Accuphase A-36 User Manual

● Pure Class A operation delivers quality power: 30 watts x 2 into 8 ohms ● Power MOS-

FET output stage features 3-parallel push-pull configuration ● Instrumentation amplifier principle
used in input stage ● Amplification stage implements further evolved MCS+ topology ● Current
feedback principle combines stable operation with outstanding sound quality ● Bridged
connection mode allows upgrading to monophonic amplifier ● Strong power supply with
massive high-efficiency transformer and large filtering capacitors ● 4-stage gain control

Redefining Essential Excellence Impressive Baseline Pure Class A Stereo
Power Amplifier. Input stage features fully balanced signal paths realized with ultra
low noise instrumentation amplifier topology. MCS+ design and current feedback
in amplification circuitry deliver outstanding S/N ratio and other performance
parameters for improved sound quality. Robust power supply and power
MOS-FET devices in triple-parallel push-pull configuration sustain power output of
150 watts per channel (music signals) down to impedances as low as 1 ohm. Output
stage with further lowered impedance realizes a damping factor of 400.

Pure Class A amplifiers from Accuphase have a long
and distinguished tradition and have attained widely
acclaimed levels of performance combined with
reliability and impeccable sound quality. Audiophiles
the world over continue to hold them in high esteem.
The Pure Class A Monophonic Power Amplifier
A-200 introduced on the occasion of the company's
40th anniversary, and the high-end Pure Class A
Stereo Power Amplifier A-70 opened up new realms
of sonic excellence and have become legendary as
reference audio devices. The new A-36 inherits
many of the outstanding design technology features
developed for the higher-end models. It redefines the
baseline for pure class A power amplifiers and repre­sents the same unwavering attention to detail and
dedication to sound quality for which Accuphase is
justly famous.

Latest instrumentation amplifier topology allows the
realization of fully balanced signal paths, while the
MCS+ circuitry combined with current feedback
topology and carefully selected high-grade materials
assure further enhanced performance and sound
quality. In the output stage, power MOS-FETs
renowned for their excellent frequency response,
sonic performance, and superior reliability are used
in a triple parallel configuration and driven in pure
class A. This is sustained by the strong power supply
featuring a massive transformer and two large

47,000 μF filtering capacitors. Output power in each

channel is rated for an impressive 150 watts into
1 ohm, 120 watts into 2 ohms, 60 watts into 4 ohms,
and 30 watts into 8 ohms. Even speakers with ultra­low impedance or drastic fluctuations in impedance
curve can be driven reliably by this impressive ampli­fier. In the output circuitry, MOS-FET switches are
used in place of relays, to eliminate mechanical
contacts and improve long-term reliability. Top-grade
materials, sophisticated circuit pattern technology,
and various other measures result in low impedance
and allow the realization of a damping factor of 400,
which represents a two-fold improvement over the
A-35. The well-proven analog power meters are
equipped with a sensitivity selector for easy observa­tion of low power levels, and a peak hold function
has been newly added.

■3-parallel push-pull arrangement of power

MOS-FETs delivers 150 watts (music signal)
into 1 ohm, 120 watts into 2 ohms, 60 watts
into 4 ohms, or 30 watts into 8 ohms.

■ Strong power supply with large high-efficiency

transformer and two 47,000 μF filtering capaci­tors.

■ Instrumentation amplifier principle for power

amplifier input stage allows fully balanced
signal transmission. MCS+ topology further improves S/N ratio.

■ Bridging allows upgrade to monophonic amplifier with even

higher power, delivering 300 watts into 2 ohms (music signal),
240 watts into 4 ohms, or 120 watts into 8 ohms.

■ Operation mode switch supports dual mono operation and

allows bi-amping connection.

■ Damping factor doubled to 400 contributes to enhanced

sonic definition.

■ Analog power meters.
Meter operation/light on/off switch, peak hold/normal

operation selector, sensitivity selector (0 dB, -20 dB).

■ 4-stage gain selector (MAX, -3 dB, -6 dB, -12 dB)

also minimizes residual noise.

■Semiconductor (MOS-FET) switches used for

protection circuitry.

Meter controls

Prevent contact problems and ensure long-term reliability.

Eliminating mechanical contacts from
signal path also further enhances sound
quality.

■ Balanced input phase selector switch.
If balanced input of preamplifier uses

pin 2 positive configuration, this switch
can be used for proper matching.

Speaker selector buttons

MOS-FET switches Phase selector

■ Two sets of large speaker terminals (A / B) also accept Y lugs.

