CLASS-AB STEREO
POWER AMPLIFIER

P-7500Accuphase Laboratory, Inc.

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The history of Accuphase could be said to be “the history of the highpower amplifier.”
The P-300, launched back in 1973, was the epoch-making power amp
with the excellent output power of 150W/8Ω, 200W/4Ω and surprised
audiophiles worldwide with its terrific speaker driving ability.
The new P-7500 of P-300 descent is the flagship of Accuphase Class
AB power amplifier, and the P-7500 is the 4th generation model since
the P-7000 in 2003. It unites the largest-ever output power and thestate-of-art technologies in the historical Accuphase power amp family.
With the overwhelming output power of 300W@8Ω / 600W@4Ω, theultra-low noise characteristic that shows the 11% improvement from theformer model, and the super-high damping factor of 1000, the new P7500 is born here, investing all engineering efforts that now Accuphaseretains.
In addition, the P-7500 ensures product safety with the well-enhanced
protection circuitry to prevent a short-circuited accident at speakerterminals.
The P-7500 brings out the best of any speaker, allowing you to enjoy
never –before experienced soundscapes.
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Dimensions and Weight• Unit dimensions are the same as P-7300
Weight is slight heavier– Width 465mm– Height 238mm– Depth 515mm– Weight 49.0kg

Accuphase Laboratory, Inc.

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The dimension of the P-7500 is same as the P-7300, andthe weight is a little heavier, it weighs 49kg.
** P-7300: Width 465mm, Height 238mm, Depth 515mm,
Weight 48.6kg

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Front and Rear View
High sensitivity needle power meterTwo pairs of large speaker terminals

Front View

Rear ViewMeter Display Selector

Accuphase Laboratory, Inc.

3The P-7500 tidies up the very traditional design of theAccuphase power amplifier with massive and elegant
impressions.
The large analog “needle” meters which offer output powermonitor and good visibility, are located in the front panel,
They are high-sensitivity with the -50dB indicator, whichallows you to enjoy the upbeat needle move even under thelow volume operation.
We also put the gain selector in the front panel,
You can choose the appropriate gain level from the 4settings, “Max, -3dB, -6dB, and -12dB.”
This gain switching does not attenuate the signals with anattenuator. But it controls the gain at the input amplifier
section, making the power amplifier section stable andreducing the residual noise when using the high-efficiency
loudspeakers. We can simultaneously decrease the noise,
which occurs when operating the unit under a low gain level.
You can easily make a bi-wiring or bi-amping connection withthe two large speaker terminals.

3Internal View
High-efficiency large troidal transformer

Lch Power amp block

Rch Power amp block

60000uFCustom madeFilter Capacitor

Accuphase Laboratory, Inc.

4P-7500 has a mono-block construction.
It contains an intense power supply with a massive
special made high-efficiency toroidal transformer and twosizeable 60000μF special made filtering capacitors in theunit's center.
In addition, the two power amplifier units are kept
separate for the left and right channels.

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High Output Power• Class-AB 300W / 8Ω, 900W / 2ΩP-7300P-7500

8Ω
4Ω
2Ω

125W

300W

250W

600W

500W

900W

Rated Output power

Accuphase Laboratory, Inc.

5High power design provides the rated output power of
300W/8Ω, 600W/4Ω, and 900W/2Ω that vastly exceeds
conventional models, securing an overwhelming dynamicrange.

5Technology for High Output Power• 10 Pararrel Output stage per channel

Glass cloth fluorocarbon
resin printed circuit
board

Gold-Plated bus bar
High output Bipolar transistor(150W 15A)

Power Amplifier Engine

Accuphase Laboratory, Inc.

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The P-7500 power amplification stage uses a 10-parallelpush-pull power transistor architecture, providing a large
current without the influence of impedance fluctuation ofloudspeakers.
The Gold-plated glass cloth fluorocarbon resin PCB
helps to improve a lower impedance and reliability.
The gold-plated big bus bars are on the paths wherelarge current flows. They contribute to the further lower
impedance for the circuits and allow ample output power
to be transmitted to the loudspeakers.

