Accuphase A-36 User Manual

Page 1

● 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

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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

GAIN CONTROL

CIRCUIT

Signal input stage

＋

−

FEEDBACK NETWORK

−

＋

MCS+ (Multiple Circuit Summing)

BIAS

STABILIZER

CIRCUIT

BIAS

STABILIZER

CIRCUIT

BIAS

STABILIZER

CIRCUIT

BIAS

STABILIZER

CIRCUIT

Q11Q

Q10Q

Q12Q

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

Power amplification stage

REGULATOR

BIAS

STABILIZER

CIRCUIT

REGULATOR

NFB

NETWORK

NFB

NETWORK

+B1

Q21Q23Q

Q22Q

200W

Output power

characteristics

+B2

OUTPUT

SPEAKER TERMINAL

200

180

160

140

120

100

Output power (W)

Max. output powerMax. output power

Rated output power

Power MOS-FETs

104W

60W

30W

8Ω 4Ω 2Ω 1Ω

200W

159W

150W

120W

60W60W

Impedance (Ohms)

Parts selected for high sound quality and reliability

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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

–

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

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.

Page 4

■ 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

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)

Meter selector

OFF / NORMAL / HOLD (

)

∞



-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

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

＋−＋

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）