m Output stage with 3-parallel push-pull configuration for each channeldelivers high power and handles very low impedance loads m Instrumentation
amplifier principle used for signal paths m Further refined MCS+ circuit
topology m Current feedback circuit combines excellent sound quality with total
operation stability m Bridged connection mode allows upgrading to monophonicamplifier m Massive toroidal transformer rated for 950 VA m 4-step gain control

Stereo power amplifier capable of delivering 500 watts into 1 ohm (musicsignal) – Instrumentation amplifier principle allows fully balanced signal paths.
Further refined MCS+ and current feedback topology assure outstanding
S/N ratio, minimum distortion, and excellent performance in all other aspects,
resulting in superb sound quality. 3-parallel push-pull arrangement of highpower transistors in each channel, sustained by power supply with massive
950 VA toroidal transformer. 4-step gain control minimizes residual noise.
The P-4100 is a stereo power amplifier that takes
sophisticated sound to the next level. Whileinheriting design technology from highly renowned
Accuphase models such as the P-7100 and M-6000,
the new model features instrumentation amplifier
topology and a refined MCS+ circuit to lower thenoise floor even further. Only specially selected
top-grade materials and parts are used throughoutwith impressive results.
In order to bring out the full potential of theloudspeakers, an amplifier must be able to copewith drastically fluctuating speaker impedance
conditions. This can only be achieved by ensuring
constant drive voltage at all times. In other words,
the output impedance of the amplifier must be kept
very low. This also makes it possible to absorb
the counterelectromotive force generated by thevoice coil, thereby eliminating a major source ofintermodulation distortion.
The P-4100 achieves these design goals with ease.
The output stage for each channel uses three pairs ofhigh-power transistors with a Pc rating of 220 watts,
arranged in a parallel push-pull configuration. Thisensures low output impedance. Stable operationis achieved by mounting the devices to massive
heat sinks on both sides of the chassis, for efficientdissipation of thermal energy. As demonstrated by
the power rating of 500 watts into 1 ohm (with musicsignals), the P-4100 can easily drive speakers withvery low impedance, and speakers with uneven
impedance curves are handled with complete
authority. Using the P-4100 in bridged mode createsa mono amplifier with even more impressive power
capability. The power supply section which acts asenergy source for the amplifier employs a massive
950 VA toroidal transformer in combination with large
filtering capacitors, providing ample reserves evenwith drastically fluctuating loads.
The overall configuration of the P-4100 employs thelatest instrumentation amplifier principle, allowing
fully balanced signal paths throughout. In addition,
the power amplifier section features refined MCS+
topology in combination with current feedback,for further enhanced electrical performance
characteristics.

n Power modules with high-power transistors in 3-parallel push-pullarrangement deliver 500 watts per channel into 1 ohm (music signals only),
360 watts into 2 ohms, 180 watts into 4 ohms, or 90 watts into 8 ohms.

n Amply dimensioned power supply with high-efficiency toroidal transformer
and large filtering capacity.
The high-efficiency toroidal transformer is rated for approx. 950 VA, and the two
extra-large 47,000μF aluminum electrolytic capacitors were selected for best sonicperformance.

Toroidal power transformern Bridged mode allows upgrading to monophonic amplifier with 1,000 watts
into 2 ohms (music signals only), 720 watts into 4 ohms, or 360 watts into
8 ohms.
Bridged connection increases the output by a factor of 4, creating dramatic power
reserves in a monophonic configuration.
Filtering capacitors

n Four gain control settings minimize residual noise.
The gain control alters gain in the first stage of the instrumentation amplifier. Four
settings are available (MAX, –3 dB, – 6 dB, –12 dB).

n Large analog power meters with on/off switch.
n Mode selector for easy switching between dualmono/stereo/bridged operation.

Meter on/off button Input selector

n Fully balanced input stage

Gain selector

shuts out external noiseinterference.

n Two pairs of oversize speakerterminals accept also Y lugs
plugs.
High-power transistors used in output stage

Large speaker terminals

Parts selected for sound quality and reliability

Assembly with meter and protection circuitry
Assembly with unbalanced and balanced input connectors

Instrumentation amplifier
Bias stabilizer circuit* 1-ohm operation possible with music signals only
REGULATOR+ INPUT

Bias stabilizercircuit
NFB
NETWORKGAIN CONTROLCIRCUITNFBNETWORK

Bias stabilizercircuit

OUTPUT

Bias stabilizer circuit

Output current (A)NFB
NETWORK– INPUTREGULATOR

Bias stabilizer circuit

Gain control

MCS+ (Multiple Circuit Summing)

High-power transistorsin 3-parallel push-pull configuration

Figure 1 Circuit diagram of amplifier section (one channel)

Output voltage (V)Figure 2 Load impedance vs. output power(output voltage/output current)Instrumentation amplifier and further refined MCS+ topology
Instrumentation amp configuration allows
fully balanced signal paths

Further refined MCS+ topology for evenlower noise

Current feedback principle assures excellent phase characteristics in high range

The newly adopted “instrumentation amplifier”
principle ensures that all signal paths from theinputs to the power amp stage are fully balanced.
This results in excellent CMRR (common mode
rejection ratio) and minimal distortion. Anothersignificant advantage is that external noise andother external influences are virtually shut out.
The result is a drastic improvement in operationstability and reliability.

