Marantz SM-7
¥ 220,000 (around 1979)
Commentary
A power amplifier developed for Low-TIM.
The main amplifier section consists of a full DC amplifier, and the first stage employs a dual FET source follower amplifier with matching pair characteristics to prevent characteristic degradation due to impedance changes at the input stage. The main amplifier section consists of a dual Tr differential amplifier → emitter follower buffer amplifier, and the power amplifier stage consists of a three stage Darlington circuit with a newly developed Super Hi-fT Tr parallel push-pull.
This Super High-fT transistor was born based on the Low-TIM concept, and is the latest emitter ballast type power transistor at that time, which can be called the crystal of LSI process technology and high-frequency Tr technology.
In spite of the large Pc of 200W, the fT shows 60 mhz. It has excellent high-frequency characteristics, switching characteristics, and stable amplification performance with a margin to the ultra-high band. This is a custom-made Marantz product. As a result, the high-speed response of the SM-7 is remarkably improved over the wide band from the ultra-high band to the ultra-low band.
The power transformer is equipped with a large power transformer that does not vibrate even at the maximum continuous output at the rated load. It has a separate winding structure with the secondary side and left and right channels completely separated.
In addition, a 15000 μ Fx4 large-capacity type capacitor is used to provide a high power of 150W + 150W at ease.
Equipped with a high-precision meter that can directly read the peak output level in dB and wattage at 8 Ω load.
Since the scale is logarithmic compression type, it can be monitored from small output to large output without switching the range.
Equipped with an ASO-detection-type protection circuit that immediately limits the signal to a safe value when the output current or voltage exceeds the safe operating range, protecting the output transistor without compromising the faithful reproduction of the music signal.
Model Rating
Type | Stereo power amplifier |
Rated output | 150W + 150W (8 Ω) 190W + 190W (4 Ω) |
Output bandwidth | 5 Hz to 100,000 Hz |
Total harmonic distortion factor | 0.01% or Less (20 Hz ~ 20 kHz, 8 Ω Load) |
Cross modulation distortion factor | 0.01% or less |
Frequency characteristic | (+ 0, -0.2 dB) : 20 Hz to 20 kHz (+ 0, -1dB) : DC ~ 100 kHz |
Input Sensitivity / Impedance | 1.5V/30k Ω |
Damping factor | 100 or More (8 Ω Load) |
Residual noise | 0.034 mv (IHF-A curve) |
Power consumption | Maximum output : 850W Electrical Appliance and Material Control Law : 400W |
Pwer | 100 V, 50/60Hz |
External dimensions | Width 416x Height 146x Depth 332 mm |
Weight | 22kg |
Sold Separately | Cabinet WC-77 (Walnut Finish) : ¥ 8,000 WC-77N (Mahogany Finish) : ¥ 12500 Dedicated Rack Handle RHA-7 : ¥ 4,000 (1 set) |