Marantz SM-8
¥ 150,000 (around 1982)
Commentary
Stereo power amplifier equipped with Quarter A circuit.
The Quarter A system consists of an input level detection circuit and a high-speed switching circuit. It has a structure in which the bias current is fixed until a certain power (30W for SM-8) is used for complete class A operation, and when the power exceeds the fixed power (30W to 120W for SM-8), it automatically switches to class AB operation.
In addition to realizing the excellent power quality of pure A-class, super high fTBy using a power transistor and unique Low-TIM design, crossover distortion and transient distortion are minimized even during high-power driving of class AB operation.
The basic circuit configuration is a push-pull DC amplifier with a built-in servo circuit.
The power supply section is equipped with a compact but large-capacity transformer and a super audio condenser of 22,000 μ Fx2 + 20,000 μ Fx2 that has been carefully examined in terms of characteristics and sound quality. Heat resistance is improved by filling with special resin.
Using a heat pipe with high heat radiation effect, the stable operation of the power transistor is guaranteed even in class A operation which consumes large current and class AB maximum output.
In addition, a protection circuit is mounted to detect excessive output and keep the power stage within the safe operation range, and the speaker is driven in a stable condition.
The front panel is equipped with a logarithmic compression type peak meter that can directly read the output of 8 Ω load.
The sub-panel is equipped with a switch for changing the recovery hold time of the meter indicator, a selector for driving two speakers simultaneously or independently, and a power switch.
Model Rating
| Type | Stereo power amplifier |
| Rated Output (20 Hz ~ 20 kHz, Simultaneous Operation for Both Channels) | 120W + 120W (8 Ω) |
| Total harmonic distortion factor (20 Hz to 20 kHz, at rated output) | Not more than 0.015% |
| Cross modulation distortion factor | Not more than 0.015% |
| Frequency characteristic | 5 Hz to 100 kHz + 0 -1dB |
| Input Sensitivity / Impedance | 1.5V/47k Ω |
| Damping factor | 100 or More (1 kHz, 8 Ω) |
| Signal-to-noise ratio (IHF-A) | 118dB |
| Rated power consumption (Electrical Appliance and Material Control Law) | 300W |
| External dimensions | Width 474x Height 172x Depth 345 mm |
| Weight | 16.5kg |