Accuphase P-4500 Power Amplifier

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Stereo Power Amplifer with Outstanding Performance

Since it started from P-300 in 1973, during the past half century, the history of Accuphase Power Amplifiers is continually evolving with a wide range of variations as Monophonic, Class-A and Class-AB. The P-4500 is the succession model of P-4200 launched in 2013. This new model is a direct descendant of the first P-300, not only acting as a strong introduction but realizing the great electrical performance and sound quality coming close to the flagship A-250. The P-4500 features best-in-class low noise and high damping factor performance, and with the enhanced power output stage, it enables to perfectly drive the modern high-end loud speakers.

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.

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.

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Continuous Average Output Power: Stereo operation - 500 watts per channel into 1 ohm, 360 watts per channel into 2 ohms, 180 watts per channel into 4 ohms, 90 watts per channel into 8 ohms. Monophonic operation (bridged connection) - 1000 watts into 2 ohms, 720 watts into 4 ohms, 360 watts into 8 ohms. 

Total Harmonic Distortion: Stereo operation - 0.05% with 2 ohm load, 0.02% with 4 to 16 ohm load. Monophonic operation (bridged connection) - 0.05% with 4 to 16 ohm load

Intermodulation Distortion: 0.01%

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

Gain: 28.0 dB (with GAIN selector at MAX) (Stereo and monophonic operation)

Gain Selection: MAX, -3 dB, -6 dB, -12 dB

Output Load impedance: Stereo operation - 2 to 16 ohms. Monophonic operation: 4 to 16 ohms

Damping Factor: 700

Input Sensitivity: Stereo operation - 1.07 V for rated continuous average output. 0.11 V for 1 watt output. Monophonic operation - 2.14 V for rated continuous average output. 0.11 V for 1 watt output

Input Impedance: Balanced - 40 kilohms. Line - 20 kilohms

Signal-to-Noise Ratio (A-weighted, input shorted): 121 dB (GAIN selector at MAX), 126 dB (GAIN selector at -12 dB) At rated continuous average output

Output Level Meters: -∞ dB to +3 dB (indication in dB and %) Logarithmic scale, with defeat switch, hold time switchable 3 s / ∞

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

Power Consumption: 62 watts idle. 485 watts in accordance with IEC 60065

Maximum Dimensions: Width 465 mm, Height 190 mm, Depth 427 mm

Mass: 29.2 kg net, 35.0 kg in shipping carton