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AA AUDiO ALTO Dual mono integrated hybrid amplifier Model DMI 3 H User Manual WITHIN THE BEAUTY OF SOUND Version 1.0 www.audioalto.com [email protected] AUTHOR AND FOUNDER FOREWORD Dear customer, Let me express my thankfulness for granted trust in buying Audio Alto’s product. AA DMI 3 H is part of Audio Alto family products. All my products follow our philosophy. At Audio Alto we strive not only to achieve perfect reproduction of sound that preserves all the purity, openness, width and depth of the original but we also aim for aesthetic perfection and this “Compact series” product confirms it. Our entire electronic product family follows the same concepts: all voltage amplifying circuits are class A topology and some of them are also single ended. I also believe that vacuum tubes as voltage amplifying components deliver the most natural and detailed sound reproduction. The vacuum tube is also capable of amplifying the analog audio signal without using global negative feedback and maintaining the required linearity. To achieve the same linearity with solid state topology many more components must be involved, meaning that the audio signal must pass through them. With triode amplification only one capacitor and three resistances are involved so the signal is much closer to the amplified original. I believe that the use of global negative feedback (GNFB), especially in the power amplifier that drives the speaker, lowers the openness, naturalness and micro details that most of the music is made from. Most producers and technical reviewers, while testing power amplifiers, use artificial passive load (made of resistances, impedances and capacitances) but the speakers that the amplifiers are driving are somehow “live” loads. The speaker (the build in driver) generates induced voltage as a result of the cone movement in the magnetic field. Part of this voltage, which holds (mostly unpleasant) information of the speaker box and ambient reflections, is projected through GNFB to the input of the power amplifier. In reality this induced voltage should (must) be ignored and shouldn’t be (re)amplified again and transferred back to the speaker, generating new induced voltage that returns back to the amplifier input and so on… Using GNFB lowers development and production costs and is somehow a must in large(r) scale production. As my products are produced in small quantities and mostly upon customer orders (requests) Audio Alto can follow the more difficult path in developing producing audio products that sound "correct" (compared to the more widespread commercial products). To fulfill this concept all parts of the amplifying circuits must be chosen and tested before installed as there is no active GNFB correction of the parts and their linearity problems. As Audio Alto products DO NOT USE GNFB, the amplifiers output impedance is usually higher (the damping factor (DF) is lower). I do believe that this approach gives the speakers the ability to perform and deliver to the listener openness, naturalness and micro details as the listener is expecting. Audio Alto speakers are designed so that their box Q factor (box damping) is correct per se without requiring the driving capabilities of the attached amplifier (“usually” it’s a high damping factor). AA DMI 3 H includes all the previously mentioned concepts. Its DF is 15 for optimal (well designed) speaker driving, but the user can also select a DF = 50 for less damped speakers. It also includes a new practical way of correcting speaker response (called TILT – as was introduced in the year 1982 - in a Quad preamplifier). I’m confident that the reproduction it will give you is very natural and pleasant and that it will give you many years of listening pleasure. Yours sincerely, Sasha Burian © by www.audioalto.com 2 AA DUAL MONO INTEGRATED HYBRID AMPLIFIER USER MANUAL We are sure that you will derive many years of listening pleasure with your new AA DMI 3 H dual mono integrated amplifier. These approaches give the AA DMI 3 H a remarkably natural, detailed, open reproduction and provide great stage sound. This brief operating manual contains important information regarding the operation and care of the amplifier, so be sure to read this manual carefully and follow these simple instructions in order to keep it looking, operating and sounding its best! © by www.audioalto.com 3 SAFETY PRECAUTIONS IMPORTANT SAFEGUARDS PLEASE READ CAREFULLY ALL THE FOLLOWING IMPORTANT SAFEGUARDS THAT ARE APPLICABLE TO YOUR EQUIPMENT CAUTION! TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE SCREWS. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL. SAFETY 1) Read the User’s Manual and refer to it frequently during use of this product - All the safety and operating instructions should be read before the product is operated. 