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