Large speaker terminals

Protection and meter circuit assembly

Filtering capacitorsPower transformer

Input selector button

Line and balanced input connectors

Operation mode selector

Gain control selector

+

INPUT

INPUT

GAIN CONTROL

CIRCUIT

Signal input stage

＋

−

FEEDBACK
NETWORK

FEEDBACK
NETWORK

−

＋

MCS+ (Multiple Circuit Summing)

BIAS

STABILIZER

CIRCUIT

Q

1

Q

3

Q

2

Q

4

Q

5

Q

7

BIAS

STABILIZER

CIRCUIT

BIAS

STABILIZER

CIRCUIT

Q

6

Q

8

BIAS

STABILIZER

CIRCUIT

Q

9

Q11Q

Q10Q

Q12Q

Fig. 1 Circuit diagram of amplifier section (one channel)

Power amplification stage

Q

13

15

14

16

REGULATOR

Q

17

BIAS

STABILIZER

CIRCUIT

Q

18

REGULATOR

NFB

NETWORK

NFB

NETWORK

Q

19

Q

20

+B1

Q21Q23Q

Q22Q

24

B1

200W

Output power

characteristics

+B2

25

OUTPUT

SPEAKER
TERMINAL

Q

26

B2

200

180

160

140

120

100

Output power (W)

80

60

40

20

Max. output powerMax. output power

Rated output power

Rated output power

Power MOS-FETs

104W

104W

60W

60W

30W

30W

8Ω 4Ω 2Ω 1Ω

200W

159W

159W

150W

150W

120W

120W

60W60W

Impedance (Ohms)

Parts selected for high sound quality and reliability

Instrumentation amplifier configuration and further refined MCS+ topology

Amplification stage features instrumentation
amplifier topology for fully balanced signal paths

The instrumentation amplifier principle ensures
that all signal paths from the inputs to the
power amp stage are fully balanced. This not
only results in excellent CMRR (Common Mode
Rejection Ratio) and minimal distortion, it also
makes the amplifier highly resistant against
external noise and other external influences.
The result is a drastic improvement in operation
stability and reliability.

Power amplifier stageSignal input stage

INPUT

GAIN CONTROL

CIRCUIT

+

–

FEEDBACK
NETWORK

FEEDBACK
NETWORK

–

+

+

OUTPUT

–

+

‒ INPUT

Instrumentation amplifier principle

Further refined MCS+ topology for even
lower noise

MCS+ is a further refined version of this approach.
By extending parallel operation to the class-A
drive stage of the current/voltage converter, the
noise floor has been lowered further.

Current feedback principle assures excellent
phase characteristics in high range

As shown in the illustration, the A-36 uses the output
signal current rather than voltage for feedback.
Since the impedance at the current feedback point
is very low, there is almost no phase shift. A minimal
amount of NFB therefore results in maximum
improvement of circuit parameters.

−INPUT

＋INPUT

TRANS-IMPEDANCE AMPLIFIER

BUFFER

BUFFER

/V

CONVERTER

CURRENT ADDER

CURRENT NFB

NETWORK

Principle of current feedback
amplifier

AMPLIFIER

OUTPUT

Power amplifier assembly

Power amplifier assembly with
3-parallel push-pull power
MOS-FET arrangement mounted
directly to large heat sink, also
comprising MCS+ circuitry and
current feedback amplifier.

Accuphase’s original MCS (Multiple Circuit
Summing) principle uses a number of identical
circuits connected in parallel to achieve
superior performance charac­teristics.

■ Using two A-36 units, upgrade to bridged operation or bi-amping is possible. ■ Use the LEFT (BALANCED or LINE) input connectors for both units.

Connection example for bridged setup

Left loudspeaker Right loudspeaker Left loudspeaker Right loudspeaker

When the operation mode selector is set
to bridged mode, the A-36 becomes a
monophonic amplifier with even higher
power output.

−

＊The ● speaker terminals of the A-36 are not used.

LOW

Connection example for bi-amping setup

In a bi-amped setup, the speaker units for
the LOW frequency range and HIGH
frequency range are driven by separate
amplifiers, for optimum sound quality.

＊The speakers must have a built-in crossover network

HIGH

and separate inputs for LOW and HIGH range.

