m Ultra-powerful output stage with 22 parallel push-pull transistors
remains linear down to extremely low 1-ohm load impedance m MCS
configuration in input stage m Stabilized power supply in driver stagem Current feedback circuit topology assures great sound and stable
operation m Bridged use of two units possible for four times the output
power m Massive Super Ring toroidal transformer rated for 3 kVA max.

When developing the M-8000, Accuphase took a fresh
look at the entire concept of the power amplifier. As aresult, the M-8000 was designed to realize the idealof constant voltage drive, which is best implemented
in a monophonic configuration. In order to bring out
the full performance potential of any loudspeaker,
unaffected by the often drastic fluctuations in speaker
impedance, the amplifier must have very low output
impedance (Note 1), and it must be able to supply aconstant drive voltage (Note 2).

Note 1:
Low amplifier output impedance
When forming the load of a power amplifier a loudspeakergenerates a counterelectromotive force that can flow back into theamplifier via the NF loop. This phenomenon is influenced byfluctuations in speaker impedance, and interferes with the drive
performance of the output circuitry. The internal impedance of apower amplifier should therefore be made as low as possible byusing output devices with high current capability.

In the M-8000, a complement of 22 output transistors
with a collector dissipation (Pc) of 150 watts each isused in the output stage. Connected in parallel, thesedevices have a combined collector dissipation of 6,600watts. At the extremely low load impedance of 1 ohm,
the amplifier is rated to deliver an amazing 2,000 watts.
Constant voltage drive enables linear progression ofoutput vs. load impedance. This performance issustained by a massive Super Ring toroidaltransformer housed in a diecast enclosure with directly
mounted heat sinks, and by large filtering capacitors.
The transformer is rated for 1,5 kVA, max. 3,0 kVA,
and there are two capacitors of 40,000 µF each. Thisassures more than ample reserves and allows theM-8000 to meet even the most demanding and rapidly
fluctuating power requirements. Use of two units inbridged configuration is also possible, resulting in amono amplifier with even higher capabilities.

Note 2:
Constant drive voltage principle
Even when the impedance of a load fluctuates drastically, the ideal
power amplifier should deliver a constant voltage signal to the load.
When the supplied voltage remains constant for any impedance,
output power will be inversely proportional to the impedance ofthe load. A conventional amplifier can be easily made to operate
in this way down to a load impedance of about 4 ohms. However,at 2 ohms and below, much more substantial output reserves areneeded. This can only be achieved by a thorough redesign of allbasic amplifier aspects.

Ultra-powerful output stage with 22 parallel pushpull transistors delivers 2,000 watts into 1 ohm,
1,000 watts into 2 ohms, 500 watts into 4 ohms
and 250 watts into 8 ohms
The M-8000 uses a complement of 22 high-powertransistors with a collector dissipation (Pc) of 150
watts and a collector current of 15 amperes each.

The important input stage also has been given due
attention. Another Accuphase innovation called MCS(Multiple Circuit Summing) helps to minimize noise.
The predriver stage features a DC stabilized power
supply. This results in drastically improved S/N ratio,minimum distortion, and superb performance in allother aspects. Stable output is achieved regardlessof fluctuations on the AC side. Current feedback
topology makes it possible to combine stable
operation with impeccable frequency response. The
circuit boards of the M-8000 possess a Teflon basewith low dielectric constant and minimum loss.
Balanced inputs help to shut out external noise. The
copper foil side of PCBs and all input and output
terminals as well as all major signal carrying points
are gold plated. The overall result of these measures
is musical purity that leaves nothing to be desired.
* Teflon is a registered trademark of DuPont USA.

These devices are excellent in ever y regard,
including frequency response, current amplification
linearity, and switching characteristics. The 22
devices are connected in a parallel push-pull
configuration and mounted to immense heat sinks

Output current (A)A monophonic power amplifier with impressive muscle: 2000 watts into
1 ohm MCS topology for input stage assures high S/N ratio. 22 wide-band
high power transistors in parallel push-pull configuration. Power supply
with massive 3 kVA toroidal power transformer realizes constant voltage
speaker drive and delivers linear power down to impedances as low as one
ohm. Teflon PCBs with low dielectric constant and minimum loss.

