A-70 is a succession model of A-65 and the flag shipclass-A stereo power amplifier of Accuphase.
We’ve already launched 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.

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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.

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The chassis structure of A-70 was reinforced by 20mm x15mm aluminum square bar on the front and back.

3A-70 has digital power meters and 32-point LED bargraph indications.
Digital power meter shows true output power without any
effect of speaker impedance.
2 pairs per channel of large speaker terminals areequipped.
They are useful for bi-wired connection with loudspeakers.

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

5The continuous average output power is 60W into 8 ohmload.
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.

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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.

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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 4times to 12.6 times.
Output noise voltage is ideally decreased to 33%.

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The output noise is also reduced by the discreteconfiguration amplifier which IC is not installed on signal
path.

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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

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The Output impedance is decreased by 10 parallel pushpull output stage arrangement of MOS-FET.

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Remote-sensing is the technique to lower output
impedance of amplifier by the negative feedback withsignal 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 getbetter by Balanced Remote-sensing.

12Mechanical relay is the most common for speakerprotection. It does not have good reliability and so lower
contact resistance either.
A-70 employed MOS-FET switch instead of mechanicalrelay for speaker protection.
Damping-Factor, reliability and sound quality are
improved thanks to MOS-FET switch.
Some other very low resistance components which arechosen for A-70 are large speaker terminal, rectangularwire coil and so on.
Making signal path thick and short attains having low
impedance.

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