Accuphase P-500L
¥ 530,000 (released in February 1989)
Commentary
This is a stereo power amplifier developed using the development technology of the M-1000 and P-800 with the aim of achieving both high output and small signal reproduction.
The output stage consists of a parallel push-pull circuit in which 10 wide-band transistors with collector loss (Pc) of 150W per channel are connected in parallel to each other. This reduces the impedance to 1/10 of that when a single unit is used. In addition, the total Pc reaches 3000W, enabling output that is not affected by the load even for speakers whose impedance characteristics fluctuate wildly.
In order to improve 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 (a state in which no current flows) by the input signal.
MOS FET, equivalent to non-switching class A drives, is adopted for the front stage driving the last stage, and it is composed of cascode push-pull. Cascode is a circuit used for high-frequency amplification that provides stable operation over a wide frequency band, good input linearity, and enables amplification over a wide dynamic range.
A class A cascode push-pull is also used for the pre-stage of sending a signal to the MOS FET. This realizes a stable output stage with little distortion from a small output in the noise region to a large output in the rated output.
The input stage employs a class A cascode differential push-pull system to improve high-frequency phase characteristics and dynamic range.
Equipped with a bridge switch, it can also be used as a balanced monaural power amplifier by bridge connection.
Normally, a phase inversion circuit is inserted into one amplifier when a bridge is connected. However, with the P-500L, the polarity of the differential input of the two amplifiers is utilized and only the input terminal is switched. Therefore, the circuit configuration is pure without any other amplifier.
The power supply is supplied separately to the output stage and the preceding stage from independent windings of the transformer to prevent mutual interference.
In addition, the front stage consists of dedicated rectifiers and filters for the left and right sides, thereby minimizing interference between the front and rear stages and the left and right channels.
The input terminal is equipped with a full-scale 40k Ω balanced input in addition to the normal 20k Ω phono jack input.
The balance input circuit uses a configuration in which the signal is directly input to the positive and negative inputs of the differential input circuit. In this configuration, it is necessary to insert a level control into each of the positive and negative inputs. However, the P-500L uses a 1 dB step double attenuator with less interlocking error.
The balanced input connector uses an international standard XLR-type connector.
A direct connection method is used for input.
In this method, when a preamp or other device with large DC drift is connected, it is amplified and appears on the output, which may damage the speaker. To prevent this, the DC is cut off by the DC servo method and the DC drift of the amplifier itself due to temperature change is also stabilized.
Equipped with an analog type large power meter, it can directly read the power range of -60dB (0.00027W/8 Ω) to + 3 dB (540W/8 Ω) by logarithmic compression. Also equipped with a switch to turn off the meter operation and lighting.
You can switch between two outputs of the speaker.
In addition, both ends can be connected in parallel with a changeover switch. It is also compatible with a bi-wiring speaker, and each wire can be connected.
Equipped with a natural Persimmon side board on the side.
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Model Rating
| Type | Stereo power amplifier | ||||
| Continuous Average Output (20 Hz to 20 kHz) |
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| Total harmonic distortion factor (both stereo and monaural specifications) |
0.01% (4 Ω ~ 16 Ω) 0.02% (2 Ω) |
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| IM distortion factor | 0.003% | ||||
| Frequency characteristic | 20 Hz ~ 20 kHz + 0 -0.2 dB (Continuous Average Output, Level Control MAX) 0.5 Hz ~ 180 kHz + 0 -3.0 dB (at 1W Output, Level Control MAX) 0.5 Hz ~ 150 kHz + 0 -3.0 dB (Level Control -6dB at 1W output) |
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| Gain | 28.0 dB (both stereo and monaural specifications) | ||||
| Load impedance | Stereo specification : 2 Ω ~ 16 Ω Monaural specification (bridge connection) : 4 Ω ~ 16 Ω |
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| Damping factor | Stereo specification : 500 Monaural specification (bridge connection) : 250 |
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| Input sensitivity (at 8 Ω load) |
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| Input impedance | Unbalanced input : 20k Ω Balance Input : 40k Ω |
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| S/N (A correction Both stereo and monaural specifications) |
120 dB (Input Short, Continuous Average Output) 95 dB (Input 1k Ω, 1W output) |
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| Output meter | Logarithmic compression type -60dB to + 3 dB and output direct reading scale |
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| Semiconductor used | Transistor : 88 FET : 16 IC : 8 Diode : 60 |
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| Pwer | AC100V/117V/220V/240V, 50Hz/60Hz | ||||
| Power consumption | 185W (no input) 980W (Electrical Appliance and Material Control Law) 920W (at 8 Ω load rated output) |
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| External dimensions | Width 481x Height 210 (Including Legs) x Depth 445 mm | ||||
| Weight | 35.0kg |