m Triple parallel push-pull output stage in each channel delivers
plenty of linear power even into very low load impedancesm Instrumentation amplifier derived signal path designm Advanced MCS+ circuit topology m Bridged connection mode
allows upgrading to true monophonic amplifier m Massive Super
Ring toroidal transformer rated for 700 VA m 4-step gain control

A stereo power amplifier capable of delivering 400 watts into 1 ohm (with musicsignals) Fully balanced signal paths as found in high-quality instrumentation
amplifiers. Further refined MCS+ topology and current feedback
design. Improved S/N ratio, minimal distortion, and great
performance in all other areas. Power supply with massive
700 VA toroidal transformer and triple parallel push-pullarrangement of high-power transistors in each channel.
The P-3000 is based on the same design
technology as the renowned P-7000 andP-5000 models. Using only carefully selected top
quality parts throughout, the P-3000 is an ideal
match for the C-2000 preamplifier.

Note 1

Low amplifier output impedance

When forming the load of a power amplifier, a loudspeaker generates
a counterelectromotive force that can flow back into the amplifier via
the NF loop. This phenomenon is influenced by fluctuations in speaker
impedance and interferes with the drive performance of the amplifier.
The output impedance of a power amplifier should therefore be madeas low as possible by using output devices with high current capability.
This absorbs the counterelectromotive force generated by the voicecoil and prevents the occurrence of intermodulation distortion.

Note 21Ω

Output current (A)A new feature in the P-3000 is the fact that all
signal paths from the input terminals onwards are
fully balanced, an approach otherwise found only
in instrumentation amplifiers of the highest quality.
In addition, the power amplifier section employs
an improved version of MCS called MCS+(Multiple Circuit Summing plus), as well as thefamous Accuphase current feedback topology.
S/N ratio, distor tion, and other electricalcharacteristics are further improved. And ofcourse, these refinements manifest themselvesin even better sound quality.

Constant drive voltage principle

Even when the impedance of a load fluctuates drastically, the idealpower amplifier should deliver a constant voltage signal to the load.
Figure 2 is a graph plotting the output voltage versus current
characteristics. Even when the load changes, the output voltage
remains almost constant, showing linear current progression. Actual
measurement of clipping power at the extremely low load impedanceof 1 ohm yields 400 watts. At 2 ohms, the figure is 330 watts, at 4ohms 220 watts, and at 8 ohms 133 watts. This demonstrates theimpressive performance reserves of this amplifier.

In order to drive any kind of speaker with precision
and authority, a power amplifier must provide
extremely low output impedance (Note 1) and be
capable of supplying a constant drive voltage at
all times (Note 2). To realize constant-voltage
capability over the entire frequency range, a
powerful output stage supported by a capable
power supply are necessary.
In the output stage of the P-3000, three pairs ofhigh-power transistors are arranged in a parallelpush-pull configuration for each channel. The
devices are mounted to large heat sinks on bothsides for efficient dissipation of thermal energy.
Rated output power into an ultra-low impedanceof 1 ohm is 400 watts per channel (music signals
only). Power remains linear also when impedancechanges, as exemplified by the rating of 300 watts
into 2 ohms, 150 watts into 4 ohms and 75 watts
into 8 ohms. Even speakers with very low
impedance or with drastic impedance fluctuations
can be driven effortlessly and accurately.

330W

10220W
4Ω
133W
8Ω

00

Further refined MCS+ topology+ INPUT

Accuphase's original MCS (Multiple Circuit Summing)
principle uses a number of identical circuits

Power amplifier stage+–NFB
NETWORK+–GAIN CONTROLCIRCUITOUTPUTNFBNETWORK– INPUT–+connected in parallel to achieve superior
performance characteristics. The MCS+ is a further
refined version of this approach. Improvements inInstrumentation amplifier configuration

