Accuphase P-4500 Stereo Power Amplifier

Accuphase P-4500 Stereo Power Amplifier

Yokohama, Japan | 2020 – The P-4500 is a new addition to the highly acclaimed Accuphase lineup of quality High End Audio Stereo Power Amplifiers.

Stereo power amplifier with outstanding performance


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The quest for the optimal power amplifier has just taken another giant leap forward. The P-4500 features an instrumentation amplifier configuration realized with discrete semiconductors in the signal path, triple Darlington 4-parallel complementary push-pull architecture and many other technology advantages. The result is an impressive S/N ratio of 121 dB, rated output of 500 watts into 1 ohm (music signals), and a damping factor of 700. A newly developed output protection circuit can also detect any short-circuiting of the speaker terminals, for complete peace of mind. This power amplifier is the ultimate tool for immersive music enjoyment on the highest level.

Instrumentation amplifier principle realizes excellent S/N ratio and linear output characteristics

Accuphase P-4500 Power Amplifier Stage

Instrumentation amplifier topology further improves noise performance
The P-4500 employs an instrumentation amplifier configuration that is highly effective in keeping external noise from affecting the signal transmission lines. The configuration comprises a signal input unit that receives the signal from the preamplifier and a power amplification unit that sends power to the speakers. The input stage is designed for high gain (22 dB) and the power amplification stage for low gain (6 dB). Consequently, the internal signal has a large amplitude which makes it much less prone to interference, thereby further improving the noise performance.


MarleyAccuphase P-4500 Stereo Power Amplifier
Accuphase P-4500 Stereo Power Amplifier

Signal input section with high gain
As in the A-75, the signal input stage is entirely configured with low-noise discrete circuit components which can handle high power supply voltages. This makes it possible to design the circuit for a high gain of 22 dB, something that cannot be achieved with OP amp ICs that have power supply voltage constraints. As a result, the S/N ratio of the P-4500 is an astonishing 121 dB.

Accuphase P-4500 Stereo Power Amplifier

Power amplification section with linear output characteristics
The power amplification stage of the P-4500 features bipolar power transistors mounted directly to large heat sinks for highly efficient thermal dissipation. The devices are configured as a triple Darlington 4-parallel complementary push-pull circuit that is capable of doubling the rated output when the impedance is halved. In other words, it achieves a fully linear power progres- sion of 90 watts into 8 ohms, 180 watts into 4 ohms, and 360 watts into 2 ohms. It can even supply loads as low as 1 ohm with 500 watts of power (music signals). The impressive damping factor of 700 means that the amplifier has ample leeway to drive any kind of loudspeaker.

Functionality – Convenience that makes sense

Accuphase P-4500 main Selector

Advanced Features

  • 4-parallel complementary push-pull configuration using bipolar power transistors
  • Linear output characteristics (90 W / 8 ohms, 180 W / 4 ohms, 360 W / 2 ohms)
  • 500 W output into ultra-low impedance load of 1 ohm (music signals)
  • Strong power supply with massive toroidal trans-former and large 50,000 μF filtering capacitors
  • Instrumentation amplifier principle
  • High-gain signal input section for outstanding S/N ratio
  • Dedicated power supply for signal input section ensures stable operation
  • Line and balanced input connectors
  • Polarity switching for balanced input connectors
  • MCS+ circuit topology further reduces noise
  • Current feedback principle in amplification circuitry
  • Protection circuitry using MOS-FET switches
  • High damping factor of 700
  • Balanced Remote Sensing
  • Speaker output protection with over-current detection
  • Highly responsive large peak power meters
  • Two sets of large speaker terminals
  • 4-step gain controlSupport for bi-amping and bridged mode
Accuphase P-4500 inside
Accuphase P-4500 Stereo Power Amplifier
Accuphase P-4500 Stereo Power Amplifier

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