfeed.internetmci.com!204.238.120.130!newsfeeds.jump.net!nntp2.dejanews.com!nnrp1.dejanews.com!not-for-mail From: Admiral Ballsy Newsgroups: alt.guitar.amps Subject: Re: Silverface.... WHY? Date: Tue, 01 Sep 1998 14:03:15 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 30 Message-ID: <[email protected]> References: <[email protected]> <[email protected]> NNTP-Posting-Host: 12.6.251.18 X-Article-Creation-Date: Tue Sep 01 14:03:15 1998 GMT X-Http-User-Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows NT) X-Http-Proxy: 1.0 x7.dejanews.com:80 (Squid/1.1.22) for client 12.6.251.18 Xref: geraldo.cc.utexas.edu alt.guitar.amps:124401 In article <[email protected]>, [email protected] (LarrySB) wrote: > >Not in all SF amps. Look at the Twin - the plate voltages drop by over > >50V at > >the change to SF. > > I was looking at one the other day in fact, and the actual plate B+ was 496V. > > The AA769 Schematic (from Pittmans book) does show 410v, which is a drop from > the AB763 schematic. That would support you contention about the earliest > Silverface Twins. > > However, every other version of the Solverface Twin shows ever increasing power > supply voltages. > > Every other model of Silverface amp shows a marked increase in B+ voltage, > especially in the later years. When the MV came along, yes. But the AA270 circuit shows 405V; note also that the power supply resistors between the 20mfd filters got larger, too, further lowering preamp B+. FWIW, I've got a '71 on the bench now that runs ~440V, ref my '65 that runs about 480V. AB diy From [email protected] Sat Mar 6 11:06:20 CST 1999 Article: 163427 of alt.guitar.amps Path: geraldo.cc.utexas.edu!cs.utexas.edu!howland.erols.net!newsfeed.cwix.com!207.207.0.26!nntp.giganews.com!nntp2.dejanews.com!nnrp1.dejanews.com!notfor-mail From: [email protected] Newsgroups: alt.guitar.amps Subject: Re: Three Prong courtesy outlet? Date: Sat, 06 Mar 1999 13:46:51 GMT Organization: Deja News - The Leader in Internet Discussion Lines: 26 Message-ID: <[email protected]> References: <01be6600$a860c560$5ea100d8@default> <[email protected]> <01be66a9$07c045a0$5ea100d8@default> NNTP-Posting-Host: 198.4.94.180 X-Article-Creation-Date: Sat Mar 06 13:46:51 1999 GMT X-Http-User-Agent: Mozilla/4.08 [en] (Win95; U ;Nav) X-Http-Proxy: 1.0 x4.dejanews.com:80 (Squid/1.1.22) for client 198.4.94.180 Xref: geraldo.cc.utexas.edu alt.guitar.amps:163427 In article <01be66a9$07c045a0$5ea100d8@default>, "Dean Yiapis" wrote: > OK Thanks LV! > I'll check around s'more and let everyone know what I find. > -> Dean > > And yet another person annoyed by spam, remove > the not_here from my address to reply. > > Lord Valve wrote in article > <[email protected]>... > > Lord Valve Speaketh: > > Yeah, Amphenol makes (used to make?) a three-hole outlet which > > is the exact same size as the existing one. I found a shitload > > of 'em surplus, once, at around a buck apiece. After I used 'em > > all up, I tried to buy some more...and the new price was more > > than TEN BUCKS a pop. From Newark, I believe, and this was > > ten years ago. I don't know what the situation is currently > > on these, but if you find any as surplus, snap 'em up! >> I use a NEMA 5-15R single receptacle made by Leviton, Eagle, etc. Electrical supplies house at about $1.35 last time I bought some. -----------== Posted via Deja News, The Discussion Network ==---------http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