6Ultra Low Noise• Highest S/N out of power amplifiers– S/N ratio: 130dB guarantee (P-7300: 125dB)

P-730018uV

P-750016uV
11% Down
Actual output noise

Accuphase Laboratory, Inc.

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The noise performance of the P-7500 is remarkable
compared with the former P-7300.
With the state-of-art circuitry, the P-7500 improves noiselevel suppression by 11% over the previous model.
The guaranteed S/N ratio achieves 130dB, the bestvalue in the Accuphase Power Amp history.

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Technology for ultra low noise• Instrumentation Amplifier architecture• Balanced signal transfer with the optimization ofgain distribution

Balanced Input Module

Signal Input Section

Accuphase Laboratory, Inc.

8With balanced circuits in the signal input section, theamplification stage is comprised entirely of andinstrumentation amplifier principle that equalizes input
impedance on the + and – sides, for excellent external
noise suppression, and providing optimal circuitry for thishigh-end audio amplifier.
Noise Level suppression has been dramatically improvedby assigning a high gain (12.6x) in the signal input
section with excellent noise figure results.

8Super high Damping-Factor• Same Damping-Factor as Top models– Damping Factor: 1000 guaranteed

A-250

1000

P-7500

500
1000
1000

800

Guaranteed Damping-Factor
800

Accuphase Laboratory, Inc.

9The P-7500 achieves 1000 of guaranteed DampingFactor, equal to the flagship Class-A monophonic power
amp A-250.

*Damping-Factor, DF: The damping factor is an index ofspeaker driving ability. A Higher Damping-Factor
amplifier has a higher speaker driving ability. DF = 8 ohm/ Output-impedance

9Technology for super high Damping Factor• Speaker protection equipped with MOSFET switch circuit• Short signal path configuration

Large speaker terminals

Protection circuit Assembly

MOS-FET switch
On-resistance: 1.6mΩ

Accuphase Laboratory, Inc.

10Mechanical relays are the typical components forspeaker protection. Still, the contact resistance of
mechanical relay is higher than people think.
Therefore, Accuphase has chosen the MOS-FET switch
instead of conventional mechanical relays for speakerprotection.
Thanks to this MOS-FET switch, the damping factor,
reliability, and sound quality are improved.
The P-7500 employs carefully-selected very lowimpedance components such as the large speakerterminals. Making signal paths thick and short also helps
attain low impedance.
** MOS-FET switch On-resistance
P-7500’s MOS-FET: 1.6mΩ
P-7300’s MOS-FET: 2.0mΩ

10Technology for super high Damping Factor• Balanced Remote-sensing– Feedback from speaker terminal proximity– Signal-line and GND-line sensing
Signal sensing
Speaker terminal+ Signal- GND
Power Amplifier

GND sensing

Accuphase Laboratory, Inc.

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Remote Sensing is the technique to lower the amplifier's
output impedance by the negative feedback with signal
sensing from nearby the speaker terminals.
Balanced Remote Sensing is the technique to make theoutput impedance even lower by both the signal sensing
and the GND sensing, that is, the negative feedback ofthe GND level.
Not only the Damping Factor but also the Total Harmonic
Distortion and Intermodulation Distortion are all improvedby the Balanced Remote Sensing.

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Pursuing further product safety and reliability• Power amplifier– Newly-developed protection circuit using Photo-couplers– Temperature-sensors are installed on the heatsink
Temperature-sensor
Photo-coupler

Temperature-sensor

Accuphase Laboratory, Inc.

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The newly designed output protection circuit can detect
any short-circuiting of the speaker terminals with due
consideration for product safety.
Temperature sensors that detect the heatsink
temperature are installed (2 sensors on a heatsink).
Thanks to this, the unit accurately ascertains the hightemperature alarm in the power amplifier section.
Thanks to the photo-coupler, the detected signal iscompletely isolated from the output signal to minimize
the adverse effects on the sound quality.
**When these protection circuits are activated, the unit
completely interrupts speaker output. It makes the power
meters flash to indicate the abnormal condition.

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