Class-A STEREO POWER AMPLIFIER

A-80

Accuphase Laboratory, Inc.

The A-80 is the successor to the A-75, launched in 2018,
and incorporates the technology of the flagship A-300
Class-A mono power amplifier to exceed the soundquality and electrical performance of the A-75.
Although the A-80 is class A, it can output linear power in
all impedances and can drive any speaker perfectly.
The near-zero noise performance, combined with theattractive timbre of Class-A, creates a new expression ofmusic.
It also offers complete protection against abnormalconditions, satisfying the high demands of audiophiles
and music fans over the long term.

1Dimensions and weight• Unit dimensions are almost same as the former model A-75
• Slightly heavier than A-75
465 mm
515 mm

240 mm
※A-75: 238 mm

44.6 kg ※A-75: 43.9 kg

Accuphase Laboratory, Inc.

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The A-80 unit dimensions are almost the same as theprevious model A-75.
However, it is slightly heavier than the A-75.

2

Evolution of front panel design• The power meters re-positioned• The handle, power switch, and sub-panel are larger

A-75A-80

Accuphase Laboratory, Inc.

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The front panel of the A-80 has a powerful design, withthe power meters re-positioned and the handles, powerswitch, and sub-panel enlarged.

3Internal View
power amplifier engine

Output amplifier module

power amplifier engine
High-efficiency large
toroidal transformer

120000uF custom
made capacitor

Accuphase Laboratory, Inc.

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It has an intense power supply, a massive special-madehigh-efficiency toroidal transformer, and two sizeable
120000μF special-made filtering capacitors in the unit'scenter.
The filtering capacitors have the largest capacity of any
Accuphase product.
※The filtering capacitor of A-300 and A-75 is 100000μF.

4Output power• Rated output power is increased by 8% from A-75
8Ω4Ω*2Ω*

A-75

60W

A-80

65W

A-75
A-80

120W
130W

A-75

240W

A-80

260W
Rated output power*Limited to music signals

Accuphase Laboratory, Inc.

5The A-80 improves the Class-A operation area by 8%
over the A-75 as 65W into 8Ω load.
Rated output power is doubled when the load impedance
becomes 1/2; it reaches 260W into a 2Ω load.

5Ultra low noise• Guaranteed output noise voltage 7% lower than the A-75
– Guaranteed SN-ratio: 123dB
A-75

17.4 μV

A-80

16.1 μV
Guaranteed output noise voltage

7% down

Accuphase Laboratory, Inc.

6The former model A-75 has excellent noise performance;
however, the A-80 achieves even 7% lower guaranteedoutput noise voltage than the former model.

6Technology for ultra-low noise• Fully discrete configuration Balanced input amplifier
Right channel

Left channel

Gain control

Amplifier for positive-phasesignalAmplifier for positive-phasesignal

Amplifier for negative-phasesignalAmplifier for negative-phasesignalBalanced input amplifier module

Accuphase Laboratory, Inc.

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The output noise is reduced by a balanced input amplifierof fully discrete construction, newly designed in the A300's circuit configuration.
The overall amplification of the A-80 is set by the gain
control of the balanced input amplifier.
By reducing the amplification level, the output noise canbe further reduced.

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Super high damping factor• Guaranteed damping factor is the same as A-300– Guaranteed damping factor: 1000A-80

1000

A-300

1000
Guranteed damping factor

Accuphase Laboratory, Inc.

8The A-80 has a guaranteed Damping Factor of 1000. It isthe same as the A-300.
The actual value is well more than 2000.
*Damping-Factor:
An index of speaker driving ability. A Higher DampingFactor amplifier has higher speaker driving ability.
DF = 8Ω / Output-impedance

8Technology for high damping factor• Very low output impedance power amplifier engine– MOS-FET 10-parallel push-pull final stage
10-parallel N-Channel MOS-FET final stageGold-plated glass cloth
fluorocarbon resin printcircuit board

MCS+ voltage
amplifier stage
10-parallel P-Channel MOS-FET final stage

Power amplifier engine

Accuphase Laboratory, Inc.

9The 10-parallel push-pull arrangement of MOS-FETs in
the power amplifier engine’s final stage reduces theoutput impedance, thereby increasing the damping factor.
The gold-plated glass cloth fluorocarbon resin print circuitboard helps to improve lower impedance and reliability.
The voltage amplification stage uses Accuphase’s
original circuit MCS+* to reduce noise.
*MCS+(Multiple Circuit Summing-up plus):
It is a technique for improving the noise performance ofanalog amplification circuitry by using circuit summing-up.

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Technology for high damping factor• Balanced Remote-sensing– Feedback from speaker terminal proximity– Signal-line and GND-line sensing
Signal sensing

Speaker terminal+ Signal- GND
GND sensing

Power Amplifier

Accuphase Laboratory, Inc.

10

Remote sensing is the technique to lower the amplifier's
output impedance by the negative feedback with thesignal sensing from nearby the speaker terminals.
Balanced remote sensing is also the technique to lower
the output impedance by both the signal sensing and theGND sensing, that is, the negative feedback of the GNDlevel.
Balanced remote sensing improves not only the Damping
Factor but also the Total Harmonic Distortion and theIntermodulation Distortion.

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Technology for high damping factor• Speaker protection equipped with the MOS-FET switch circuit• Short signal path configuration
MOS-FET switch
Large speaker terminal
Rectangular wire coilOn-resistance: 1.6mΩ

Gold-plated busbar
Output module

Accuphase Laboratory, Inc.

11A mechanical relay is a typical speaker protection
component, but its contact resistance is higher thanpeople think.
Therefore, Accuphase has chosen the MOS-FET switch
instead of conventional mechanical relays for speakerprotection.
Thanks to this MOS-FET switch, the damping factor,
reliability, and sound quality are all improved.
The A-80 adopts a new MOS-FET, with a very low onresistance of 1.6mΩ(the A-75 used 2.0mΩ on-resistance
MOS-FET).
The A-80 also employs carefully selected very lowimpedance components such as large speaker terminals,
rectangular wire coils, gold-plated busbar, etc.
Making signal paths thick and short helps to attain low
impedance as well.
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Pursuing further product safety and reliability• Hall element detects the excessive output current• Temperature sensors are installed on the heatsink

Temperature sensor

Output module

Hall element

Power amplifier engine

Accuphase Laboratory, Inc.

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The Hall element on the output module detects
overcurrent in the event of an output short circuit,minimizing any adverse effects on the music signal.
The A-80 adopts temperature sensors that detect theheatsink temperature; thanks to this, the unit accurately
ascertains the high-temperature alarm in the power
amplifier engine.
*When these protection circuits are activated, the unit
completely interrupts the speaker output and makes thepower meters flash to indicate the abnormal condition.

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