2) Retain the User’s Manual - The safety and operating instructions should be retained for future reference. 3) Follow Instructions - All operating and instructions for use should be closely followed. 4) Power Sources - This product should be operated using only the type of power source indicated on the marking label. If you are not sure of the type of power supply in your home, consult your product dealer or local power company. 5) Grounding - This product is equipped with a three prong IEC connector. Always use power cord with adequate wire cross section and an electrical outlet that is grounded. If you do not know whether the outlet is grounded, consult your electrician or local power company. 6) Power Cord Protection – Power supply cords should be routed so that they are not likely to be walked on or pinched. Pay particular attention to cords at plugs, convenience receptacles and where they exit from the product. Always use power cords with adequate current ratings and safety certifications (UL, CE, TÜV, CSA, etc.) 7) Fuses - For continued protection against fire hazard, replace fuses with the same type and rating of the fuses specified. When changing fuses, completely unplug the AC cord from the wall outlet. 8) Vacuum Tubes - During operation the tubes get very hot. Do not touch the tubes since this may result in a severe burn. Allow at least 10 minutes after removing power for tubes to cool down before touching them. 9) Turn-off when not using - Turn off the unit as you stop actively using it. Unplug the power supply from the wall during a lightning storm or when the product is to be left unattended and unused for longer periods of time. ENVIRONMENT 1) Water and Moisture - Do not use this product near water - i.e. near a bathtub, ash bowl, kitchen sink or laundry tub; in a wet basement; or near a swimming pool or the like. Damp basements should be avoided. 2) Heat - The product should be situated away from heat sources such as radiators, heat registers, stoves or other appliances that produce heat. Also avoid putting the unit in the direct rays of the sun. 3) For indoor use only. © by www.audioalto.com 4 PLACEMENT 1) Accessibility - It is normal for a vacuum tube power amplifier to run warm if used for prolonged periods. 2) Ventilation - This product should not be placed in a built-in installation or rack unless proper ventilation is provided or the manufacturers' instructions have been followed. Never place anything on top your amplifier that could obstruct the airflow and cause the electron tubes to overheat and damage the amplifier. Do not place your amplifier in a closed bookcase; overheating could occur. Ensure that there is at least 100mm (4 inches) of open space above the amplifier. 3) Surface - Place the unit on a flat level surface. Care should be taken to prevent objects from falling and liquids from spilling into the unit. Do not subject the unit to excessive smoke, dust, vibration or shock. VACUUM TUBES The vacuum tubes are installed inside the amplifier case and are not directly accessible without removing the bottom cover. You should not remove the cover. The cover should be removed by qualified personnel only. The tubes have 6 month warranty. Handling We suggest that you do not handle the tubes with your bare hands or fingers as skin oils deposited on the glass surface can “leach” through the glass envelope and cause the tube to become “gassy.” In other words, your tube life may be shortened unnecessarily. Use a paper towel or one of the cotton gloves (supplied) instead. This is also the recommended procedure for handling the small input tubes. Installation The tubes should be changed by qualified personnel. To access the tubes you need to remove the bottom cover unscrewing all the screws visible on the bottom cover. Whenever you remove or insert the tubes into their sockets, handle them gently and do not force them into the sockets. Instead, “rock” them slightly as you slowly push them into place, making sure that they are properly seated. Recommended Tube Types Your AA DMI 3 H amplifier is supplied from the factory with EH 6922 (E88CC or 6DJ8 NOS) tubes for line driver stage (depends on model options). The tubes are installed inside the amplifier enclosure (visible from the top and from side). The estimated working time for the tubes is between 5.000 to 6.000 hours. © by www.audioalto.com 5 DESIGN DESCRIPTION The AA Compact series aesthetics and elegant look was a (hard) task to achieve, especially when taken into consideration that all models use tubes as voltage amplification and that some of them weight up to 25kg. The enclosure is made of extruded, CNC machined, 10mm thick aluminum (or brass in chromed version). This panel covers and enforces the internal aluminum cage. The approach gives completely acoustically inert and damped enclosure. Each channel, main