YAMAHA A-4D
¥ 39,800 (around 1982)
Commentary
A pre-main amplifier developed using Yamaha's amplifier technology.
In the equalizer section, a differential input by FET is used for the first stage and a low-noise, wide-band IC operational amplifier is used for the last stage. This eliminates the input capacitor which adversely affects sound quality.
In addition, MC cartridge can be used by gain switching method.
The tone control amplifier uses the Yamaha NF-CR type to reduce sound quality degradation, and the NF attenuation MIX type eliminates clicks near the center.
The power amplifier uses a differential-input hybrid IC for the voltage amplifier stage and a discrete two stage Darlington SEPP-OCL circuit for the power amplifier stage.
Equipped with a microphone mixing function. By adding auto-level control (ALC) to a high-sensitivity FET-input microphone amplifier and adopting a balanced mixing circuit, excellent sound quality can be obtained. In addition, the source and microphone levels can be and recording effects such as fade-in and fade-out can also be controlled.
A protective circuit by relay is mounted.
In consideration of sound quality, constant voltage is supplied to each indicator with a separate winding.
Model Rating
| Type | Pre-main amplifier |
| Rated output | 40W + 40W (20 Hz ~ 20 kHz, 8 Ω, 0.02% distortion) |
| Frequency characteristic | 20 Hz ~ 20 kHz -0.2 dB (Phono MM → Rec out) |
| Total harmonic distortion rate (20 Hz to 20 kHz) | MM:0.003% MC:0.005% |
| RIAA deviation | MM : + / - 0.3 dB |
| Total harmonic distortion rate (20 Hz to 20 kHz) | 0.015% (Aux, Tape, Tuner → Spout, 20W, 8 Ω) |
| Signal-to-noise ratio (IHF-A network) | MM:86dB MC:70dB Tuner:100dB Mic:55dB |
| Pwer | 100 VAC, 50Hz/60Hz |
| Rated power consumption | 80W |
| External dimensions | Width 435x Height 112x Depth 299.5 mm |
| Weight | 5.9kg |