Accuphase P-450
¥ 380,000 (released in April 1997)
Commentary
This is a stereo power amplifier that combines the power amplifier technology that Accuphase has accumulated and uses the highest-grade elements that have examined each part individually and a current feedback amplifier circuit.
The output stage uses a newly developed high-power transistor with collector loss of 150W and collector current of 15A.
This element has excellent characteristics such as frequency characteristics, linearity of current amplification factor, switching, etc. It is composed of 4-parallel push-pull. By attaching it to a large heat sink made of aluminum die-cast, efficient heat radiation processing is carried out and stable large output is realized.
It uses a current feedback amplifier circuit that feeds back the output signal in the form of current.
The operating 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 into I-V (current-voltage) by a transimpedance amplifier to produce an output signal.
In this circuit, since the impedance of the feedback input part is extremely low, phase rotation hardly occurs and phase compensation is hardly necessary. Therefore, various characteristics can be greatly improved with a small amount of NFB, and dynamic characteristics such as rising are excellent, and sound quality is improved by natural energy response.
Equipped with a changeover switch, it can be used as a monaural power amplifier by bridge connection.
Bridge connection is a method in which two channel amplifiers are supplied with signals of the same voltage and opposite phases, and speakers are connected to the output terminals of both amplifiers to improve sound quality and obtain high output.
The input terminal is equipped with a balanced input terminal to eliminate interference noise from signal cables between devices.
The power supply section uses a large toroidal transformer of approximately 660 VA.
Toroidal transformers have features such as extremely low impedance, small size and high conversion efficiency because thick copper wire is wound around a doughnut-shaped core. The P-450 uses a super-ring-type transformer in particular. Because the section of the iron core is close to a circle and the coil is close to a circle and adhesion is good, loss is small, weight is light, leakage flux under load is small, and groaning and vibration are small. In addition, iron loss and inrush current are small because the section of the iron core is small and the weight ratio of the copper wire is large.
The aluminum electrolytic capacitor is equipped with two large capacity types of 47,000 μ F/80WV.
High-purity copper is used for the components through which signals pass. The P-450 is plated with gold to improve the sound quality of the earth plate, capacitor terminal, input terminal and speaker terminal through which a large ripple current flows.
Since the input terminal, which is frequently used, is thin with an ordinary gold plate, it is treated with about 10 times the thickness for industrial equipment to improve reliability.
Equipped with an analog type large power meter that can directly read a wide power range by logarithmic compression.
It is also equipped with a switch to turn on/off the meter operation and lighting.
Large speaker terminals are used for extremely thick speaker cables.
It is made of solid brass, machined into a gold plate, and covered with a mold cap for insulation.
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Model Rating
| Type | Stereo power amplifier | ||||
| Rated 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 (bridge connection) : 4 Ω ~ 16 Ω |
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| Damping factor | Stereo specification : 400 Monaural specification : 200 |
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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, input short) | 120 dB (at rated continuous average output) | ||||
| Output meter | Logarithmic compression type peak level display Output direct reading at dB scale and 8 Ω load |
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| Pwer | 100 VAC, 50Hz/60Hz | ||||
| Power consumption | 125W (no input) 450W (Electrical Appliance and Material Control Law) 630W (at 8 Ω load rated output) |
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| Maximum external dimensions | Width 475x Height 211x Depth 465 mm | ||||
| Weight | 30.6kg |