power and control section are separated by internal aluminum walls and enclosed in a so called Faraday cages for noise and interference reduction. The result of this is a concept that combines strength and acoustic stability with a minimalistic and elegant outer appearance looking minimalistic and elegant. The AC power supply passes through the noise π (pi) filter and a DC blocker that eliminates the DC voltage that can eventually be present in the main power line that can cause transformers to buzz. The power supply uses two 150VA toroidal transformers with electrostatic shield and magnetic screen (for each mono section one). Voltage smoothing is achieved with 2 banks of 4 low ESR electrolytic capacitors with total capacity of 2x 19.000uF. The capacitors are smaller (but just in dimensions) than usually used with the benefit of lower impedance. The special circuit lowers the mains ripple by additional 6dB but more importantly attenuate the higher frequency noise much more. With the addition of metal film high grade capacitors this approach eliminates also the so called insulation discharges, thus enhancing the naturalness and details of the reproduced sound. All supply voltages sources and circuits are doubled (dual mono), the voltages are regulated and are time and amplitude delayed for smoother power up thus protecting the vacuum tube. The tube heater voltage starts at 1V and gradually in 6 seconds reaches the nominal amplitude of 6,3V. As the tube gets hot the high voltage starts to gradually rise from 0V up to the nominal amplitude (it takes around 120 seconds to reach the required amplitude). This way the tubes life span is prolonged to well over 5.000 hours. All the internal voltage amplifier stages work in Class A mode of operation. The input stages are realized with low noise low distortion circuits and are also working in class A mode. The voltage amplification is realized with a double triode vacuum tube configured in CCDA (Constant Current Draw Amplifier) single ended topology to eliminate the supply voltage fluctuations due to audio signal changes. The selected tube 6922 or E88CC (NOS 6DJ8) are among the best audio triodes providing low input capacity, high standby current, low output impedance and very low distortion levels even without negative feedback. The tube glass is dumped with a special silicone ring. A complementary MOSFET output transistor transforms the CCDA output with output impedance of few hundreds of ohms to low impedance (high current) output required by speakers. The output transistors are biased with an innovative dedicated circuit that keeps both output transistors biased during the whole signal phase (360°) reducing the low power related distortions (no typical class A/B turn off that is the cause of unpleasing crossover distortion). The circuit significantly reduces the distortion caused by the effects of nonlinear transconductance in the output transistors resulting in a sound almost identical as it would be produced with an pure class A output stage. The voltage and current amplifiers work without any global negative feedback! © by www.audioalto.com 6 All capacitors used in the audio path and blocking positions are high grade metal film polypropylene Wima (MKP4 and MKP10). Volume regulation is realized with Blue Alps motorized potentiometer. All resistors are metal film 1% (excluded high power resistors). The wiring is done with OFC (oxygen free) copper cables, all connectors are high grade gold plated. Signal switching is performed with 16 high grade completely closed signal relays (with silver plated contacts). The additional functionality of the input select relays is to completely isolate the unused source from the input of the amplifier (including the common pin – ground). Benefits of this approach are lower crosstalk between the channels and removal of the potential ground loops between different attached sources, thus lowering noises and input hum. Input Phono/I1 can be configured for line or phono (RIAA) input moving magnet (MM) sensitivity (moving coil MC can be also ordered). The phono preamplifier is optional and can be ordered and installed separately. The circuit topology compared to widely used circuits is innovative with two amplifiers working in parallel. This configuration lowers the distortion and noise. The amplifiers are working in class A mode and also providing high current driving capabilities that the low noise RIAA equalization needs. The power supply for the amplifier is additionally filtered with the intention to eliminate the noise and internal insulation discharges. The sound of the phono amplifier is remarkably natural, open and detailed. The digital control logics (including the radio frequency remote control1) are designed as not active (static) while not in use, so no disturbing noises can degrade the listening process. The control logic is also electrically isolated and optically separated. The assembly of the unit is handmade; all components are tested for functionality and tolerances before being installed. All these approaches give the AA DMI 3 H a remarkably detailed, natural, open reproduction and provide great stage sound. We are sure that such approach in design and building will give our customers great satisfaction while using and enjoying the music for many years! 