SONY ESPRIT ST-J88

Commentary

FM stereo tuner developed as ESPRIT's top-of-the-line tuner.

The Digital Frequency Synthesizer (frequency rigidity) method is further developed from the Crystal Lock method, which suppresses tuning deviation due to aging and temperature changes. As a result, it is possible to realize excellent stability and the performance of each tuner block, and various usability are realized.
In this circuit, a stable reference frequency is generated by a crystal oscillator, and a local oscillation frequency of 100 kHz steps is electronically generated by dividing or mixing it to generate a stable reference frequency. Therefore, all specifications such as distortion factor and stereo separation are always kept in the best condition, and high stability and high accuracy are realized.

In order to take advantage of the synthesizer tuner, it is equipped with automatic tuning and manual tuning that automatically find and select tuning frequency.
In addition to the 7-station preset memory function of the station name display Itazuke, which makes it easy to understand the stored station, you can simultaneously store the reception frequency, mode (stereo / mono), muting (on/off), and selectivity (narrow / normal).

Equipped with a 5-step digital tuning indicator that shows reception status at a glance, it displays signal strength of 20 dBf or higher up to 60 dB in 10 dB steps.

The IF amplifier can be switched between two stages : Normal band using uniphase filter and Narrow band using SAW (surface acoustic wave filter).
SAW is an abbreviation of Surface Acoustic. As an IF filter, it has narrow selectivity while providing ideal amplitude and phase characteristics within the passband.

The front-end features a single-tune with the latest circuit configuration at that time, electronic tuning with a 6-stage varicap with a クォト loop chain method, and a dual-gate MOS FET for the high-frequency amplifier stage and the frequency-mixing section to realize high interference rejection capability, high sensitivity, high Sn, and strong input characteristics.

The MPX circuit achieves high separation and low distortion by using a PLL-IC to cancel the pilot signal and a low-pass filter.

A toroidal transformer is used for the power supply section.

The muting mechanism using a reed relay eliminates inter-station noise without compromising sound quality.

Equipped with two output terminals, fixed and variable.
The terminal is gold-plated.

A 7-segment fluorescent display tube displays digital frequency in 0.1 MHz steps.

Model Rating

Type	FM stereo tuner
Circuit system	FM superheterodyne
Receiving frequency	76.0 mhz to 89.9 mhz
Antenna	300 Ω Balanced Type 75 Ω unbalanced type (coaxial cable connector)
Practical sensitivity	1.8 μ V (IHF) 10.3 dBf (new IHF)
SN ratio 50 dB sensitivity	Mono : 3.2 μ V (IHF) / 15.3 dBf (new IHF) Stereo : 35 μ V (IHF) / 36.1 dBf (new IHF)
Signal-to-noise ratio	mono:80dB stereo:75dB
Capture ratio	normal:1.0dB narrow:1.7dB
AM suppression ratio	60dB
Image interference ratio	110dB
IF interference ratio	110dB
Spurious interference ratio	110dB
Effective selectivity	normal: 25dB(300kHz) 65dB(400kHz) narrow: 65dB(300kHz)
Harmonic distortion factor	mono stereo normal narrow normal narrow 100Hz: 0.04% 0.08% 0.07% 0.3% 1kHz: 0.04% 0.08% 0.07% 0.3% 10kHz: 0.04% 0.08% 0.15% 0.6%
Stereo separation	normal: 50dB(100Hz) 50dB(1kHz) 45dB(10kHz) narrow: 45dB(100Hz) 45dB(1kHz) 40dB(10kHz)
Frequency characteristic	30 Hz to 15 kHz + 0. 2-0. 5 dB
Output Level / Impedance	Fixed Output : 750mV/2k Ω Variable Output : 0 V ~ 1.2V/470 Ω
Semiconductor used	Transistor : 44 pcs MOS FET : 7 IC : 66 Diode : 24 units
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	25W
External dimensions	Width 480x Height 80x Depth 370 mm
Weight	Approx. 7.0 kg
Attachment	Connection code (Equivalent to RK-112) FM feeder antenna F-type coaxial plug Station name display board