Output voltage (V)* 1-ohm operation possible
with music signals only

Fig. 2 Output power vs. load impedance(output voltage/output current: actual measurements)

made of diecast aluminum. This assures efficientdissipation of thermal energy and provides plenty ofperformance margin. As a result, the power amplifieris capable of delivering enormous output power in a
linear progression towards lower load impedances:
2,000 watts into 1 ohm, 1,000 watts into 2 ohms,
500 watts into 4 ohms and 250 watts into 8 ohms.
The M-8000 also is able to drive reactive loads withease.
Figure 2 is a graph plotting the output voltage versus
current characteristics. Even when the load changes,
the output voltage remains almost constant, showinglinear current progression. Actual measurement ofclipping power at the extremely low load impedanceof 1 ohm yields 2,330 watts. At 2 ohms, the figure is
1,230 watts, at 4 ohms 630 watts, and at 8 ohms
310 watts. This demonstrates the impressive
performance reserves of this amplifier.
MCS topology in input stage drastically improves
S/N ratio
The input stage features Accuphase's original MCS(Multiple Circuit Summing) design. Three separate
unit amplifiers for the input signal areconnected in parallel, which
minimizes noise and distortion andgreatly improves other performanceparameters as well. This manifests
itself in fur ther improved soundquality.

Constant current
circuit

Bias stabilizer
circuitFig. 1
Circuit diagram of amplifier section

Stabilized power supply in driverstag e assures outstanding
operation stability
Bias stabilizer circuit

Bias stabilizer circuit

Bias stabilizer
circuit

The MCS circuitry and predriver stage
employ a DC stabilized power supply.
When the power stage amplifies asignal to large amplitudes, this could
cause noise in the input stage via thepower supply. This is prevented by
fixing the voltage of the predriverstage, to improve the quality of thepower supply for the low-level
amplification stages. Outstanding
S/N ratio and stable operation
unaffected by ambient temperatureand by AC line fluctuations isguaranteed at all times.

Current feedback circuit
topology prevents phase shifts
in high frequency range
The M-8000 employs the original
Accuphase current feedback principle.
Figure 3 shows the operating principleof this circuit. At the sensing point of thefeedback loop, the impedance is kept low andcurrent detection is performed. An impedance-– Input
Buffer+ Input
Buffern Power amplifier assemblywith MCS circuit, current
feedback amplifier circuitry,and output stage with 22parallel push-pull transistors
mounted directly to two large
aluminum diecast heat sinks

Current adder
I-V
converter

AmplifierOutputTrans-impedance
amplifierCurrent NFB
networkFig. 3 Current feedback amplifier principle diagram

converting amplifier then turns the current into avoltage to be used as the feedback signal. Since theimpedance at the current feedback point (currentadder in Figure 3) is very low, there is almost nophase shift. Phase compensation can be kept to aminimum,resulting in
excellent
transient
response andsuperb sonictransparency.
Figure 4 shows
frequency
Fig. 4 Frequency response with current feedback(Response remains uniform even when gain changes)
response fordifferent gain settings of the current feedback
amplifier. The graphs demonstrate that response
remains uniform over a wide range.
Use of two M-8000 in bridged configuration
possible, resulting in a mono amplifier with fourtimes the power
Bridged operation means that two amplifiers are
driven by the same signal voltage but with opposite
phase. The speaker load is then connected between
the positive output terminals of the amplifiers. Whenused in a bridged configuration, two M-8000 units forma single mono amplifier with awesome power
capabilities: 4,000 watts into 2 ohms, 2,000 watts into
4 ohms, or 1,000 watts into 8 ohms.

Printed circuit boards made from Teflon with low
dielectric constant and low loss
The printed circuit boards for the signal-carrying
circuits are made of Teflon, a glass fluorocarbon resinmaterial. Teflon has extremely low specific inductive
capacity which is desirable for fast signal transmission
and a low dielectric dissipation factor which results inminimal transmission losses. High-frequency
characteristics and heat resistance are also excellent.
For further improved sound quality, the copper foil side
is gold plated.

