Sony ST-J55 (1979–1981)
A digitally tuned AM/FM stereo tuner using a crystal-locked synthesizer system, produced by Sony from 1979 to 1981.
Overview
The Sony ST-J55 is a synthesizer tuner made in Japan between 1979 and 1981. It supports FM, MW, and LW bands with digital tuning managed by an internal microprocessor. Known for precise frequency control, it was positioned as an accessible model in Sony’s tuner lineup, sometimes referred to as "the baby" of the range. The unit features an 8-station random preset memory that stores muting and stereo/mono settings per station, along with multiple tuning modes for flexible station selection.
Specifications
| Practical sensitivity | 1.8 μV |
| Effective selectivity | 85dB |
| Spurious interference ratio | 100dB |
| Power consumption | 12W |
| External dimensions | 430mm (W) x 80mm (H) x 325mm (D) |
| Weight | 3.7kg |
Design
The ST-J55 uses a crystal lock digital synthesizer system for channel selection, with a VCO-based local oscillation circuit that changes frequency in 100kHz steps for FM and 9kHz steps for AM. A PLL method compares the oscillation frequency to a crystal oscillator reference for stability. Frequency is displayed on a 7-segment white fluorescent indicator. The tuner includes CAL-TONE and a notch filter, and offers four tuning speeds: direct random, quick search, sweep, and step.
Context
Described as "the baby" in Sony’s tuner lineup, the ST-J55 offered core digital tuning features in a more compact and affordable form compared to higher-end models.
Market
Originally priced at ¥49,000 in Japan around 1979, the ST-J55 was later listed for $75 in a 1991 US magazine, indicating its presence in secondary markets.
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