Accuphase’s original MCS (Multiple CircuitSumming) principle uses a number of identicalcircuits connected in parallel to achieve superior
performance characteristics. MCS+ is a further
refined version of this approach. By extending
parallel operation to the class-A drive stage ofthe current/voltage converter, the noise floor
has been lowered further.

As shown in the illustration, the P-4100 uses
the output signal current rather than voltage forfeedback. Since the impedance at the current
feedback point is very low, there is almost nophase shift. A minimal amount of NFB therefore
results in maximum improvement of circuit
parameters.

+ INPUT
Signal input stage

Current adder

BufferPower amplifier stage

I/V converter

AmplifierTrans-impedance amplifier+ INPUT– INPUT
BufferCurrent NFB
network

NFB
NETWORKGAIN CONTROLCIRCUITOUTPUTNFBNETWORK– INPUT

Instrumentation amplifier configurationn Power amplifier assembly with three parallel push-pullhigh-power transistor pairs per channel mounted directly
to large heat sink, MCS+ circuitry, and current feedback
amplifier.

Principle of current feedback amplifierOutput

■ You can use two P-4100 units in bridged mode or in a bi-amping setup, for even higher quality.

■ Use the LEFT (BALANCED or UNBALANCED) input connectors for both units.

Bridged connection example
Left loudspeaker

Bi-amping connection example

Right loudspeaker

Left loudspeakerIn bridged mode, the P-4100 becomes amonophonic amplifier with even higher power
output.

Right loudspeaker

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 andseparate inputs for LOW and HIGH range.
Two P-4100 units are required.

For stereo operation, two P-4100 units arerequired.

P-4100for leftchannelP-4100for right
channelPreamplifier

P-4100for right
channelP-4100for leftchannelSet Mode
selector on bothP-4100 units toBRIDGE.

Set Mode
selector on bothP-4100 units to
DUAL MONO.

Preamplifiern Front Panel

GUARANTEED SPECIFICATIONS✽ Guaranteed specifications are measured according to EIA standard RS-490.
m Continuous Average Output Power (20–20,000 Hz)
Stereo operation
500 watts per channel into 1 ohm ( )(both channels driven)
360 watts per channel into 2 ohms
180 watts per channel into 4 ohms
90 watts per channel into 8 ohms
Monophonic operation(bridged connection)

1,000 watts into 2 ohms ( )720 watts into 4 ohms
360 watts into 8 ohms

Note: Load ratings marked ( ) apply only to operation with music signals.
m Total Harmonic Distortion

Stereo operation (both channels driven)
0.05% with 2 ohm load
0.02% with 4 to 16 ohm load
Monophonic operation (bridged connection)
0.02% with 4 to 16 ohm loadn Rear Panelm Intermodulation Distortion

0.01%

m Frequency Response

At rated output:
At 1 watt output:

m Gain28.0 dB (with GAIN selector at MAX)(in stereo and monophonic operation)

m Gain Selection

MAX, –3 dB, –6 dB, –12 dB

m Output Load impedance

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

20 - 20,000 Hz +0,0.5 - 160,000 Hz +0,–0.2 dB–3.0 dB

With music signals only, 1-ohm loads are permissible forstereo operation and 2-ohm loads for monophonic operation.
m Damping Factor

180

m Input Sensitivity (with 8-ohm load, GAIN selector in MAX position)
Stereo operation:
1.07 V for rated output
0.11 V for 1 watt output
Monophonic operation: 2.14 V for rated output
0.11 V for 1 watt output
m Input Impedance

Balanced: 40 kilohms

Unbalanced: 20 kilohms

m Signal-to-Noise Ratio (A-weighted, input shorted)
120 dB (GAIN selector at MAX)
125 dB (GAIN selector at –12 dB)
At rated output

A Right/left-channel output power meters (dBand % scale)
B Function indicators
UNBALANCED BALANCED BRIDGEC Speaker selector A B
A+B
D Meter on/off button ON
OFF
E Power switch
F Input selector button
UNBALANCED BALANCED
G Gain selector
MAX –3 dB –6 dB –12 dB

H Unbalanced inputs
I Right/left-channel speaker output terminals
A and B (two pairs)
J Mode selector
DUAL MONONORMAL
BRIDGEK Balanced inputs
a Ground b Inverted (–)
c Non-inverted (+)
L AC power supply connectorm Output Level Meters–50 dB to +3 dB (indication in dB and %)Logarithmic scale, with defeat switch

m Power Requirements

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

60 watts idle
550 watts in accordance with IEC 60065

m Maximum Dimensions

Width 465 mm (18-5/16")
Height 190 mm (7-1/2")
Depth 427 mm (16-13/16")

m Mass28.2 kg (62.2 lbs) net
34.0 kg (75.0 lbs) in shipping carton

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 depends on the voltage rating and destination country.

Supplied accessory● AC power cord

mSpecifications and design subject to change without notice for improvements.

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