YAMAHA AX-640
¥ 49,800 (released in 1990)
Commentary
A pre-main amplifier with simple and straight design.
The LiD (Low-Impedance Drivability) power supply is designed to support the high dynamic range of digital sources and to provide a stable power supply independent of signal frequency and speaker impedance.
As a result, a low-impedance drive capability with a margin is obtained.
By separating the pre-part and power part with different functions and making each part independent, mutual interference is reduced.
In addition, the power supply is an independent power supply, and a regulator is installed in the pre-section, which handles small signals, in order to realize signal transmission that maintains a clean state.
Equipped with CD direct position and tone direct switch.
With CD Direct, the music signal is directly input to the main volume. When tone bypass is ON, all inputs pass through the tone control and are directly connected to the power amplifier section.
High-quality metal-coated resistor is used for signal parts.
In addition, gold plating is used for the CD input pin plug and speaker output terminal, and OFC power cord and GT leg are used.
It has six inputs with VCR/AUX for VCR.
In addition, it is equipped with continuous loudness, which compensates for the lack of volume in the low range according to the volume during small volume listening.
Not only normal speaker drives, but also Yamaha active servo speakers are supported.
Yamaha Active Servo Technology is realized by the Helmholtz resonator theory on the speaker side and the negative impedance Kudo circuit on the amplifier side, making it possible to achieve excellent low-frequency playback even in small systems regardless of the size or shape of the speaker.
There are 2 variations of body color, titanium color and black.
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Model Rating
| Type | Pre-main amplifier |
| Rated Output (20 Hz ~ 20 kHz) | 105W + 105W (6 ohm, 0.015%) |
| Input Sensitivity / Impedance | Phono MC : 160 μ V/220 Ω Phono MM : 2.5mV/47k Ω CD, etc. : 150mV/47k Ω |
| Total harmonic distortion factor (20 Hz to 20 kHz) |
Phono MC:0.007% Phono MM:0.003% |
| S/N ratio (IHF-A) | Phono MC:70dB Phono MM:86dB CD and others : 102 dB |
| Practical S/N ratio | 110 dB (CD, etc., Vol-22.5 dB) |
| Tone control | Bass : ± 10 dB (350 Hz) Treble : ± 10 dB (3.5 kHz) |
| Continuous loudness | -40dB (based on 1 kHz, maximum correction amount, listening correction curve) |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 185W |
| External dimensions | Width 435x Height 139x Depth 330.5 mm |
| Weight | 9kg |