SONY ST-A7B
¥ 158,000 (around 1977)
Commentary
A high-quality FM/AM tuner that uses a crystal lock system and was developed with the aim of 0 tuning deviation.
The oscillator employs a crystal lock system that divides the frequency of the highly accurate crystal oscillator and locks every 100 100 kHz (0.1 MHz) according to the frequency allocation of Japanese broadcasting radio waves. Unlike conventional continuous oscillation, this system does not require a tuning meter or AFC (Automatic Frequency Control), making it possible to lock the received frequency accurately.
The tuning frequency is displayed numerically, and the Locked indicator lights when the radio wave is locked.
The front-end section uses a low-noise dual-gate MOS FET -GATE MOS FET, a balanced mixer using a dual FET, and a high-precision FM5 series variable capacitor, making the circuit resistant to strong electric fields.
The IF amplifier is equipped with a two stage switching circuit of Normal/Narrow. In the Normal position, a uniphase filter with single-mode group delay characteristics is used, and while obtaining good selectivity characteristics, low distortion rate and high SN are obtained.
In the Narrow position, a uniphase filter is added for higher selectivity.
It is equipped with a beat-cut filter to prevent mixing of minute interference and monkey chatter noise such as unpleasant hiss and jul-jules generated in stereo.
The MPX section uses a PLL IC which is a dual FET differential amplifier multiplied by NFB.
The power supply circuit uses an FET buffer power supply that is also used in Sony amplifiers.
Equipped with a signal / multi-path meter, two LED dial indicators up and down, muting, and high blend switch.
The AM section has an independent structure and uses a tuning knob for AM, drum type dial, AGC circuit and IF filter.
.JPG)
Model Rating
| Type | FM/AM Tuner | ||||
| FM Tuner Section | |||||
| Practical sensitivity of FM | 1.5 μ V (IHF) 8.8 dBf (new IHF) |
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| Signal-to-noise ratio | mono:80dB stereo:75dB |
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| Capture ratio | Normal:0.8dB Narrow:1.8dB |
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| Selectivity (IHF) | Normal:40dB Narrow : Not measurable |
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| Image interference ratio | 110dB | ||||
| IF interference ratio | 110dB | ||||
| Spurious interference ratio | 120dB | ||||
| Distortion Factor (100 Hz, 1 kHz) |
|
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| Stereo separation (1kHz) |
Normal:55dB Narrow:45dB |
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| <AM Tuner Section> | |||||
| Sensitivity (when bar antenna is used) | 250 μ V/m | ||||
| Signal-to-noise ratio | 50dB | ||||
| <General> | |||||
| Power consumption | 43W | ||||
| External dimensions | Width 430x Height 170x Depth 435 mm | ||||
| Weight | 14.5kg | ||||