1 - separately ordered © by www.audioalto.com 7 AA DMI 3 H with radio remote controller © by www.audioalto.com 8 OPERATION FRONT panel POWER (STANDBY/OPERATE) Key On the right front panel of the amplifier, you will find a push button switch which controls the operating mode of the amplifier. In standby mode the LED above the button is red color. After pressing the button the LED changes to blue color and flashes for app. 45 seconds. During this time the tubes are heated. When LED stops flashing the amplifier is ready to reproduce sound program. INPUT Key On the front panel of the amplifier on the left side, you will see a push button switch which selects one of 3 inputs. Inputs are single ended (RCA) inputs. If the amplifier has the phono RIAA module installed the first input (LED) indicates this input. TAPE Key On the front panel of the amplifier, near the Volume knob, you will see the push button switch which selects Tape Monitor Input. MUTE Key On the front panel of the amplifier, you will see a push button switch labeled MUTE. This is used to MUTE the input signal. The primary use of this switch is to allow the user to remove (or connect) INPUT interconnects cable from the amplifier, preamplifier (or signal source) without the need to “power down” the amp. This feature will prevent “speaker destroying” bangs, hums, buzzes and thumps from being passed through the amplifier during these cabling changes. The Mute key operates on the output protection relay. VOLUME Knob On the front panel of the amplifier, you will see a round knob which regulates the volume of the sound program. Turning the knob clockwise increases the volume of the sound program. The knob has a light indicator that helps the user to determine the knob position. The light is on while the knob is remotely moved, after the knob stops the light is smoothly reduced to a lower density. PHONES jack On the front panel of the amplifier, on the right of the panel, you will see the phones jack (6,3mm). Inserting the phones jack mutes the amplifier speaker outputs. NOTE: All functions on the front panel are available through the radio remote unit. © by www.audioalto.com 9 REAR panel On the rear panel there are two sets of input/output connectors. The right side – red RCA connectors (left from front view), are connector and controls for the left channel. The left side – black RCA connectors (right from front view), are connector and controls for the right channel. In the middle of the panel there are the power IEC connector, the fuse holder, main On/Off switch, the ground connector (usually used for turntables, the switch (above the On/Off switch) to change the output impedance (for both channels), the Balance Knob and the connector for remote output operation functionality. The number of input – output connectors depends on the model ordered options. INPUTS/OUTPUTS Functionality is duplicated on the left and right side of the panel and is mirrored symmetrical. 1. I1/MM input is input 1 (LED on the front panel) and can be a line input (sensitivity 200mVeff) or if the phono module is installed is a phono RIAA input with 2mVeff sensitivity. 2. Filter on switch – toggle the switch “Up” enables first order high pass filter (rumble filter) for the phono Moving Magnet (MM) input to comply with IEC RIAA standard. The cut off frequency is 20Hz/-3dB. 3. I2 – Line 2 input. The input is intended for CD players and is less sensitive than I3 input. The sensitivity is 500mVeff. 4. I3 – Line 3 input. The sensitivity is 200mVeff. 5. Tape in – used as input with the same sensitivity as I3 input. It can be used with any device. If used with Tape devices (or other devices with Monitor functionality) the Tape out output should be used. 6. Tape out – used to output the selected sound program (not affected by Volume control). Output is not buffered and not attenuated. 7. Speakers outputs - 4mm Binding Posts. The speaker impedance should be between 4 and 8 Ohms. 8. Tilt on switch - used to enable or disable the Tilt Knob situated near the switch. 