Q5

Q9Q 13+ B1Q7Q 11Q 15+ B2Q 19Q 21

Q 23

NFB
NETWORKGAIN CONTROLCIRCUIT

Bias stabilizercircuit

OUTPUT

Q2
Q 10Q 14Q 18Q 20Q 22Q 24

Q 26– B2Q8Triple parallel push-pull powerunit delivers guaranteed linear
power output of 300 watts into
2 ohms, 150 watts into 4 ohms,
and 75 watts into 8 ohms

Bias stabilizer
circuitNFB
NETWORKQ4

the bias circuitry of the input-stage
buffer amplifier result in greater
stability. This in tur n makes it
possible to extend the parallel
operation approach to the class-A
drive stage of the current/voltage
converter, thereby further lowering
the noise floor.

Q 25

Bias stabilizer
circuit–+40

The P-3000 features a new "instrumentation
amplifier" principle whereby all signal paths from theinputs to the power amp stage are fully balanced.
This results in excellent CMRR (common moderejection ratio) and minimal distortion. Anothersignificant advantage is that external noise and otherexternal influences are virtually shut out. The result

Q 17– INPUT

32★1 ohm rating is for music signals only.

Bias stabilizer
circuitQ6

24

is a drastic improvement in operation stability andreliability.

REGULATORNFBNETWORK16

Fig. 2 Load impedance vs. output power(Output voltage/output current)

Q1Q3

8Output voltage (V)+ B3+–71W16Ω

MCS++ INPUT

2Ω

Power amplifier with instrumentation ampconfiguration

Signal input stage

By using the P-3000 in bridged mode, it ispossible to create a monophonic amplifier witheven higher power reserves. This performance issustained by a massive high-efficiency Super
Ring toroidal transformer and large filtering
capacitors.

Circuit( MultipleSumming )400W

20Q 12Q 16
REGULATOR– B1– B3
Bias stabilizer
circuitFig. 1 Circuit diagram of amplifier section (one channel)

The output stage uses high-powertransistors with a rated collector
dissipation of 130 watts. These
devices feature excellent frequency
response, current amplification
linearity,
andswitching
characteristics. The transistors arearranged in a triple parallel pushpull configuration and mounted ona massive heat sink. This assuresn Power amplifier assembly with
3 parallel push-pull transistor
pairs per channel mounted
directly to large heat sink,
MCS+ circuitr y, and current
feedback amplifier

The P-3000 employs the renowned current feedback
principle developed by Accuphase. At the sensing
point of the feedback loop, the impedance is keptlow and current detection is performed. An
impedance-converting amplifier then turns thecurrent into a voltage to be used as the feedback
signal. Since the impedance at the current feedback
point (current adder in Figure 3) is very low, there isalmost no phase shift. Phase compensation can be– Input
Buffer+ Input
BufferCurrentadderI-V
converter

OutputAmplifierTrans-impedance
amplifierCurrent NFB
networkFig. 3 Principle of current feedback amplifier(Large)

Current feedback circuit topology prevents phaseshifts in high frequency rangekept to a minimum, resulting
in excellent transient response
and superb sonic transparency.
M i n i m a lamounts of NFB
are used tom a x i m u meffect, providing
natural energy
response.
Frequency(High)
Figure 4 shows
Fig. 4 Frequency response with current feedback
frequency(Response remains uniform also when gain changes)
response fordifferent gain settings of the current feedback
amplifier. The graphs demonstrate that response
remains uniform over a wide range.
Gaineffective heat dissipation and reduces theimpedance of the output stage.

Robust power supply with "Super Ring" toroidaltransformer and high filtering capacity
The P-3000 features a massive toroidal powertransformer with a maximum rating of 700 VA. The
transformer is housed in a case filled with a material
that transmits heat and absorbs vibrations. This

completely prevents any
adverse influences on othercircuit parts. A toroidal transformer
uses heavy-gauge copper wiring on adoughnut-shaped
core, resulting in
low impedance andhigh efficiency whileallowing compact
dimensions, whichis especially usefulfor audio applications.
Two ultra-largea l u m i n u melectrolytic
capacitors rated for
47,000 µF eachserve to smooth out
the pulsating direct
current from therectifier, providing
more than ample
filtering capacity.

