Onkyo Integra T-425 (c. 1981)
The Onkyo Integra T-425 is a quartz digital synthesizer FM/AM stereo tuner from around 1981. It was priced at ¥39,800 in Japan. It's slim, just 66mm high and 3.4kg, and it carries a solid set of reception features for its size.
The tuning system is a PLL controlled by a microcomputer, with the reference frequency locked to a crystal oscillator. Frequencies are set digitally in 100 kHz steps. You can step manually in 0.1 MHz increments or hold the switch for auto-scan. Twelve station presets (6 FM, 6 AM) keep their memory even with the power cord unplugged. The RF stage uses a dual-gate MOS FET, the IF section a wide-band linear phase filter, and the MPX stage a PLL IC. That was fairly standard high-end practice for the era, but executed with care. A three-step delayed AGC and a noise reduction circuit that blends L/R high frequencies on weak signals round out the package.
Performance figures are respectable. FM sensitivity is 0.9 µV (10.3 dBf), capture ratio is 1.0 dB, mono S/N is 76dB and stereo is 72dB, and stereo distortion is 0.2% across 50 Hz - 10 kHz. The AM section is fully independent from the RF stage through audio, with its own loop antenna. Fixed output is 500mV/1.6kΩ.
Documentation on this model is thin. The record consists of its Japanese-market spec sheet and a handful of used listings. One current Japanese listing shows a used unit at ¥11,000. There's no documented owner commentary, no service history, and no detail on how it sat within Onkyo's broader Integra lineup of the period.
Known specs:
- Type: Quartz digital synthesizer FM/AM stereo tuner
- FM range: 76.1–89.9 MHz (Japanese FM band)
- FM sensitivity: 0.9 µV / 10.3 dBf (IHF, 75Ω)
- S/N: 76dB mono / 72dB stereo
- Presets: 12 (6 FM + 6 AM), non-volatile
- Dimensions: 435 × 66 × 278 mm; 3.4 kg
- Original price: ¥39,800 (c. 1981)
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