Accuphase P-650
¥ 680,000 (released in June 2000)
Commentary
This is a stereo power amplifier that has been developed with the highest grade elements while inheriting the design technology of the past by pursuing low impedance of the amplifier output and constant voltage drive of the speaker.
The output device uses a high-power transistor with a collector loss of 130W and a collector current of 15A, which has excellent characteristics such as frequency characteristics, linearity of current amplification factor and switching.
This device is composed of 6-parallel push-pull and fixed on a heat sink by aluminum die-cast for efficient heat radiation processing.
The amplifier circuit employs a current feedback type amplifier circuit that feeds back the output signal in the form of a current.
The principle of this circuit is as follows : First, the impedance of the input terminal on the feedback side is lowered to detect a current, and the current is converted to I-V (current-voltage) by a transimpedance amplifier to produce an output signal. In this circuit, the impedance of the input terminal on the feedback side is extremely low, so phase rotation hardly occurs and phase compensation is hardly necessary.
As a result, various characteristics can be greatly improved with a small amount of NFB, excellent dynamic characteristics such as start-up, and natural energy response can be obtained.
Mono / stereo / bridge connection can be switched with the mode selector switch on the rear panel side.
In the dual mono position, it can be used as an output for a center woofer or as a bi-amp drive for low and high frequencies.
In the bridge position, the amplifier can be used as a high-output monaural power amplifier by means of a bridge connection. In the bridge connection, two amplifiers of different polarity are fed with opposite phase signals, and speakers are connected to the output terminals of both amplifiers to provide a high output.
The power amplifier circuit uses a printed circuit board made of Teflon (glass cloth fluorine resin) substrate.
Teflon has low dielectric constant, very little leakage current between patterns formed on printed circuit boards, and excellent heat resistance and high-frequency characteristics.
By using Teflon substrate, signal propagation speed is increased due to low dielectric constant, and transmission loss is small, making purer signal transmission possible.
In addition to the usual unbalanced input, the input terminal is equipped with a balanced input that is less susceptible to extraneous induction noise.
The parts through which signals pass are plated with gold.
The P-650 is equipped with a printed board copper foil, a grounding plate through which a large ripple current flows, a capacitor terminal, an input terminal, and a speaker terminal to improve sound quality.
The power transformer employs a newly developed high-power capacity toroidal type of 1000 VA with high-harmonic countermeasures. In addition, it is fixed to a non-resonant aluminum case with a high-efficiency heat radiation structure by using a filler with excellent heat conduction and high vibration damping effect, thereby shielding the external influence.
Toroidal transformers have very low impedance, small size and high conversion efficiency because thick copper wire is wound around a doughnut-shaped core. The P-650 uses a super-ring type in particular, and realizes excellent characteristics because the cross-section of the iron core is close to a circle and the coil is close to a circle and adhesion is good.
The electrolytic capacitor is equipped with two large-capacity 47,000 μ F capacitors.
Large speaker terminals are used for extremely thick speaker cables.
The terminal is made of solid brass, machined into a gold plate, and covered with a mold cap for insulation.
It is equipped with a large power meter and a switch to turn on/off the meter operation and lighting.
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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 |
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| IM distortion factor | 0.003% | ||||
| Frequency characteristic | 20 Hz ~ 20 kHz + 0 -0.2 dB (at rated continuous average output) 0.5 Hz ~ 160 kHz + 0 -3.0 dB (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 : 4 Ω ~ 16 Ω * Only for music signals, stereo 1 Ω and monaural 2 Ω can be loaded |
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| Damping factor | 270 (both for stereo / monaural specifications) | ||||
| Input sensitivity (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) | 120 dB (at input short circuit, rated continuous average output) | ||||
| Output meter | Logarithmic Compression Type with Display / Off Function -50dB to + 3 dB |
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| Pwer | 100 VAC, 50Hz/60Hz | ||||
| Power consumption | 80W (No Input) 625W (Electrical Appliance and Material Control Law) 390W (at 8 Ω load rated output) |
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| Maximum external dimensions | Width 475x Height 223x Depth 491 mm | ||||
| Weight | 38kg |