Sansui TU-666 (1970)
A solid-state AM/FM stereo tuner with high-end performance and refined circuit design from Sansui's early 1970s lineup.
Overview
The Sansui TU-666 is a solid-state AM/FM stereo tuner produced in 1970, designed for high-fidelity reception with advanced features for its time. It delivers strong FM and AM performance, using a carefully engineered front end and stabilized power supplies to minimize drift. The tuner was originally priced at ¥33,800 and is noted for its excellent build quality, clean internal wiring, and thoughtful design refinements over earlier models like the TU-555. It features a round analog tuning scale with a green-lit "fantastic illumination dial" made of smoked acrylic, and includes a stereo indicator lamp.
Specifications
| Receiving frequency (FM) | 76 MHz to 90 MHz |
| Receiving frequency (AM) | 535 kHz to 1605 kHz |
| Sensitivity (FM, 20 dB quieting) | 2 μV |
| Sensitivity (FM, IHF) | 2.5 μV |
| Sensitivity (AM) | 20 μV |
| Total harmonic distortion (FM) | 0.8% |
| Signal-to-noise ratio (FM) | 65 dB |
| Selectivity (FM) | 45 dB |
| Selectivity (AM) | 25 dB |
| Capture Ratio (IHF, FM) | 3 dB |
| IF Rejection (FM) | 60 dB or more |
| Image Frequency Rejection (FM) | 55 dB or more |
| Image Frequency Rejection (AM) | 40 dB or More (1000 kHz) |
| Spurious response rejection (FM) | 60 dB or more |
| FM stereo separation | 35 dB or More (400 Hz) |
| Unwanted radiation (FM) | 34 dB or less |
| Antenna input impedance (FM) | 300 Ω (Balanced), 75 Ω (Unbalanced) |
| Output level | 0.7V |
| Semiconductor count | Transistor: 24, FET: 1, IC: 1, Diode: 19 |
| Power supply voltage | 100 V, 50Hz/60Hz |
| Power consumption | 15W |
| Dimensions | 335 mm (W) x 127 mm (H) x 278 mm (D) |
| Weight | 5 kg |
Design
The TU-666 uses a FET in the FM front-end and a frequency linear type 3-row varicon, contributing to stable tuning and equally spaced frequency calibration. The IF stage employs a 4-stage IF and 3-stage limiter using a single IC, while the MPX circuit includes an SCA filter and an LC-type carrier leak filter. A novel method replaces the conventional high-cut filter to improve reproduction of frequencies above 10 kHz. The tuner features pure electronic FM stereo/mono switching with automatic stereo detection in FM AUTO mode, and a muting circuit to suppress inter-station noise. The AM section uses a large ferrite bar antenna and a ceramic filter. Power supplies for the FM front-end and IF stages include ripple filters for stabilization, and the output circuit has a semi-fixed level adjustment. The tuning scale is a round analog type with a green-lit smoked acrylic dial.
Market
Common issues include FM front-end instability due to poor soldering by Alps and power supply fluctuations, which can cause tuning drift. All electrolytic capacitors are expected to be out of specification after 50 years and should be replaced. Adding a 1 Ω, 5 W resistor in series with the dial lamps can reduce heat and soften the illumination.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.
Related Models
- Sansui sax-200 (Late 1970s)
- Sansui sax-600 (Late 1970s)
- Sansui sr-222 (1973-1975)
- Sansui sr-717 (1974-1976)
- Sansui sr-2050c (1975-1977)
- Sony ps-5550 (1978-1980)
- Sony ps-lx5r (1983-1985)
- Sony ss-7220a (1970s)
- Sony ss-97 (Late 1970s (approximately 1977-1979))
- Sony ss-999 (Late 1970s (approximately 1977-1979))