Sanyo JCX-2900K (1978)
The Sanyo JCX-2900K was a large, heavy stereo receiver of the late 1970s. That is the full designation used in the period test reports, and the measured weight given for the unit was 51 lbs. Nearly everything known about it comes from two receiver test reports published in the summer of 1978. No advertising, service literature or production history has surfaced, so this page is built from what the reviewers measured.
Its most unusual feature was a "Boom Box" subharmonic synthesizer. High Fidelity (September 1978, p.56) tested it and found that it synthesized subharmonics accurately, but it also generated odd-order harmonics of the subharmonic. Feed it a 100-Hz signal and you got the intended 50 Hz plus substantial 150-Hz and 250-Hz tones. The same review noted a quirk in the FM tuning meters. The signal-strength meter showed maximum reading at the point of lowest distortion, while the channel-center meter read well to the right of center, so the two meters did not agree on the best tuning point. The high-blend control was described as modestly effective in reducing high-frequency stereo noise. The mono FM response measured +0, -½ dB from 20 Hz to 15 kHz.
HI-Fi-Stereo-Buyers (July 1978, p.53) measured the amplifier at 120 watts RMS per channel into 8 ohms, both channels driven, 20 Hz-20 kHz at the clipping point. Monophonic distortion was 0.055% THD. Stereo distortion was 0.08% THD, with signal-to-noise at 77 dB. Stereo separation measured 40+ dB, and selectivity was rated very good. The AM tuner drew particular praise because its background noise was notably low. FM performance, measured in the other report (July 1978, p.54), showed full limiting at 2.3 µV, 60-dB mono quieting at 6.5 µV, and 55-dB stereo quieting at 58 µV.
Known specifications, as measured:
- Type: AM/FM stereo receiver
- Power output: 120 W RMS per channel into 8 ohms (20 Hz–20 kHz, both channels driven, at clipping)
- THD: 0.055% mono, 0.08% stereo
- Signal-to-noise ratio: 77 dB
- FM sensitivity: 60 dB quieting at 6.5 µV (mono); 55 dB quieting at 58 µV (stereo)
- Stereo separation: 40+ dB
- Weight: 51 lbs
- Features: Boom Box subharmonic synthesizer, bass turnover (100/200/400 Hz), low/high filters, FM high blend, FM muting, output muting (0/−20 dB), speakers on/off
No production years, original price or further design details have been documented beyond these two test reports.
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