Instrumentation amp type gain control
minimizes residual noise
The gain control switches gain in the first
amplification stage after
signal input. Four settings
are available (MAX, –3 dB,–6 dB, –12 dB). With thisapproach, reducing gain
also results in reduced
noise. This is especiallybeneficial when using
highly efficient speaker systems where the noise
floor could be a problem.

n Easy switching to dual mono mode
In the dual mono position of themode selector, the left-channel
signal is supplied to both speakerterminals, which can be used forbi-amping with dedicated lowrange and high-range drivers.
n Oversize speaker terminals accept also Y lugs orbanana plugs
The sturdy terminals can handle even very large gauge
speaker cable. The
connectors are madeof extruded high-purity
brass material and are
gold-plated for utmost
reliability and minimum
contact resistance.
Y lugs or banana plugs
can also be used.

Bridged connection allows upgrading to a truemonophonic amplifier with 800 watts into
2 ohms (music signals only), 600 watts into
4 ohms, and 300 watts into 8 ohms
Bridged connection results in a monophonicamplifier with four times the power output thanduring stereo operation. This gives effortless
dynamic power.

Unbalanced and balanced input connectors

Output assemblyn Balanced connection prevents induced noisen Input selector button (balanced/unbalanced) on
front paneln Large analog power meters with on/off switch

n Front panelHigh-quality, high-reliability parts

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

800 watts into 2 ohms (✽)
600 watts into 4 ohms
300 watts into 8 ohms
Note: Load ratings marked ✽ apply only to operation with music signals.

m Total Harmonic Distortionn Rear panel

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 loadm Intermodulation Distortion 0.005%
m Frequency Response

At rated output:
At 1 watt output:

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

m Gain (GAIN selector in MAX position)
28.0 dB (stereo and monophonic operation)
m Gain settings

MAX, –3 dB, –6 dB, –12 dB

m Output Load Impedance

Stereo operation:
2 to 16 ohms
Monophonic operation: 4 to 16 ohms[★ With music signals, load impedances of 1 Ω (stereo) or 2 Ω (mono) can be driven.]m Damping Factor

150

m Input Sensitivity(with 8-ohm load)

Stereo operation
Monophonic operation★
A Right/left-channel power meters(dB and % scale)
B Meter operation/illumination switch
ON OFF
C Speaker A/B selector buttons
D Input selector button
BALANCE UNBALANCEE Power switch
F Gain selector
MAX–3 dB
–6 dB
–12 dBG Unbalanced inputs
H Balanced inputs
a: Groundb: Inverted (–)
c: Non-inverted (+)
I Mode selector
DUAL MONO NORMAL BRIDGE
J Right/left-channel speaker output terminals for
A and BK AC power supply 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 depends on the voltage rating
and destination country.

n Supplied accessories:

0.98 V for rated output
0.11 V for 1 watt output
1.95 V for rated output
0.11 V for 1 watt output

m Input Impedance

Balanced:
Unbalanced:

m Signal-to-Noise Ratio(A-weighted, input shorted)

120 dB (GAIN selector in MAX position)
125 dB (GAIN selector in –12 dB position) At rated output

m Output Level Meters

Logarithmic scale, with off switch–50 dB to +3 dB (dB/% Scale)

40 kilohms
20 kilohms

m Power Requirements

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

m Power Consumption

55 watts idle
480 watts accordance with IEC 60065

m Maximum Dimensions

Width 465 mm
Height 180 mmDepth 425 mm

m Mass24.0 kg (52.9 lbs) net
28.0 kg (61.7 lbs) in shipping carton(18-5/16”)(7-1/16”)(16-3/4”)• AC power cord

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

http://www.accuphase.com/F0405Y

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