m Powerful 6-parallel push-pull output stage in each channel delivers
linear power down to very low load impedances m Input stage withMCS topology m Current feedback circuit combines excellent soundquality with total operation stability m Bridged connection mode
allows upgrading to true monophonic amplifier m Massive Super
Ring toroidal transformer rated for 1 kVA m 4-step gain control

Stereo power amplifier is ideal match for C-2400
MCS technology ininput stage improves S/N ratio, distortion ratings and other characteristics.
6 pairs of wide-band high-power transistors in parallel push-pull
configuration for each channel. Massive 1 kVA toroidal power transformer
supports 650 watts of power into ultra-low 1-ohm impedance. 4-step gain
control effectively reduces noise.

Note 1: Low amplifier output impedance
When forming the load of a power amplifier a loudspeakergenerates a counterelectromotive force that can flow back into
the amplifier via the NF loop. This phenomenon is influenced byfluctuations in speaker 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 thecounterelectromotive force generated by the voice coil andprevents the occurrence of intermodulation distortion.

Note 2: Constant drive voltage principle
Even when the impedance of a load fluctuates drastically, theideal power 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 theextremely low load impedance of 1 ohm yields 660 watts. At 2ohms, the figure is 500 watts, at 4 ohms 310 watts, and at 8ohms 171 watts. This demonstrates the impressive performancereserves of this amplifier.

6-parallel push-pull power unit delivers guaranteedlinear power output of 400 watts into 2 ohms, 200
watts into 4 ohms and 100 watts into 8 ohms
The output stage uses high-power transistors witha rated collector dissipation of 150 watts andcollector current of 15 amperes. These devices boast
excellent frequency response, current amplification
linearity, and switching characteristics. The

transistors are arranged in a 6-parallel push-pull
configuration (Figure 1) for ultra-low impedance andmounted on a massive heat sink made from diecast
aluminum. This assures effective heat dissipation
and reduces the impedance of the output stage.
Power linearity is maintained down to ultra-low loads,
which demonstrates the impressive capabilities ofthis amplifier.

Output current (A)The P-5000 continues the distinguished design
policy of the M-8000 and P-7000. This stereo
power amplifier uses carefully selected top
quality parts throughout and is an ideal matchfor the C-2400 preamplifier. MCS topology inthe input stage reduces noise even further.
Refined technology and inspired design resultin superb performance and flawless soundquality.
In order to drive any kind of speaker withprecision 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 these design goals, a power supply
that fully meets the demands of the output
stage is necessary. In the output stage of theP-5000, six pairs of high-power transistors witha rated collector dissipation of 150 watts arearranged in a parallel push-pull configurationfor each channel. The devices are mounted tolarge heat sinks for efficient dissipation ofthermal energy. Rated output power into 1 ohm
is 650 watts per channel (music signals only).
Power remains linear also when impedancechanges, as exemplified by the rating of
400 watts into 2 ohms, 200 watts into 4 ohms
and 100 watts into 8 ohms. Even speakers
with very low impedance or with drastic
impedance fluctuations can be driven
effortlessly and accurately. By using the P-5000
in bridged mode, it is possible to create amonophonic amplifier with even higher power
reserves. This performance is sustained by amassive high-efficiency Super Ring toroidaltransformer and large filtering capacitors.
The important input stage also has been given
due attention. Another Accuphase innovation
called MCS (Multiple Circuit Summing) helps
to minimize noise. Current feedback topology
assures totally stable operation up to very highfrequencies. Balanced inputs shut out external
noise. The copper foil side of the PCBs and all
input and output terminals and major signal
carrying points are gold plated, for enhanced
signal purity.

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

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

MCS topology in input stage reduces residual noiseand 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 are connected inparallel, minimizing noise and distortion and greatly
improving other performance parameters as well.
This approach yields further improved sound quality.

NFB switching type gain control
reduces residual noise

BIAS STABILIZERCIRCUIT

BIAS STABILIZERCIRCUIT

BIAS STABILIZERCIRCUIT

Fig. 1 Circuit diagram of amplifier section (one channel)

Because the current feedback
type amplifier circuitry is very
stable and introduces little phaseshift, an NFB switching gaincontrol has become possible(MAX, –3 dB, –6 dB, –12 dB).
With this approach, reducing gain
also results in reduced noise.
This is especially beneficial whenusing highly efficient speakersystems where the noise floor
could be a problem.