LOW

HIGH

RIGHT＋

A-36 for left channel A-36 for right channel A-36 for left channel A-36 for right channel

BRIDGE LED on
front panel lit on
both A-36 units

LEFT＋

To left channel inputTo left channel input

L

R

Preamplifier Preamplifier

RIGHT＋

Operation mode
selector set to
BRIDGE on both
A-36 units

■ Front Panel

q Right/left-channel output power meters

(dB and percent indication, switchable)

e

Meter selector

OFF / NORMAL /
HOLD (

)

r

∞



-20 dB button t Speaker selector buttons

y Power switch

A: ON/OFF B: ON/OFF

wFunction indicator LEDs

-20 dB METER / SPEAKER A,B / LINE /
BALANCED / BRIDGE

u Input selector button

LINE / BALANCED

■ Rear Panel

o Line inputs

!2 Operation mode

selector

DUAL MONO /

NORMAL / BRIDGE

!0

Balanced inputs 

 ② Inverted ( – ) ③ Non-inverted (＋)

(Can be changed with phase selector
switch !3)

!3 Balanced input phase selector switch

!1 Right/left-channel speaker

output terminals
A / B, two sets

LEFT＋

i Gain selector

MAX / -3 dB /

-6 dB / -12 dB

!4 AC power supply

connector

★

＋−＋

−

To left channel inputTo left channel input

L

R

＋−＋

Operation mode
selector set to
DUAL MONO on
both A-36 units

−

A-36 GUARANTEED SPECIFICATIONS

[Guaranteed specifications measured according to EIA standard RS-490]

●Continuous Average Output Power (20–20,000 Hz)

Stereo operation 150 watts per channel into 1 ohm (＊)
(both channels driven) 120 watts per channel into 2 ohms
 60 watts per channel into 4 ohms
 30 watts per channel into 8 ohms
Monophonic operation 300 watts into 2 ohms (
(bridged connection) 240 watts into 4 ohms
120 watts into 8 ohms

●



Total Harmonic Stereo operation (both channels driven)
Distortion 0.05% with 2 ohm load

0.03% with 4 to 16 ohm load

0.05% with 4 to 16 ohm load



Intermodulation Distortion

●


Frequency Response At rated output: 20 – 20,000 Hz +0, -0.2 dB

●

At 1 watt output: 0.5 – 160,000 Hz +0, -3.0 dB



Gain 28.0 dB (with GAIN selector at MAX)

●

(Stereo and monophonic operation)



Gain Selection MAX, -3 dB, -6 dB, -12 dB

●


Output Load impedance

●

Stereo operation: 2 to 16 ohms
Monophonic operation: 4 to 16 ohms
With music signals only, 1-ohm loads are

●



Damping Factor 400

●



Input Sensitivity (with 8-ohm load, GAIN selector in MAX position)

Stereo operation: 0.62 V for rated continuous average output (30 W)

0.11 V for 1 watt output

Monophonic operation: 1.23 V for rated continuous average output (120 W)

0.11 V for 1 watt output

●



Input Impedance

●Signal-to-Noise Ratio (A-weighted, input shorted)

112 dB (GAIN selector at MAX)
120 dB (GAIN selector at -12 dB)
At rated continuous average output

●



Output Level Meters -40 dB to +3 dB (indication in dB and %)
Logarithmic scale
Operation selector: OFF / NORMAL / HOLD (
Meter sensitivity selector (-20 dB)
＊Monophonic operation: same value displayed for
left/right

●



Power Requirements AC 120 V/230 V, 50/60 Hz
(Voltage as indicated on rear panel)

●



Power Consumption 155 watts idle
270 watts in accordance with IEC 60065

●



Maximum Dimensions Width 465 mm (18.31")
Height 171 mm (6.73")
Depth 425 mm (16.73")

●



Mass 22.8 kg (50.27 lbs) net

29.0 kg (63.93 lbs) in shipping carton

Monophonic operation (bridged connection)

0.01%

permissible for stereo operation and 2-ohm loads
for monophonic operation.

Balanced: 40 kilohms Line: 20 kilohms

Note: Load ratings marked (＊) apply only to

operation with music signals.

＊)

∞

)

Remarks

This produc t is available in vers ions for 120/2 20/23 0 V AC. Make sure that the voltage shown on the rear panel matches the AC line voltag e in your area.

23 0 V version has an Eco M ode that switches power off af ter 120 minutes of inac tivity.

The shape of the AC inl et and plug of the supp lied power cor d depends on the vol tage rating and destinatio n country.

■

Supplied accessory:

●

AC power cord



●

The specifications and appearance of this product are subject to change without notice.

F1405Y PRINTED IN JAPAN 850-2187-00（B1）