m Pure Class A operation delivers quality power: 60 watts × 2 into 8 ohms
m Power MOS-FET output stage features 10-parallel push-pull configurationm Input circuitry with MCS topology m Current feedback design combines
superb sound with total operation stability m Bridged mode allows use as amonaural amplifier m Massive “Super Ring” toroidal transformer rated for 1 kVA
m Dual-function power meters show digital readout or bar graph display

Aiming for the ne plus ultra Experience the peerless sound of pure class Aand MOS-FETs. Input stage with MCS topology assures impeccableperformance in all aspects with minimum noise and distortion. 10-parallel pushpull power MOS-FETs operating in pure class A, and power supply withmassive 1 kVA toroidal transformer deliver linear power into ultra-low
impedances down to 1 ohm. 4-step gain selector further reduces residual noise.

Note 1

Low amplifier output impedance

The load of a power amplifier, namely the loudspeaker generates
a counterelectromotive force that can flow back into the amplifier
via the NF loop. This phenomenon is influenced by fluctuations inspeaker impedance, and interferes with the drive performance of
the amplifier. The output impedance of a power amplifier should
therefore be made as low as possible by using output devices
with high current capability. This absorbs the counterelectromotive
force generated by the voice coil and prevents the occurrence ofintermodulation distortion.

Note 2The constant drive voltage principle

Even in the presence of a load with wildly fluctuating impedance,
the ideal power amplifier should deliver a constant voltage signal
to the load. Figure 2 shows the results of actual output voltage/
output current measurements at different load impedances for theA-60. It can be clearly seen that output voltage is almost constantat various loads, which means that current increases in a linear
fashion. Actual measurements of clipping power have yielded thefollowing figures, which impressively demonstrate the more thanample performance of the A-60: 1 ohm: 513 watts, 2 ohms:343 watts, 4 ohms: 202 watts, 8 ohms: 110 watts.

Power MOS-FET output stage with 10-parallel pushpull power units delivers 480 watts into 1 ohm, 240
watts into 2 ohms, 120 watts into 4 ohms, or 60
watts into 8 ohms with outstanding linearity* 1-ohm loads to be driven with music signals only

The output stage (Figure 1) uses power MOS-FETs.
10 pairs of these devices are arranged in a parallel

Output current (A)The monophonic power amplifier M-8000 as
well as the stereo power amplifiers P-7000 andP-5000 from Accuphase are highly acclaimed
milestones in the history of high-class amplifiers.
Featuring similar design technology as thesemodels, the A-60 is a no-holds-barred pure classA stereo amplifier. Accuphase also has createda long and distinguished line of high-output
pure class A amplifiers. The musical qualities of
our A-100, A-50, and A-50V models have won
the admiration of audio connoisseurs the world
over. The A-60 is a worthy heir of this tradition.
In the input stage, the inventive MCS principle
pushes the noise floor down to amazingly lowlevels. Current feedback topology combines
operation stability with excellent frequency
response. Only minimal amounts of negative
feedback are needed, which is highly beneficialin terms of sound quality. At the same time, theA-60 is designed to realize two major goals:
very low output impedance (Note 1), andconstant drive voltage (Note 2).
The power MOS-FETs used in the output stage
are renowned for their superior sound and highreliability. Ten pairs of these devices arearranged in a parallel push-pull configurationfor each channel. These superb devices aredriven in a pure class A circuit configuration.
Reflecting Accuphase's vast expertise andunwavering dedication to sound quality, theA-60 brings out even the most delicate nuancesin the source with full authority.
Pure class A operation means that the circuit
always draws the same amount of power fromthe power supply, regardless of the presenceor absence of a music signal. It is impervious
against external influences and has highstability. The output stage producesconsiderable amounts of thermal energy, but
because the MOS-FET devices used in theA-60 have negative thermal characteristics,
there is no danger of thermal “runaway” as exists
with bipolar transistors. In addition, extra-large
heat sinks on both sides of the amplifier help toprevent internal heat buildup.
Another attractive feature of the A-60 is thesophisticated power meters with digital readout
and bar graph indication. A dedicated DSP
performs arithmetic operations that allow themeters to always show the true power levels of
the constantly changing music signal.