9. Tilt Knob – regulates the frequency response in a balance mode. Turning the knob clockwise increases the high frequency signal and simultaneously reduces low frequency signal by the same amount. Turning the knob counterclockwise increases the low frequency signal and simultaneously reduces high frequency signal by the same amount. Signal at 1.000Hz is not modified. The maximum increase/reduction is ±5dB. © by www.audioalto.com 10 REMOTE antenna input (optional) Remote antenna is needed to receive the commands from the radio remote control unit (supplied – 43mm long wire with jack). The antenna should be connected to the round connector marked with the BLACK DOT. REMOTE Receiver Antenna (optional) At the back of the enclosure the 173mm antenna is attached to a small connector for stronger and better receptions of remote commands. REMOTE output (optional) Remote output provides remote voltage source (12V/100 mA). While amplifier is turned “ON”, the voltage of 12V is present. POWER IEC connector On the rear panel in the middle you will see an IEC power connector. You can connect the amplifier to 230/240 (or 110/120) V A.C. wall socket with the appropriate cable. The connector also holds a Fuse holder and On/Off switch. You can extract the fuse with a screwdriver. There is also a spare fuse. Replace the fuse only with the same current ratings fuse. ON/OFF switch The On/Off switch is a mains switch. When turned On it powers the control logic. The amplifier enters the standby mode. To activate the amplifier you must press the POWER (STANDBY/OPERATE) Key on the front panel. Damping Factor switch On the rear panel in the center the damping factor (DF) switch is situated. This switch is normally positioned “down”. In this position the output amplifier output is 0.56 Ohm or DF = 15. If the switch is “up” the output impedance is 0.16 Ohm or DF = 50. Changing the DF will change the sound. The change depends on the speaker model, but a lot of speakers will sound more open and detailed with lower DF (i.e. DF = 15). NOTE: SWITCHING THE DAMPING FACTOR SELECTOR WHILE THE AMPLIFIER IS OPERATIONAL MAY CAUSE SOME NOISES TO BE HEARD IN YOUR SPEAKERS. © by www.audioalto.com 11 CLEANING The beautiful stainless steel (non-magnetic) and aluminum finish of the chassis and transformer top covers will last for years. A regular dusting with a soft, non-abrasive cloth will generally keep the finish looking like new. Fingerprints may be removed with a small amount of degreasing solution on a soft cleaning cloth. Be sure to apply any liquid into a soft cleaning cloth, not directly onto the chassis. At no time should you allow any liquids to drop onto the amplifiers; it may run into the electronic circuitry underneath and cause damage which will not be covered under your warranty! NOTE: Cleaning must be done with the amplifier turned off! TROUBLE-SHOOTING GUIDE If at any time the AA DMI 3 H amplifier fails to work, follow this simple checklist: 1) Make certain that the A.C. power cord is plugged in firmly, both at the A.C. wall socket and at the A.C. amplifier socket. 2) Remove the A.C. power cord at the amplifier and open the fuse hatch on the A.C. input socket. Check that: A. A “slow-blow” fuse, with a rating of 2 Amp 250V (0.25” x 1.25”), is installed for 120V AC or 1A Amp 250V (5mm x 20mm) for European and Asian versions. B. That the A.C. power fuse is intact and has not blown. If the power line fuse has blown, replace it with a same size and type fuse of the same rating (2 Amp 250V. slow-blows - 100 to 120 Volt Countries / 1 Amp 250V. - 200 to 240 Volt Countries). 3) If the fuse blows again without the power tubes installed, then you should return the amplifier to your dealer or to a service depot for repair. NOTE: Under no circumstances should you replace the A.C. power fuse with one of a higher current rating! Doing so may cause further damage to the amplifier in the event of a fault condition and will also void your warranty! In addition, your continued protection from the risk of fire or shock would be seriously compromised. NOTE: The surge capabilities of slow-blow fuses from different manufacturers vary. © by www.audioalto.com 12 WARRANTY AA DMI H3 comes with a transferable 3-year warranty. Tubes have a 6-month warranty. PRODUCT SPECIFICATION Phono Inputs – RIAA (optional): Moving Magnet Head - RCA 47Kohm, 47pF, 2mV sensitivity, overload margin 32dB, noise -70dB Inputs: I2 – RCA 220Kohm, 500 mVeff sensitivity (line input), Noise -95dB I3 – RCA 220Kohm, 200 mVeff sensitivity (line input), Noise -95dB Tape in – RCA 220Kohm, 200 mVeff sensitivity (line input), Noise -95dB Output: Tape out – RCA, 200 mVeff Headphone – 0.9 Veff @ 32 Ohms 7,5 Veff @ 600 Ohms 4 x Speakers posts 4 mm Vacuum tubes: 2 x 6922 (E88CC or NOS 6DJ8) Output Power: Model A: 2 x 30W @ 8 Ohm 2 x 50W @ 4 Ohm Model B: 2 x 60W @ 8 Ohm 2 x 100W @ 4 Ohm Output impedance @ 1 kHz (switchable): 0.56 Ohm – DF = 15 0.16 Ohm – DF = 50 Frequency response: 5Hz to 60.000Hz -1dB Dimensions: (W x D x H) 295 x 465 x 90 mm Weight: 12.5 Kg Finish: The AA DMI 3 H can be ordered in “Black”, “Chrome”, natural solid wood (i.e. walnut) or upon special order in various colors. © by www.audioalto.com 13