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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
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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
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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.
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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.
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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!
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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
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AA DMI 3 H with radio remote controller
© by www.audioalto.com
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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.
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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.
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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
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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.
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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
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