SONY ST-S555ES

Commentary

This FM stereo tuner was created with the introduction of original technology to support multi-channel FM and high sound quality.

Equipped with a unique direct comparator that drastically reduces the generation of beats and noise.
In the synthesizer method, the frequency of the receiving station is compared with the local oscillation frequency in phase to keep the tuning stable. This comparison frequency is specified by the processing speed capability of the PLL IC. Conventionally, the frequency close to that of the audio signal is used due to the performance limit of the IC, so there was a fear of noise and beat generation.
The Direct Comparator solves this problem by using a high-speed PLL IC that can directly divide frequencies up to the high frequency range of 220 MHz. As a result, the comparison frequency can be raised to 100 kHz, which is the same as the channel plan. This allows the main stereo signal and 38 kHz sub signal to be separated from each other, greatly reducing noise and beat.
The high-linearity wide-band ratio-detection has been further enhanced by the use of dedicated detection driver ICs. Moreover, the outputs are directly connected to the DC-composite amplifier to provide reliable osae komi between the front and back of the detection transformer, enabling high SN ratio and wide dynamic range.

In order to achieve both high selectivity and high sound quality, WIDE/NARROW IF band switching is installed. In addition, an FET buffer amplifier is used in the final stage of the front end, four uniphase filters with two elements and one package are used. In addition, a differential limiter amplifier is inserted between stages. A differential amplifier equivalent to 10 stages is used. As a result, the pass band has excellent phase characteristics, and the out-of-band is rapidly attenuated.

Audio current transfer is used in the audio circuit. By adopting a current transmission amplification system, mutual interference between L and R channels is eliminated, and the influence of disturbance caused by signal wires is eliminated, realizing clear sound quality.
Since current-to-voltage conversion is performed on the amplifier side of the output cord, freshness is maintained up to the amplifier inlet.
In addition, a DC amplifier configuration and an MPX section with a 3-pole linear phase filter to eliminate unwanted signals have been adopted to reduce distortion.

Two antenna terminals are provided and can be selected by changing the switch. In addition, a -20dB attenuator is mounted on the B series in order to prepare for a strong electric field station.

It uses an 8-station preset mechanism that allows you to call up a station with one touch after making a ドプリセット.
This memory function is a multi-process memory that stores not only station frequencies but also general information such as stereo / monaural MODE, muting ON/OFF, WIDE/NARROW IF band, high blend, antenna selection (gain switching), etc.
This memory IC uses a non-volatile memory that retains memory semi-permanently even when the power cord is removed.

It is possible to tune such as Quick Search (Auto) which automatically searches for a station, Sweep Tune which slowly changes the frequency, and Step Tune which changes the frequency by 100 kHz with one touch.

It is equipped with a program memory function that is linked with ON/OFF of the power switch and allows you to call up specified preset stations one after another.
In this way, the timer set can record two or more and up to four missed calls.

It is equipped with an integrated display that allows you to check at a glance the reception status of the currently receiving station.
The following information is displayed : reception frequency, antenna A/B (attenuator ON/OFF), IF band WIDE/NARROW, high blend ON/OFF, MODE stereo / monaural, muting ON/OFF, program memory 1-4, etc. In addition, the use of a 10-stage electrolytic strength indicator enables detailed reading of electrolytic strength.

It is equipped with a high-blend circuit that improves acoustic sensitivity when radio wave conditions are poor.

It is equipped with front end equivalent to 5 series using FET balance mixer.

Station name display function is installed.

Equipped with a CAL-TONE switch (400 Hz, 50% modulation).

Uses copper-plated copper-tight cases.

Uses a oxygen-free copper power cord with polarity display.

Model Rating

Type	FM stereo tuner
Circuit system	PLL digital frequency synthesizer, quartz lock system Superheterodyne FM tuner
Receiving frequency	76 MHz to 90 MHz
Antenna terminal	75 Ω unbalanced (2 systems)
Intermediate frequency	10.7MHz
SN ratio 50 dB sensitivity	Mono : 1.8 μ V (IHF) / 16.8 dBf (new IHF) Stereo : 22.5 μ V (IHF) / 37.9 dBf (new IHF)
Practical sensitivity	0.9 μ V (IHF) 10.3 dBf (new IHF)
Signal-to-noise ratio	mono:92dB stereo:86dB
Harmonic distortion factor	mono wide: 0.03%(100Hz) 0.03%(1kHz) 0.03%(10kHz) narrow: 0.05%(100Hz) 0.05%(1kHz) 0.05%(10kHz) stereo wide: 0.05%(100Hz) 0.04%(1kHz) 0.12%(10kHz) narrow: 0.07%(100Hz) 0.06%(1kHz) 0.15%(10kHz)
Cross modulation distortion factor	mono wide:0.03% narrow:0.05% stereo wide:0.04% narrow:0.06%
Frequency characteristic	30 Hz to 15 kHz + 0. 2-0. 5 dB
Stereo separation	55dB(100Hz) 60dB(1kHz) 45dB(10kHz)
Effective selectivity (400 Hz)	wide:60dB narrow:90dB
Capture ratio	1.0dB
AM suppression ratio	65dB
Image interference ratio	120dB
IF interference ratio	120dB
Spurious interference ratio	120dB
RF intermodulation interference ratio	88dB(IHF) 105dB(2.4MHz)
Carrier leak suppression ratio	78dB
Muting level	25dBf
Auto-tuning level	25dBf
Output	750mV/620 Ω (After Voltage Conversion by Included ACT Cable)
Pwer	100 VAC, 50Hz/60Hz
Power consumption	23W
External dimensions	Width 430x Height 80x Depth 340 mm
Weight	4.8kg
Attachment	FM ribbon antenna F-type antenna connector Antenna Connector EAC-25 (300 Ω → 75 Ω) Station name display label ACT cable