Audio Database


Accuphase A-20V
330,000 yen(March, 2000 release)


Pure Class-A stereo power amplifier which inherited a design philosophy and circuit technology, such as a constant-voltage drive of Accuphase, and reduction in impedance, and adopted Power MOS FET as the output element.

Operation to heat has adopted the power MOS FET of the negative characteristic as an output magnification stage.
Three pairs are carrying out the parallel push pull drive of this power MOS FET per channel, and the linear power which was stabilized even as for super-low impedance load is guaranteed.
There is a merit of being able to distribute the heat which the parallel connection can make low the peculiar Output load impedance which an element has, and internal noise, and is generated from an element. Furthermore, the small electric power domain which was excellent in the linearity of MOS FET could be used efficiently, and it has contributed to the engine performance and the improvement in sound quality.
Moreover, in order to save the music signal of the momentary pulse which sometimes appears from clipping, the maximum clipping level is set as 50W at 8 ohms.
The actual measurement of clipping power is the design which had 156W (it limits to a music signal) by 1 ohm of loads and for which it had 126W and as sufficient by 85W and 8ohm at 4 ohms margin as 50W by 2ohm.

The current feedback magnification circuit (current feedback type magnification circuit) which returns an output signal in the form of current is adopted.
A principle lowers the impedance of the input terminal by the side of a return first, and detects current. I-V (current-voltage) conversion of the current is carried out with a transformer impedance amplifier, and an output signal is made.
Since it is hard to generate phase rotation since the impedance of a return input portion is low, and there is also almost no necessity for phase compensation, many characteristics can be sharply improved by a little NFB, and a natural energy response is possible.

Gain control of the amount change system of NFB is possible by the current feedback magnification circuit which there is no disorder of the phase by NFB, and is proud of the outstanding stability.
since a noise ingredient will also fall simultaneously by this system if the gain of an amplifier is lowered -- the crown of a high efficiency speaker or a multi-amplifier system -- power is demonstrated to reduction of the remains noises for regions etc.

The large-sized transformer of the efficient large power capacity of about 400 VA is adopted as a power-source part. This transformer is excellent in heat conduction, is enclosed with a case using the high load material of the vibrationproofing effect, and is intercepting the influence on the exterior.
Moreover, two large scale and high-quality sound types 47,000-micro F are carried in the aluminum electrolytic capacitor for smooth. This capacitor is insulated applying the heat contraction sleeve of wall thickness, and it has structure which absorbs vibration.

By a changeover switch on the back, bridge connection is possible.
Bridge connection inputs a negative phase signal into two polar different amplifier, is a system which connects a speaker to the output end of both amplifier, and can upgrade it to monophonic amplifier with this system.
Moreover, by the dual mono-position of a changeover switch, a mono-output is used, the output for center Woofers is used, or a 片 channel signal is outputted from both the speaker terminal, and it can be used as an object for the by amplifier drive only for low-pass / high region.

The balance contact button which cannot receive visitor guidance noise easily is carried.

The analog type large-sized power meter which can carry out the Direct reading of the large power range by a logarithm compression formula is carried.
Moreover, the switch which turns on and off operation and lighting of meter is also equipped.

Copper is used for the parts which a signal passes, and also plate-ization with gold is performed on this.
Improvement in the thorough sound qualities, such as a printed board Copper-foil side, an input terminal, an output terminal, is aimed at.

It is begun to delete brass Naked material, it is formed into a golden plate, and the large-sized speaker terminal on which the mould cap of the insulated purpose was put is carried on it.

Internal Power
Assy Input Speaker
Power MOS FET Power Power-source

Rating of a mode
Form Stereo power amplifier
Rated continuation average output
(For 20Hz - 20kHz)
At the time of stereo specification (both channel simultaneous operation)
2ohm:80 W/ch
4ohm:40 W/ch
8ohm:20 W/ch
At the time of monophonic specification (bridge connection)
4ohm: 160W
8ohm: 80W
THD At the time of stereo specification (both channel simultaneous operation)
2ohms : 0.05%
4-16ohms : 0.02%
At the time of monophonic specification (bridge connection)
4-16ohms : 0.02%
IM distortion 0.003%
Frequency response At the time of a rated continuation average output: 20Hz - 20,000Hz, and +0 -0.2 dB
At the time of 1W output: 0.5Hz - 160,000Hz, and +0 -3.0 dB
Gain (profit) 28.0dB (at the time of GAIN switch MAX o'clock, a stereo / monophonic specification)
Load impedance At the time of stereo specification: 2-16ohms
At the time of monophonic specification: 4-16ohms
Dumping factor At the time of stereo specification: 120
At the time of monophonic specification: 60
Input sensitivity (8-ohm load) At the time of stereo specification
0.50V (at the time of a rated continuation average output)
0.11V (at the time of 1W output)
At the time of monophonic specification
1.00V (at the time of a rated continuation average output)
0.11V (at the time of 1W output)
Input impedance Balance: 40kohm
Unbalance: 20kohm
S/N (A compensation) 110dB (at the time of input short-circuit and a rated continuation average output)
Power meter level A logarithm compression type, with a display putting-out-lights function
NORMAL : -40dB-+3dB
-20dB : -60dB--17dB
Power source AC100V, 50Hz/60Hz
Power consumption At the time of no inputting: 160W
Electrical Appliance and Material Control Law: 250W
At the time of an 8ohm Output power: 180W
Dimensions Width 475x height 170x depth of 426mm
Weight 22.6kg