Robust power supply with "Super Ring" toroidal transformer and high filtering
capacity
The M-8000 features a massive toroidal power transformer with a maximum rating of
3 kVA. The transformer is housed in a non-resonant aluminum case filled with a material
that transmits heat and absorbs vibrations. This completely prevents any adverse
influences on other circuit parts. A toroidal transformer uses heavy-gauge copper
wiring on a doughnut-shaped core. This results in low impedance and high efficiency,
while
allowing
compact dimensions.
Twoultra-large
aluminum electrolytic
capacitors rated for
40,000 µF eachserve to smooth out
the pulsating direct
current from therectifier, providing
more than ample
filtering capacity.

n Balanced connection blocks induced noisen PCB copper foil and all major signal path components are gold-plated
n Phase selector
n Extra-large speaker terminals

Unbalanced and balanced inputs("2" indicates output connector for bridged connection)

Phase selector

Speaker terminals

Gold-plated circuit components

n Front panel

Parallel connection of output devices
Semiconductor devices for high-frequency applications often use the multichip principle where many small transistors or FETs are internally connectedin parallel. This reduces internal noise and the internal impedance of thedevice. It also results in a larger surface area of the chip, allowing the heatto disperse more easily. This in turn contributes to operation stability. The
M-8000 is based on a similar principle. By using multiple devices connectedin parallel, current load is distributed. Signal attacks and transients which
require a high amount of current to be available almost immediately can behandled with ease. But parallel connection in an Accuphase amplifier means
more than simply stringing together a number of devices. Various
sophisticated techniques are used to accommodate temperature
characteristics and to optimize the current flow pattern. As a result, distortion
at low current levels is improved, and signal-to-noise ratio is outstanding,assuring impressive dynamic range and sonic transparency. Ample current
capability makes it possible for the amplifier to drive even extremely low
loads with ease.

GUARANTEED SPECIFICATIONS

n Rear panel[Guaranteed specifications are measured according to EIA standard RS-490.]m Continuous Average Output Power (20 - 20,000 Hz)
2,000 watts into 1 ohm (0)1,000 watts into 2 ohms
500 watts into 4 ohms
250 watts into 8 ohms
Note: The rating marked (0) is for music signals only.
m Total Harmonic Distortion

0.05% with 2-ohm load
0.03% with 4 to 16-ohm loadm Intermodulation Distortion 0.003%0A Peak Power Meter(Output indication in dB and %)B Meter Display ON/OFF Switch
C Power Switch
D Speaker Terminals
E Unbalanced Input Jacks
F Input Selector
UNBALANCEDBALANCED

At rated continuous average output: 20 - 20,000 Hz +0 –0.2 dB
At 1 watt output:
0.5 - 160,000 Hz +0 –3.0 dB

m Gain:28.0 dB

m Output Load impedance:Continuous output:
Music signal output:m Damping Factor:

400m Input Sensitivity

1.78 V for rated continuous average output
0.11 V for 1 watt output

m Input Impedance

Balanced:
Unbalanced:

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

125 dB with input shorted,
at rated continuous average output

0G Phase Selector
INVERTEDNON-INVERTED
H Balanced Input Connectors
a Groundb Inverted (–)
c Non-inverted (+)
I AC Circuit Breaker 0
J AC Inlet 0Remarks
0 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.
0 The shape of the AC inlet and plug of the supplied power cord, and the circuit breakercurrent rating depend on the voltage rating and destination country.

n Supplied accessories:m Frequency Response

2 to 16 ohms
1 to 16 ohms

40 kilohms
20 kilohms

m Analog Output Level Meter Logarithmic compression scale
Output indication in dB and %m Power requirements

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

170 watts idle
853 watts in accordance with IEC-65m Maximum dimensions

465 mm
258 mm
545 mm(18-5/16") width(10-3/16") height(21-7/16") depthm Weight

49 kg
58 kg

(108.0 lbs.) net(127.8 lbs.) in shipping carton• AC power cord

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

http://www.accuphase.com/H0205Y

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