Output voltage (V)* 1-ohm operation possible
with music signals onlyFig. 2 Output power vs. load impedance(output voltage/output current)

where linearity is excellent.
A music signal consists of a continuous successionof pulse waveforms. To prevent clipping on occasional
momentary high-level pulses, the maximum clippinglevel of the A-60 is set to 100 watts per channel into
8 ohms.
MCS topology in input stage reduces residual noiseand drastically improves S/N ratio

Power MOS-FETs

The input stage which has an important role to playfeatures Accuphase's innovative MCS (Multiple Circuit

push-pull configuration for each channel. The result
is stable operation with ideal power linearity evendown to ultra-low impedances. The maximum power
dissipation of one MOS-FET is 130 watts, but theactual power load per pair is only 6 watts, so thateach device is driven only in its low-power range

BIASSTABILIZERSumming) design. Three separate unit amplifiers forthe input signal are connected in parallel, which
minimizes noise anddistortion and greatly
improves other performanceparameters as well. This
manifests itself in further
improved sound quality.
Gain control also switches
NFB for reduced noise floor

BIAS STABILIZER

The gain control of the A-60
has four positions: MAX,–3 dB, –6 dB, –12 dB.
Reducing the gain also results

CONSTANTCURRENTCIRCUITBIAS
STABILIZER

Fig. 1 Circuit diagram of amplifier section (one channel)Power amplifier assembly with 10parallel push-pull output devices
mounted to large heat sink, MCS
circuit, and current feedback
amplifier circuitry (one channel)

in correspondingly lower noise,
which can be very beneficial whendriving high-efficiency speakers
where residual noise can be a problem.
Current feedback circuit topology
assures excellent phase characteristics
in high range
In the A-60, the signal current rather than themore conventionally used voltage is used for feed-– Input
BufferCurrent
adder

I-V
converter

OutputAmplifierTrans-impedance
amplifier+ Input
BufferCurrent NFB
networkFig. 3 Principle of current feedback amplifierGain(Large)

back. Since the impedance at the current feedback point (current adder in Figure 3) is very low,
there is almost no phase shift. Phase compensation therefore can be kept at a minimum. A minimal
amount of NFB results in maximum improvement ofcircuit parameters. The result is excellent transient response
and superb
sonic transparency, coupledwith utterly
natural energybalance. Figure
4 shows freFrequency(High)
quencyre- Fig. 4 Frequency response with current feedback(Response remains uniform also when gain changes)
sponse for dif-ferent gain settings of the current feedback amplifier. The graphs demonstrate that response remains uniform over awide range.
Bridged operation mode creates true monophonicamplifier with 960 watts into 2 ohms, 480 watts
into 4 ohms or 240 watts into 8 ohms
* 2-ohm loads to be driven with music signals only

Bridged connection turns the A-60 into a monophonicamplifier with four times more power than during
stereo operation. The result is an extremely capable
performer with almost unlimited reserves.
Robust power supply with large "Super Ring"
toroidal transformer and 82,000 µF filtering
capacity
The power supply section is a critical aspect ofany power amplifier. The A-60 features a large
toroidal power transformer with a rating of about 1kVA. The transformer is housed in a non-resonant

aluminum enclosure filled with
damping material
that has excellent
heat transfer characteristics. Toroidal transformers
which use heavygauge copper wiring on a ringshaped core haveimportant advantages for audio applications, such asvery low impedance, small size,and high conversion efficiency.

Power meters switchable for digital readout and bar graph indication
The power meters of the A-60 have a dual function. They can show a digital
readout of true output power (5 digits), or operate as a bar graph indicator with
25 LED points. The meterselector has positions formeter OFF, different wattranges, and bar graphoperation.

