Accuphase P-500
¥ 510,000 (released in May 1985)
Commentary
A stereo power amplifier developed with AccuPhase's traditional technology for the new era of audio.
The output stage consists of six parallel push-pull transistors with collector loss Pc150W for a total of 12 transistors / ch.
When the power efficiency of the output stage is assumed to be 70%, the theoretical limit output is 4,200W. Therefore, even if the rated maximum output is taken out, there is a sufficient margin to improve the safety of the output stage.
In order to suppress the switching distortion generated at the output stage at the time of small output, the operating point is strictly set so that each element of PNP and NPN is not cut off by the input signal.
A MOS FET equivalent to a non-switching class A drive is used for the front stage of driving the final stage, and it is composed of cascode push-pull. The front stage of sending a signal to this MOS FET is also composed of class A cascode push-pull.
As a result, the output stage is composed of low distortion and stable against load from small output in the noise region to large output in the rated output.
The input circuit constitutes a cascode bootstrap push-pull circuit.
The cascode bootstrap circuit has high gain, excellent high-frequency characteristics, and no degradation of distortion factor even in response to changes in input impedance.
The push-pull configuration of this circuit, together with the wide-band drive stage, improves the element characteristics in the NF loop.
The input section uses a direct connection method.
In addition, in order to prevent damage to the speaker caused by amplification when a pre-amplifier with large DC drift is connected, AccuPhase's original DC servo system is used to cut DC, and the DC drift of the amplifier itself due to temperature change is also stabilized.
In addition to the normal 20k Ω phono jack input, a full-scale 40k Ω balanced input is installed.
Equipped with a subsonic filter that cuts frequencies below 10 Hz.
High-quality elements eliminate sound quality degradation, and the frequency is set to a frequency that does not affect the audible band.
Equipped with a pointer meter that can directly read dB and output watts. Logarithmic compression allows direct reading over a wide power range of -60dB to + 3 dB.
It also has a built-in switch that turns off the meter and lights.
It can be used as a monaural power amplifier with the bridge connection switch.
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Model Rating
| Type | Stereo power amplifier | ||||
| Continuous average power (20 Hz to 20 kHz Strain rate 0.02%) |
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| Total harmonic distortion factor |
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| IM Distortion Factor (SMPTE-IF) | 0.003% | ||||
| Frequency characteristic |
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| Gain | 28.0 dB (both stereo and monaural) | ||||
| Load impedance | Stereo specification : 2 Ω ~ 16 Ω Monaural specification (bridge connection) : 4 Ω ~ 16 Ω |
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| Damping factor (50Hz) |
Stereo specification : 500 Monaural specification (bridge connection) : 250 |
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| Input Sensitivity (8 Ω) |
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| Input impedance | 20k Ω unbalance 40k Ω equilibrium |
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| S/N (A correction Both stereo and monaural) |
120 dB (Input Short, Continuous Average Output) 100 dB (Input 1k Ω, 1W output) |
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| Subsonic filter | 10 Hz, -18dB/oct. | ||||
| Output meter | Logarithmic compression type -60dB to + 3 dB and output direct reading scale |
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| Semiconductor used | Transistor : 82 FET : 10 IC : 8 Diode : 79 pcs |
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| Pwer | AC100V/117V/220V/240V, 50Hz/60Hz | ||||
| Power consumption | 115W (no input) 840W (Electrical Appliance and Material Control Law) 850W (at 8 Ω load rated output) |
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| External dimensions | Width 481x Height 218 (Including Legs) x Depth 445 mm | ||||
| Weight | 33.5kg |