Current feedback circuit topology prevents phaseshifts in high frequency range
The P-5000 employs the renowned current feedback principle developed by Accuphase. At the sensing point of the feedback loop, the impedance is– Input
Buffer+ Input
BufferCurrent
adderI-V
converter
Trans-impedance
amplifierOutputAmplifier

Current NFB
networkFig. 3 Current feedback amplifier principle diagram

kept low and current detection is performed. An
impedance-converting amplifier then turns the current into a voltage to be used as the feedback

signal. Since the impedance at the current feedback point (current adder inFigure 3) isvery low, there
is almost nophase shift.
Phase compensation canbe kept to aFig. 4 Frequency response with current
feedbackminimum, resulting in excellent transient response and superb sonic transparency. Minimal amounts of NFB are used to maximum
effect, providing natural energy response.
Figure 4 shows frequency response for different
gain settings of the current feedback amplifier. Thegraphs demonstrate that response remains uniform
over a wide range.

Robust power supply with "Super Ring" toroidaltransformer and high filtering capacity
The P-5000 features a massive toroidal power transformer with a maximum rating of 1 kVA. The transformer is housed ina non-resonant aluminum case filledwith a material thattransmits heat andabsorbs 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. Two ultra-large aluminumelectrolytic capacitors rated for
47,000 µF eachserve to smooth out the pulsating direct current
from the rectifier, providing more than ample filtering capacity.

n Power amplifier assembly with 6 parallel pushpull transistor pairs per channel mounted directly
to large aluminum diecast heat sinks, MCS
circuitr y, and current feedback amplifierBridged connection allows upgrading to a truemonophonic amplifier with 1,300 watts into 2 ohms
(music signals only), 800 watts into 4 ohms, and400 watts into 8 ohms

n Oversize speaker terminals accept also Y lugs
or banana plugs
The sturdy terminals
can handle evenvery large gauge
speaker cable. The
connectors are madeof extruded highpurity brass material
and are gold-plated
for utmost reliability and minimum contact
resistance. Y lugs or banana plugs can also beused.

Bridged connection results in a monophonic amplifier
with four times the power output than during stereo
operation. Dynamic power with an almost unlimited
feel is the result.
Easy switching between dual mono/stereo/bridged
A mode selector on the rear panel makes it simple
to switch between dual mono,stereo, or bridged operation.
A mode selector on the rear
panel makes it simple to switch
between dual mono, stereo,or bridged operation. Dualmono can be used for example to drive subwoofers
or to obtain the same single-channel signal at bothspeaker terminals, for bi-amping with dedicated lowrange and high-range devices.

Unbalanced and balanced input connectors

n Balanced connection prevents induced noisen Input selector button (balanced/unbalanced) on
front paneln Large analog power meters with on/off switch
n PCB copper foil and all major signal pathcomponents are gold-plated

n Front panel

Assembly with meter and protection circuitryGold-platedparts

High-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
0,650 watts per channel into(both channels driven)
0,400 watts per channel into
0,200 watts per channel into
0,100 watts per channel into
Monophonic operation(bridged connection)

1,300 watts into
0,800 watts into
0,400 watts into

1 ohm(✽)
2 ohms4 ohms
8 ohms2 ohms(✽)
4 ohms
8 ohmsNote: Values denoted by (✽) symbol are for music signals only.

n Rear panelm Total Harmonic Distortion

Stereo operation (both channels driven)
0.05%, with 2 ohm load
0.03%, with 4 to 16 ohm load
Monophonic operation (bridged connection)
0.03%, with 4 to 16 ohm 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 setting: MAX)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, load impedances of 1 Ω (stereo) or 2 Ω (mono) can be driven.]m Damping Factor

270 (also in stereo operation)m Input Sensitivity(with 8 ohm load)

Stereo operation
Monophonic operation★
F Unbalanced inputs
G Balanced inputs

A Left/right-channel power meters(dB and % scale)
B Meter operation/illumination switch
C Input selector
BALANCE UNBALANCE
D Power switch
E Gain selector
MAX –3 dB –6 dB –12 dB

ONOFF

a Groundb Inverted (–)
c Non-inverted (+)
21
H Left/right-channel speaker output terminals
2 2 selector
I Mode2 3 MONO NORMAL BRIDGEDUAL
J AC2 4power supply connector★
25Remarks★ 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:

1.12 V for rated output
0.11 V for 1 watt output
2.25 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

120 dB at rated output (A-weighted, input shorted)m Output Level Meters

Logarithmic scale, dB/% indicationm Power Requirements

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

75 watts idle
630 watts in accordance with IEC-65

m Maximum dimensions

Width 465 mm (18-5/16”)
Height 221 mm (8-11/16”)
Depth 461 mm (18-1/8”)

m Weight

31.2 kg (68.8 lbs) net
37.0 kg (81.6 lbs) in shipping carton• AC power cord

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

http://www.accuphase.com/K0305Y PRINTED IN JAPAN 850-0134-00 (AD1)