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Impressive power amplifi er capable of delivering 1000 watts 2 into 1 ohm -
Amplification stages feature fully balanced signal paths as found in high-
quality instrumentation amplifi ers. Further refi ned MCS+ topology and cur-
rent feedback design result in even better S/N ratio, distortion, and other
performance parameters. Massive, high-efficiency 1.5 kVA toroidal trans-
former and 11-parallel push-pull arrangement of high-power transistors de-
liver enormous amounts of linear power into ultra-low loads down to one ohm.
The P-7100 is a successor to the highly regarded
P-7000, inheriting its general design policy and major
features while realizing further improvements in vari-
ous aspects. A major new highlight is the overall in-
strumentation ampli er con guration, which allows
fully balanced signal transmission in all stages of
the ampli er. In addition, the power ampli er section
employs MCS+, an improved version of the innova-
tive Multiple Circuit Summing principle developed by
Accuphase. In conjunction with the famous current
feedback topology, this provides further improved
performance characteristics. Only strictly selected
high-quality parts and materials are used throughout,
and the output of the ampli er is designed to achieve
very low impedance and constant drive voltage.
In the output stage, 11 pairs of high-power transistors
with a rated collector dissipation of 150 watts are ar-
ranged in a parallel push-pull con guration for each
channel. The devices are mounted to large heat sinks
on both sides of the main chassis for ef cient dissipa-
tion of thermal energy generated during operation.
As a result, the ampli er is capable of delivering
power in a linear progression down to an ultra-low
load impedance of one ohm. Even speakers with very
low impedances as well as speakers whose imped-
ance uctuates drastically can be driven with ease.
By using the P-7100 in bridged mode, it is possible
to create a monophonic ampli er with even higher
power. This performance is sustained by a mas-
sive Super Ring toroidal transformer housed in an
aluminum enclosure with excellent heat dissipation
characteristics. The transformer is rated for 1.5 kVA,
and is coupled with two large ltering capacitors rated
for 56,000 µF each. This allows the ampli er to meet
even the most demanding and rapidly uctuating
power requirements with ease.
The input stage features another Accuphase in-
novation called MCS+ (Multiple Circuit Summing)
which helps to minimize noise. The material used
for printed circuit boards has a decisive in uence not
only on electrical characteristics but also on the sonic
end result. The P-7100 employs Te on boards with
extremely low dielectric constant and low loss. The
copper foil side of PCBs and all input and output ter-
minals as well as all major signal carrying points are
gold plated. Balanced inputs help to shut out external
noise. The combination of outstanding circuit design
with top-quality materials and parts produces music
of unsurpassed purity that immediately captures and
enchants the listener. Hearing is believing.
n 11-parallel push-pull power unit delivers guaranteed linear
power output of 1000 watts into 1 ohm (music signals only),
500 watts into 2 ohms, 250 watts into 4 ohms and 125 watts
into 8 ohms
The output stage uses high-power transistors with a rated collector
dissipation of 150 watts and collector current of 15 amperes. These
devices boast excellent frequency response, current ampli cation
linearity, and switching characteristics.
n Printed circuit boards made from Tefl on with low
dielectric constant and low loss
* Te on is a registered trademark of DuPont USA.
n Robust power supply with Super Ring toroidal
transformer and high fi ltering capacity
The P-7100 features a massive toroidal power transformer
with a maximum rating of 1.5 kVA, and two large electrolytic
capacitors rated for 56,000 µF each, specially selected for
optimum sound quality.
n Bridged connection allows upgrading to a true monophonic ampli-
fi er with 2000 watts into 2 ohms (music signals only), 1000 watts
into 4 ohms, and 500 watts into 8 ohms
Bridged connection results in a monophonic ampli er with four times the power
output than during stereo operation. This gives effortless dynamic power.
n Balanced inputs prevent externally induced noise
n
4-step gain selector minimizes residual
noise (MAX, -3 dB, -6 dB, -12 dB)
n PCB copper foil and all major signal
path components are gold-plated
n Mode selector makes it easy to switch
between dual mono, stereo, or bridged
operation
n Large direct-reading analog power
meters with meter on/off button
n Input selector button (balanced/unbalanced) on front panel
n Oversize speaker terminals accept also Y lugs
Toroidal transformerHigh-power transistors
Filtering capacitors
Gain selector Unbalanced/balanced input connectors
Meter and input selector buttons
* 1-ohm operation possible with
music signals only Output voltage (V)
Figure 2 Load impedance vs. output pow e (output voltage/output current)
Figure 1 Circuit diagram of amplifi er section (one channel) Gold-plated parts
Output current (A)
Bias stabilizer
circuit Bias stabilizer
circuit
Bias stabilizer
circuit
Bias stabilizer
circuit Bias stabilizer
circuit
Large speaker terminalsHighly reliable parts selected for
sound qualityAssembly with meter and protection circuitry
MCS+(Multiple Circuit )
Summing
+ INPUT
- INPUT
NFB
NETWORK
NFB
NETWORK
GAIN CONTROL
CIRCUIT
REGULATOR
NFB
NETWORK
REGULATOR
OUTPUT
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Instrumentation amplier conguration
Signal input stage
Power amplier stage
+ INPUT
- INPUT
GAIN CONTROL
CIRCUIT
NFB
NETWORK
NFB
NETWORK
OUTPUT
Instrumentation amp confi guration allows
fully balanced signal paths
The amplifiation sections of the P-7100 feature the
newly adopted instrumentation amplifier principle
whereby all signal paths from the inputs to the power
amp stage are fully balanced.
This results in excellent CMRR (Common Mode
n Power ampli er assembly with 11 parallel push-pull transistor
pairs per channel mounted directly to large aluminum diecast
heat sinks, instrumentation ampli er and MCS+ circuitry, and
current feedback ampli er
Instrumentation Amplifi er Principle and Further Refi ned MCS+ Topology
Current feedback circuit topology assures
excellent phase characteristics in high range
In the P-7100, the signal current rather than the
more conventionally used voltage is used for feed-
back. Since the impedance at the current feedback
point is very low, there is almost no phase shift.
Phase compensation can therefore be kept at a
minimum. A slight amount of NFB results in maxi-
mum improvement of circuit parameters.
I/V
converter Ampli er
Current NFB
network Trans-impedance
ampli er Current
adder
(-) input buffer
(+) input buffer
Principle of current feedback amplifi er
Output
Rejection Ratio) and minimal distortion. Another
significant advantage is that external noise and
other external influences are virtually shut out. The
result is a drastic improvement in power amplifier
operation stability and reliability.
Further refi ned MCS+ topology for even
lower noise
Accuphases original MCS (Multiple Circuit Sum-
ming) principle uses a number of identical circuits
connected in parallel to achieve superior perfor-
mance characteristics. MCS+ is a further refined
version of this approach. Improvements in the bias
circuitry of the input-stage buffer amplifier result in
greater stability. This in turn makes it possible
to extend the parallel operation approach
to the class-A drive stage of
the current/voltage convert-
er, thereby further lowering
the noise floor.
r