Power meter block diagram

Voltagedetector

18-bitA/D converter

Current
detector

18-bitA/D converter

Meter OFF
Meter range
Bar graph switching

18-bitA/D converter

Currentdetector

18-bitA/D convertern Balanced connection eliminates induced noisen Input type selector button (balanced/unbalanced) on front paneln PCB copper foil and all major signal path components are goldplated
n Meter hold time can be switched to
1 second or infinite
n Selector allows switching to Dual Mono,Stereo, or Bridged operation
This indication is shown
for a few seconds afterpower-on when bridged
mode is selected

Hold timeselection

Left-channel
5-digit displayLeft-channel
bar graph

DSP
Absolute value
conversion

Voltagedetectorn Oversize speaker terminals compatible with Y lugs and bananaplugs

Microprocessor

Multiplication

Right-channel
5-digit display

Peak hold

Assembly with meter circuitry and protection circuitry

Right-channel
bar graph

Unbalanced and balanced input connectors

n Front panel

Gold-plated parts

Large speaker terminals

GUARANTEED SPECIFICATIONS[Guaranteed specifications are measured according to EIA standard RS-490.]m Continuous Average Output Power (20 - 20,000 Hz)
Stereo operation
480 watts per channel into 1 ohm (❇)(both channels driven)
240 watts per channel into 2 ohms
120 watts per channel into 4 ohms
060 watts per channel into 8 ohms
Monophonic operation
960 watts into 2 ohms (❇)(bridged connection)
480 watts into 4 ohms
240 watts into 8 ohms
Note: Load ratings marked (❇) apply only to operation with music signals.

n Rear panelm Total Harmonic Distortion

Stereo operation (both channels driven)
0.07%, with 2-ohm load
0.05%, with 4 to 16-ohm load
Monophonic operation (bridged connection)
0.03%, with 4 to 16 ohms loadm Intermodulation Distortion 0.003%
m 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

m Gain28.0 dB (GAIN selector: MAX, stereo/monophonic operation)

m Gain Switching

Max (28 dB), –3 dB (25 dB), –6 dB (22 dB), –12 dB (16 dB)

m Output Load Impedance

Stereo operation:
2 to 16 ohms
Monophonic operation: 4 to 16 ohms

❇ With music signals only, 1-ohm loads are permissible for stereo operation and 2-ohm
loads for monophonic operation.

m Damping Factor

100m Input Sensitivity(with 8 ohm load)

Stereo operation
Monophonic operation★
A Hold time indicator
B Left/right channel power meters(digital readout/bar graph switchable)
C Input type indicator
D Meter switch(OFF, range selection, bar graph)
E Hold time selector (1 second/ )F Power switch
G Input selector
H Gain selector(MAX, – 3 dB, – 6 dB, – 12 dB)★

I Left/right channel speaker output terminals
J Unbalanced inputs
K Balanced inputs
a Groundb Inverted (–)
c Non-inverted (+)
L Mode selector
DUAL MONO NORMALM AC circuit breaker★
N AC power connector★

Remarks★ This product is available in versions for 120/230 V AC. Make sure that the voltage
shown on the rear panel matches the AC line voltage in your area.
★ The shape of the AC inlet and plug of the supplied power cord, and the circuit
breaker current rating depend on the voltage rating and destination country.

n Supplied accessories:

m Input Impedance

40 kilohms (balanced), 20 kilohms (unbalanced)

m Signal-to-Noise Ratio(A-weighted)

112 dB at rated output, input shortedm Output Level Meters(digital and bar graph)

Digital meters:
5-digit indication, with range selection for 10W/100W/1000W
Bar graph meters: 25-point indication
Hold time:
1 second/ (switchable)✽ Display can be switched off.

BRIDGE

0.87 V for rated output (60 W)
0.11 V for 1 watt output
1.74 V for rated output (240 W)
0.11 V for 1 watt output✽ Same indication for left/right in monophonic modem Power Requirements

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

300 watts idle
550 watts in accordance with IEC-65

m Maximum dimensions

WidthHeightDepthm Mass

45.1 kg (99.4 lbs.) net
54.0 kg (119.0 lbs.) in shipping carton

465 mm (18-5/16”)
238 mm (9-3/8”)
545 mm (21-7/16”)• AC power cord

• Specifications and design subject to change without notice for improvements.

http://www.accuphase.com/

D0405Y PRINTED IN JAPAN 851-0137-00 (AD1)