Onkyo Integra T-408 (c. 1977)
The Onkyo Integra T-408 is a quartz-lock FM-only stereo tuner from the late 1970s. It sold in Japan for ¥59,800. English documentation is thin. What survives is a spec sheet on Audio Database and a detailed Japanese repair blog, and both point to a serious, technically ambitious tuner aimed at the domestic market.
The headline feature is the quartz-lock tuning system, which uses crystal oscillation to hold the local frequency deviation to 0.005% or less. The front end uses two MOS FETs in a five-gang FM varicon, with a double-tuned input stage to cut intermodulation interference from adjacent strong stations. The IF stage has two bandwidth positions. Wide mode uses a new four-element linear-phase filter. Narrow mode adds a six-element filter for high selectivity. The first IF stage (wide) uses a MOS FET instead of the usual bipolar transistor or IC, which was an early use of that approach. The MPX section builds a pilot canceler into its PLL IC and extends the low-pass filter cutoff to 23 kHz, pushing the frequency response out to 18 kHz. A ±2-power-supply audio amplifier handles overmodulation cleanly. An air-check calibrator (50% modulation, 440 Hz continuous tone) is built in for setting recording levels. A linear signal meter and a multipath output terminal finish the feature set.
Specs are competitive for the era: 1.8 µV practical sensitivity (IHF, 300 Ω), 80 dB mono / 75 dB stereo signal-to-noise, 50 dB stereo separation at 1 kHz in wide mode, and distortion down to 0.05% mono at 400 Hz. Selectivity is rated at 50 dB (wide) and 85 dB (narrow) at ±400 kHz detuning. The tuner covers the Japanese FM band of 76-90 MHz, weighs 7.2 kg, and consumes 17W.
A Japanese repair blog (hirokun.jp) documents a 2015 restoration of a junk-unit example bought for 1,000 yen. The unit had an intermittent fault. Every 30 seconds to a few minutes, the LOCKED, TUNED, and STEREO lamps would cut out, the T meter would swing fully to the + side, and reception would drop. The cause traced to Q806, a 2SC1583 dual transistor in the T meter circuit. Replacing it with two 2SC1815(GR) transistors fixed the fault. The blog notes the circuit is almost identical to the Onkyo T-7, and the repairer found the quartz-lock action, with the T meter needle dropping to center, genuinely satisfying. Post-repair measurements confirmed good stereo separation, and the blogger calls it an excellent unit in performance and sound quality.
One caution for collectors: this is a Japanese-market tuner (76-90 MHz band), so it won't properly receive US or European FM broadcasts without modification. The "Integra" branding here is Onkyo's own high-end line of the period, not the later Integra-branded home theater separates sold in North America.
Known Specifications
- Type: Quartz-lock FM stereo tuner
- Frequency range: 76–90 MHz (Japanese FM band)
- Practical sensitivity: 1.8 µV (IHF, 300 Ω) / 10.3 dBf
- S/N: 80 dB mono, 75 dB stereo
- Selectivity (±400 kHz): 50 dB wide, 85 dB narrow
- Distortion: 0.05% mono / 0.06% stereo at 400 Hz (wide)
- Stereo separation: 50 dB at 1 kHz (wide)
- Output: 0–750 mV variable
- Semiconductors: 44 transistors, 3 FETs, 6 ICs, 23 diodes
- Dimensions: 438 × 150 × 390 mm; 7.2 kg
- Price (1977): ¥59,800
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