| Title | Value |
|---|---|
| Circuit : | DC construction, |
| all stages direct coupled | |
| pure complementary parallel push-pull OCL | |
| Power output : | 2x 110W (1Khz / 8 Ohm / 0,1% THD) |
| 2x 147W (1Khz / 4 Ohm / 0,1% THD) | |
| 2x 100W (20Hz...20Khz / 8 Ohm / 0,1% THD) | |
| 2x 135W (20Hz...20Khz / 4 Ohm / 0,1% THD) | |
| THD : | 0,03% at 1Khz for 100W output |
| 0,02% at 1Khz for 50W output | |
| 0,03% at 1Khz for 1W output | |
| IMD : | < 0,10% (100W, 8 Ohm) |
| < 0,05% (1W, 8 Ohm) | |
| Power bandwidth : | 6Hz...50Khz (-3dB output, 0,1% THD, both channels on) |
| Frequency response : | 7Hz...80Khz (+0 / -1dB, 1W output, 8 Ohm) |
| Damping factor : | > 80 (1Khz / 1W / 8 Ohm) |
| > 40 (DC...20Khz / 1W / 8 Ohm) | |
| S/N ratio : | > 101dB (input short-circuited) |
| Input : | 1V / >47kOhm |
| Output : | 4...16 Ohm (System 1 or 2) |
| 8...16 Ohm (System 1 & 2) | |
| Componentry : | 8 V-FETs |
| 44 transistors | |
| 39 diodes | |
| 2 ICs | |
| PC : | 230W |
| AC outlet : | 1x non switched (300W max.) |
| Dimensions : | 49 x 18 x 24cm |
| Weight : | 20kg. |
| List price : | 230,000¥ (1975...1977) |
JVC JM-S7
october 1975
1977
The other rare V-Fet amplifier... Japan-only, unfortunately.
The JM-S7 uses 4 pairs of NEC Vertical Fet devices (2SK70A / 2SJ20A), thermally-stable FET inputs, 450VA trafo, 2x 22,000µF main caps, temp-stable componentry and superlative build quality.
The large heatsink suggests a Class-A design, and with a lavish 200mA bias current it means it is ! A little hidden engineer's dream novelty is the bias adjustment itself : a DIN-type socket hidden under the little cover plate around the power/speaker buttons allows for easier bias adjustment while the amp is standing upward; not a luxury with top-mounted circuit boards.
[Thank you Oscar !].
According to Shu, major japanese V-FET collector, "The sound of JM-S7 is very good. Its very clear as other V-FET amps and massive as a N7B, but little bit milder (gentle) than Sony's TA-N7B."
The JM-S7 cost 230,000¥ in 1975 and remained exceedingly rare. It still is - TA-N7Bs are abundant in comparison.
The chassis was reused for a 300B tube amp which remained at the protoyping stage in '76.
A real S7 here.
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