YAMAHA A-750
¥ 73,800 (released in 1983)
Commentary
Pre-main amplifier equipped with class A turbo.
The Class A turbo circuit is a circuit developed so that pure A-class quality can be obtained even at high power. The Class A turbo circuit achieves both high power and high sound quality by using the pure A-class region for normal operation and the Class A turbo region for large output operation.
The power stage is equipped with Yamaha's original ZDR (Zero Distortion Rule) circuit to improve the distortion and nonlinearity caused by the non-linearity and bias value of the power stage element, and to eliminate the influence of the back electromotive force of the speaker.
The power supply section is equipped with a large-capacity electrolytic capacitor (22,000 μ Fx2) that adopts a hyperfractionation multi-terminal structure.
A GF circuit is mounted to solve the problem of the ground system.
In this circuit, the transformer system, heat sink system, large current system, and signal system are separated, and the common impedance is 0 by making each one point earth which radiates in one place.
A DC servo real-time equalizer is used in the preamplifier section.
With this circuit, an accurate RIAA curve can be generated up to 100 kHz. In addition, the phase shift problem is cancelled out by the CR low-pass filter as the phase goes to the higher frequency region, so that no phase shift occurs as a result.
Equipped with a phono selector and subsonic filter.
Model Rating
| Type | Pre-main amplifier |
| Rated Output (20 Hz ~ 20 kHz) | 140W + 140W (4 Ω, 0.02%) 120W + 120W (6 ohm, 0.005%) 100W + 100W (8 Ω, 0.003%) |
| Input Sensitivity / Impedance | Phono MC : 160 μ V/220 Ω Phono MC : 2.5mV/47k Ω |
| Maximum Allowable Input (1 kHz, 0.01%) | MC:10mV MM:165mV |
| Frequency characteristic | 20 Hz to 20 kHz + 0 -0.5 dB (Aux, DAD) |
| RIAA deviation | Phono MC : 20 Hz to 20 kHz ± 0.3 dB Phono MM : 20 Hz to 20 kHz ± 0.2 dB |
| Total harmonic distortion factor (20 Hz to 20 kHz, 3 V) |
Phono MC - Rec out:0.005% Phono MM - Rec out:0.003% |
| Signal-to-noise ratio (IHF-A network) | Phono MC : 70 dB (equivalent to 250 μ V) Phono MM : 86 dB (equivalent to 2.5 mV) |
| Subsonic filter | 15 Hz, 12dB/oct. |
| Loudness | Continuus |
| Muting | -20dB |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Rated power consumption | 240W |
| External dimensions | Width 435x Height 136x Depth 401.5 mm |
| Weight | 11.2kg |