Technics ST-S5

Commentary

An FM stereo tuner which realizes faithful waveform transmission up to DC region (DC) by quartz synthesizer system.

A newly developed 28-pin IC with a built-in microcomputer with more than 15,000 elements is used for the PLL circuit and controller of the quartz synthesizer. In addition, the pre-scaler part is also an IC to realize excellent stability and high precision.
As a result, the ST-S5 realizes high stability of local oscillation frequency, and the circuit from the detection stage to the MPX output stage is DC, and amplification, detection and stereo demodulation up to the DC range are realized.
In addition, the reference frequency for stabilizing the local signal is changed from 5 kHz to 25 kHz by the ICs. By setting it out of the range of audibility range, the signal is prevented from leaking into the music signal.

By using a varicap that changes capacitance electrically with DC voltage, the front end is equivalent to a four series varicon. This varicap is especially high-Q back-to-back type and improves the image interference rejection capability of the adjacent station.
In addition, a 4-pole MOS type FET is used for the RF amplifier to realize high sensitivity.

Three ceramic filters with excellent group delay characteristics are used in the IF stage to achieve both high selectivity and low distortion without switching the IF band.

The MPX circuit uses a DC peak sample-and-hold circuit.
The ST-S5 uses a pulse waveform with a fast rising edge as a switching signal, sampling and holding its peak value to improve the separation. In addition, the DC circuit from the detection stage to the MPX output stage maintains a high level of 20 Hz stereo separation, which could not avoid deterioration in the past.

Equipped with a jitter distortion removal circuit.
The ST-S5 uses a steep LC band-pass filter to eliminate jitter distortion, which occurs when the 38 kHz signal demodulated by the MPX circuit is affected by high-frequency audio signals and pilot signals.

It is equipped with a pilot signal cancellation circuit unique to Technics. After being used for stereo demodulation in the MPX circuit, the 19 kHz pilot signal, which is unnecessary for audio reproduction, is removed by electronic circuits.
This circuit uses a PLL IC to inject a shaped -19kHz signal into the MPX input to remove only the pilot signal. In addition, the ST-S5 is equipped with a cancel-level auto-adjuster to prevent variations in the leak carrier, which is the difference between the required cancel amount and the cancel level.

The channel selection can be adjusted in 100 kHz steps for each push of the button by the quartz synthesizer.
It also has preset memories for six FM stations.

Equipped with the last one memory, the station which was received when the power switch was off can be effective when the power switch was on.

Built-in battery backup function protects the memory contents.

The rear panel is equipped with a connection terminal for FM wing antenna.

There is a station index at the bottom of the front panel where you can enter the button number and preset station name.

Model Rating

Type	FM stereo tuner
Receiving frequency	76.1 mhz to 89.9 mhz
Practical Sensitivity (75 Ω)	12.8 dBf (1.2 μ V, IHF' 58)
SN ratio 50 dB sensitivity (75 Ω)	Mono : 16.1 dBf (2.2 μ V, IHF' 58) Stereo : 38.1 dBf (22 μ V, IHF' 58)
Distortion factor	mono:0.06% stereo:0.08%
Signal-to-noise ratio	mono:80dB
Frequency characteristic	20 Hz to 18 kHz + 0. 2-0. 5 dB
Effective selectivity	75dB
Capture ratio	1.0dB
Image interference ratio	95dB(83MHz)
IF interference ratio	105dB(83MHz)
Spurious interference ratio	95dB(83MHz)
AM suppression ratio	55dB
Stereo separation	60dB(20Hz) 60dB(1kHz) 40dB(10kHz)
Leak Carrier (19 khz)	-70dB
Antenna	75 Ω Coaxial Type
Output voltage	0.6V
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	6W
External dimensions	Width 430x Height 53x Depth 234 mm
Weight	3.0kg