Accuphase P-4500 – Stereo Power Amplifier

Description

Tecnifi announces the availability of the feature-packed Accuphase P-4500 Stereo Power Amplifier. The quest for the optimal power amplifier has just taken another giant leap forward. The Accuphase P-4500 is feature-packed with an instrumentation amplifier configuration realized with discrete semiconductors in the signal path, triple Darlington 4-parallel complementary push-pull architecture and many other technical advantages. The final outcome 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. An innovatively crafted output protection circuit can also detect any short-circuiting of the speaker terminals, for complete peace of mind. This power amplifier is the most effective tool for immersive music enjoyment on the highest level.

Instrumentation amplifier topology further improves noise performance
The Accuphase 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.

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.

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 progression 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.