Denon TU-332A (c. 1977)
The Denon TU-332A is a solid-state FM/AM tuner from around 1977, sold in Japan for ¥42,000. It's the FM-only TU-332 with an AM section and a built-in 440 Hz test oscillator added. That suggests Denon saw the tuner as a utility component in a tape-based system as well as a way to pull in stations.
The front end uses a frequency-linear 4-gang variable capacitor with a low-noise dual-gate MOS-FET in the RF stage. The IF section relies on a high-integration IC with a multi-stage limiter. Three phase-linear 2-element ceramic filters plus a phase-correction transformer keep phase distortion in check during stereo demodulation, and the MPX stage uses a PLL circuit on a high-integration IC. Denon quoted 1.8 µV practical sensitivity (IHF), 78 dB effective selectivity, and a capture ratio of 1.2 dB. Stereo THD was rated at 0.15% at 1 kHz, with 45 dB separation at 1 kHz and 70 dB stereo S/N.
Denon called the metering a "one-meter indication system." A single meter switches between center-tuning and signal functions, linked to the function switch. In signal mode the zero point shifts to the left edge, so the whole scale is usable. The built-in 440 Hz oscillator outputs 0.5 Vrms, equivalent to 50% broadcast modulation. That made it a handy reference for setting tape deck levels or checking speaker phase and left/right balance. There's also a muting switch, a hi-blend switch for better stereo S/N, and a coaxial FM antenna connector.
On the AM side, it covers 525 kHz to 1,605 kHz with a ferrite bar antenna and an external terminal, using a high-integration IC and ceramic filters. Power consumption is 15 W, and the unit measures 396 × 147 × 281 mm at 5.5 kg.
Documentation on the TU-332A is thin beyond the Japanese catalog sources. There's no service manual, no independent reviews, and no confirmed production run beyond the approximate 1977 date. The engineering side is consistent and detailed, but collector-market data and long-term reliability notes aren't out there yet.
Known specs:
- FM: 76–90 MHz, 10.7 MHz IF
- AM: 525–1,605 kHz, 455 kHz IF
- Output: 1 Vrms at 100% modulation, 1.5 kΩ impedance
- Power: 100 VAC, 15 W
- Dimensions: 396 × 147 × 281 mm, 5.5 kg
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