Download PSUD2 Help.pdf

Wednesday, February 20, 2002 12:52:23 PM
From:
Mark Lavelle ([email protected])
Date: 2/20/2002 6:26 AM
Subject:
PSUD2 Help?
Duncan's PSU Designer II is a great little tool, but I'm still puzzled about a few aspects:
1. How do I properly determine the 'off-load voltage' and 'source resistance' of the PT? I
know he provides calculators for this purpose, but I've never seen 'regulation' in a
Hammond spec. If I already have the PT in hand, am I better off just plugging it into the
wall and reading the RMS AC?
2. How do I know what value to plug in for the Load block? It's obvious that it depends
on the rest of the circuit, but how?
Thanks heaps...
From:
kg
Date: 2/20/2002 1:53 PM
Subject:
Re: PSUD2 Help?
off load voltage is just that, output voltage with no load on the secondary. i THINK
hammond rates their output voltage WITH load (not sure though), so you might have to
have one in hand to get it right. it will always be more accurate with real life
measurements.
source resistance is pretty much the DCR of the 2ndary. that will work well enough.
the load resistance is the equivalent resistance... say you had a 2xel34 running at
500vdc and 20 mA per tube... that's 40 mA total @ 500vdc, so v/i = r, and 500v/0.04 =
12k5. under full load, if you expect it to pull 100mA per tube, then it would be 500v/0.2 =
2k5.
hth
ken
From:
Mark Lavelle ([email protected])
Date: 2/20/2002 5:48 PM
Subject:
Re: PSUD2 Help?
Thanks, Ken. I think Hammond uses the loaded voltage, too. Guess I'll have to check
that tonight...
On calculating the load: Am I correct in assuming that you only mention the power tubes
because the preamp tubes are insignificant in comparison? Does that still hold true in a
very low power (let's say under 3W) design?
1 of 2
Wednesday, February 20, 2002 12:52:23 PM
From:
kg
Date: 2/20/2002 6:50 PM
Subject:
Re: PSUD2 Help?
for best results include all of the load currents. in a 100w amp, the preamp is
insignificant, but not so in a low power amp, as you surmised.
ken
From:
Geoff Gross ([email protected])
Date: 2/20/2002 7:32 PM
Subject:
Re: PSUD2 Help?
Instead of using the resitive load to simulate your tubes' current draw, use a current
source. You can add as many of these as you want, and you can place them anywhere
in the ps chain. IIRC, you must have the resistive load at the end of the chain, which
would most likely be the wrong place to put your power tubes. I use the resistive load
only to simulate the last preamp tube on the chain (usually around 300k or so for 1mA),
and use current sources to simulate everything else, placing them at the appropriate
spot in the power supply.
Geoff
From:
Mark Lavelle ([email protected])
Date: 2/20/2002 8:50 PM
Subject:
Re: PSUD2 Help?
So that's what the "current tap" modules are for! Should be a lot easier to ballpark that
than calculating the load.
Ya know, if I hang out here at Ampage for a few more years I might eventually
understand what I'm doing (does that take all the fun out of it?)! Scary, huh?
Thanks again, guys...
2 of 2