Denon TU-5.5 (c. 1996)

The Denon TU-5.5 is a compact FM/AM tuner from the mid-1990s, part of Denon's PRESTA mini-system lineup. It was introduced around 1996 at ¥29,000. Its main claim to fame is AM stereo reception, which was already getting rare by then. One Japanese teardown source calls it "an inexpensive tuner whose selling point is AM stereo."

The tuner covers the Japanese FM band (76-90 MHz, no wide-FM support) and AM from 522 to 1629 kHz. It has 30-station random presets, a low-impedance output circuit (500 Ω or less) for clean signal transfer to any amplifier, and two timer functions (Everyday and Sleep). There is also a switched AC outlet that follows the tuner's power state, so it can control other PRESTA components for alarm playback or absence recording. The front panel and power button are aluminum. The LCD display has held up well, with no deterioration and good backlighting.

Inside, the TU-5.5 is a straightforward, cost-conscious design. The FM front end is a packaged unit with a three-gang varicap, feeding a ceramic filter into the LA1265 FM/AM tuner IC. A LA3410 PLL MPX decoder and a TA2040AP AM stereo demodulator follow. The main control is a Hitachi 4-bit microcontroller (HD404729C74S). The teardown notes that adjustment points are very few - "or rather, it's skimpy" - which suggests Denon kept manufacturing costs down by minimizing alignment steps. The board itself is well made, with components neatly laid out.

Performance is described as average for both sensitivity and sound quality in FM, and AM sound quality is in the narrow "radio class." The display, though, is praised for its fine, high-contrast characters. The unit received from a collector in 2016 had drifted slightly in frequency (−0.1 MHz at 80.0 MHz), and realignment corrected it. Measured results after adjustment: stereo separation of 43 dB (L) and 42 dB (R), pilot carrier leakage of −52 dB (L) and −57 dB (R), and audio output level deviation of 0 dB (L) and −0.24 dB (R) in mono. There is no separation adjustment trimmer, and separation still measures reasonably well.

The 75 Ω F-type antenna terminal is a plus, since it is less susceptible to interference. The IC lot numbers date this particular unit to 1997, while the power cable marking says 1996.

• FM: 76–90 MHz, sensitivity 1.2 μV/75 Ω (12.8 dBf), S/N 75 dB (stereo) / 80 dB (mono), THD 0.4% (stereo) / 0.3% (mono), separation 45 dB (1 kHz)
• AM: 522–1629 kHz, sensitivity 18 μV, AM stereo capable
• Power: 100 VAC, 50/60 Hz, 9W
• Dimensions: 250 × 96 × 313 mm (W×H×D)
• Weight: 2.6 kg

AM stereo support makes the TU-5.5 something of a collector's item today, as the teardown source notes. Recorded auction activity is modest - a few Yahoo Auctions listings in late 2025 and early 2025, with bids from ¥1 to ¥3,410, often paired with other PRESTA components like the CDA-5.5 CD player or DRR-5.5 recorder. No long-term reliability reports, competitor comparisons, or broader market pricing data have surfaced. Documentation on this model is thin - essentially two Japanese sources - but what exists is consistent between them.

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