Friday, April 4, 2014

Accuphase A-70 amplifier

Exciting news coming from the headquarters of Accuphase Laboratory, Inc. in Yokohama, Japan! They are pleased to announce the new release of the incredible Class A A-70 amplifier (which replaces the A-65.) One of the higher-ups @ Accuphase was so kind to send us an exclusive pdf file on the A-70. Needless to say, that on paper, this looks to be Accuphase's best stereo amplifier to date! And a strong contender for the world's best!

For your copy of the pdf file, email us at: or

Edit: There is also a different standard pdf file now on the Accuphase website!

The A-70 will launch in the middle of this month in Japan. Other territories soon to follow.

For your convenience, here is the written part of the pdf without photos:

A-70 is a succession model of A-65 and the flag ship
class-A stereo power amplifier of Accuphase.
We already developed the flag ship class-A monophonic
power amplifier A-200 as 40 years anniversary model.
Technologies of A-200 were diverted to A-70.
In short, A-70 is stereo version of A-200.

The size of A-70 is as same as the former model A-65.
However A-70 is 1.3kg heavier than A-65 as chassis
structure is reinforced.

A-70 has digital power meters and 32-point LED bar
graph indications.
Digital power meter shows true output power without any
effect of speaker impedance.

2 pairs per channel of large speaker terminals are
They are useful for bi-wired connection with loud

Strong power supply by large Troidal transformer with
aluminum heat-radiation fins and 2 pieces of 82,000μF
capacitor are installed.

The chassis structure of A-70 was reinforced by 20mm x
15mm aluminum square bar on the front and back.
The continuous average output power is 60W into 8 ohm

However A-70 has bigger headroom for maximum output
power. It is 131W into 8 ohm and 547W into 1 ohm.
A-70 is the super high power amplifier.

A-70 has the lowest noise performance in the 41 years’
history of Accuphase stereo power amplifier.
Our first stereo power amplifier P-300 launched in 1973
has 40μV of noise voltage.
41 years later, A-70 achieves 13μV at last.
This is the half of the former model A-65.

The output noise is reduced by some technologies.
Optimizing gain allocation of 2 amplifier blocks
constructed with instrumentation amplifier.
Enhancing gain of balanced input amplifier block from 4
times to 12.6 times.
Output noise voltage is ideally decreased to 33%.

The output noise is also reduced by the discrete
configuration amplifier which IC is not installed on signal

A-70 has the highest Damping-Factor specification in the
41 years’ history of Accuphase stereo power amplifier.
DF of P-300 in 1973 was 60.

After 41 years, A-70 achieves 800 of DF.
This is 2 times higher than the former model A-65.
This is guaranteed specification. In actuality A-70 has
1,000 of DF.

*Damping-Factor, DF:
A index of speaker driving ability. Higher Damping-Factor
amplifier has higher speaker driving ability.
DF = 8 ohm / Output-impedance

The Output impedance is decreased by 10 parallel pushpull
output stage arrangement of MOS-FET.
Remote-sensing is the technique to lower output
impedance of amplifier by the negative feedback with
signal sensing from close up the speaker terminals.
Balanced Remote-sensing is the technique to make
impedance even lower by GND sensing and the negative
feedback of GND level with adding the signal sensing.
Not only Damping-factor is improved but also Total
Harmonic Distortion and Intermodulation Distortion get
better by Balanced Remote-sensing.

Mechanical relay is the most common for speaker
protection. It does not have good reliability and so lower
contact resistance either.

A-70 employed MOS-FET switch instead of mechanical
relay for speaker protection.
Damping-Factor, reliability and sound quality are
improved thanks to MOS-FET switch.

Some other very low impedance/resistance components
which are chosen for A-70 are large speaker terminal,
rectangular wire coil and so on.
Making signal path thick and short attains having low

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