Sansui TU-555 (1968)
A solid-state FM/AM tuner released in June 1968 with advanced drift compensation and a pure electronic stereo switching system.
Overview
The Sansui TU-555 is an FM/AM tuner produced in June 1968. It has a 3-gang FM tuning capacitor and an FET-based RF stage for better reception. Distortion is low and selectivity is high on both FM and AM. It has a stereo indicator, a muting switch and a large tuning meter for lining up stations. The unit was praised for its excellent FM sound and reception quality, described as "a real high-end product of its time."
Specifications
| Receiving frequency (FM) | 76 MHz to 90 MHz |
| Sensitivity (FM) | 2.5 μV (IHF) |
| Harmonic distortion factor (FM) | 0.8% or less |
| Signal-to-noise ratio (FM) | 60 dB or more |
| Selectivity (FM) | 45 dB or more |
| Capture Ratio (IHF) | 3.0 dB |
| Image ratio (FM) | 50 dB or more |
| IF Rejection (FM) | 60 dB or more |
| Spurious Radiation | 34 dB or less |
| Spurious response rejection | 60 dB or more |
| FM stereo / separation | 35 dB or more |
| Antenna input (FM) | 300 Ω balance; 75 Ω unbalance |
| Receiving frequency (AM) | 535 kHz to 1605 kHz |
| Sensitivity (AM, IHF) | 20 μV |
| Image ratio (AM) | 40 dB or More (1 MHz) |
| IF Rejection (AM) | 60 dB or More (1 MHz) |
| Selectivity (AM) | 20 dB or More |
| Output Level / Impedance | 1.5 V / 10k Ω or More |
| Power supply voltage | 100 VAC, 50Hz/60Hz |
| Power consumption | 10VA |
| External dimensions | 292 x 111 x 267 mm (W x H x D) |
| Weight | 3.9kg |
| Tuning Bands | FM, MW (AM) |
| Tuning Scale | Analogue |
Design
The TU-555 uses FET and a 3-row varicon in its FM/AM tuner design. The FM front-end has the 3-row varicon and an FET in the RF stage. The AGC circuit improves selectivity in strong electric fields, and a 4-stage IF amplifier and 3-stage limiter handle strong signals. Power supplies for the FM and AM sections are stabilized with zener diodes. The design needs no AFC circuit because it compensates for temperature drift. The stereo decoder uses filter-hybrids like the FP-38A. The FM stereo/mono switch is pure electronic, with automatic switching via FM-AUTO when broadcasts change from mono to stereo. There are both short- and long-range FM antenna attenuators, a high-sensitivity ferrite bar for AM, and switchable output levels. Alps manufactured the FM and AM front-ends.
Market
Original pricing was ¥28,900 at release. Common issues are degraded electrolytic capacitors and awkward internal wiring. Repairs typically mean replacing all the electrolytic caps and servicing the stereo decoder, such as replacing defective filter-hybrids. A separate wood case, model C-10, was available. Setup requires adjusting the FM-MPX separation on the back panel.
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Related Models
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- Kenwood KR 4070 (1977-1979)
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