YAMAHA T-1
¥ 60,000 (around 1977)
Commentary
An FM/AM tuner that combines excellent audio characteristics with high selectivity.
The basic circuit configuration consists of front end using 4-row varicon and MOS FET, Local-Auto DX2-stage IF stage, wide-range balanced type ratio detector, DC / NFB / PLL / MPX circuit with level-following pilot cancel circuit, and audio stage.
The AM section uses a 3-row varicon and consists of a tunable RF amplifier, differential mixer, IF circuit, and peak-to-peak detector.
The front end is equipped with a high-precision frequency linear type 4-row varicon with double tuning between stages. The RF amplifier is equipped with a low-noise MOS FET with excellent high-frequency characteristics to realize high sensitivity and interference rejection characteristics.
The IF stage is equipped with a Local ⇔ DX automatic switching circuit.
This automatic switching circuit automatically selects the mode of the IF circuit (Local ⇔ DX) by electronically detecting the presence or absence of interference with the received radio wave. The circuit operates by driving the Receiving Mode selection circuit by flip-flop with the signal from the interference detection circuit, and driving the IF stage switching transistor switch and DX indicator.
In the Local position, two sets of block ceramic filters newly developed for the T-1 are used. This block ceramic filter suppresses the differential gain deviation of the pass band within ± 0.2 dB. The IF amplifier is equipped with a buffer amplifier to suppress impedance fluctuation, and a 7-stage differential amplifier with a current limiter with excellent limiter effect is used. These configurations provide excellent characteristics while ensuring sufficient selectivity.
In addition, for the DX position, a 4-element low-spurious ceramic filter whose output characteristics are checked by differential gain direct-viewing method is added to the block ceramic filter for the Local position to improve selectivity and cut interference sharply.
The MPX circuit employs a DC-NFB switching circuit, which is based on a high-through-rate DC amplifier, Yamaha's original transistor-based mean-value-demodulation switching circuit, and NFB (negative feedback) as in the case of audio amplifiers.
In order to eliminate the 19 kHz pilot signal that is unnecessary for audio signals, a 19 kHz square wave generated by a PLL is used to reproduce a 19 kHz sine wave with a level that follows the input pilot signal and a phase opposite to the input signal. A tracking-type pilot pure cancel circuit is installed that cancels the pilot signal at the input of the switching circuit.
This circuit automatically follows even if the pilot signal level of each broadcasting station is different, it automatically follows the level of each pilot and cancels it according to the level of each pilot, so there is almost no leakage of pilots.
Since the output from the MPX circuit does not include a 19 kHz signal, the cut-off frequency of the low-pass filter can be raised to 19 kHz or higher, and almost flat frequency characteristics can be obtained up to 18 kHz.
The PLL circuit generates a 38 kHz subcarrier necessary to demodulate a composite signal from a 19 kHz pilot signal. The Anti-interference PLL interference PLL System with a tunable interference removal filter added to the input to reduce subcarrier disturbance caused by stereo audio signals.
An electronic antenna attenuator is used in the AM tuner section to enable wide-band reproduction of AM broadcasting when receiving a high-field station.
In addition, we have adopted Yamaha's unique combination feeding system that uses an FM antenna as an AM antenna.
The signal meter can indicate an input level of 3 μ V to 1 mV by means of an interference detection filter and AGC amplifier, and the signal meter can indicate multipath or fading as a decrease in indication value or wamble by means of Yamaha's original interference detection circuit without saturation up to a strong input.
Equipped with an Optimum Tuning System (OTS) mechanism.
In the OTS mechanism, the AFC is turned OFF during tuning, and after tuning, the frequency from the station is automatically locked to the correct tuning point, and the dial indicator becomes bright when tuning to the station during tuning and functions as a station indicator.
It is equipped with a 2-stage symmetrical gate muting circuit, an FM blend circuit to reduce noise in stereo reception of weak electric field, and a REC CAL circuit.
Equipped with two output terminals, fixed and variable.
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Model Rating
| Type | AM/FM stereo tuner | ||||||
| FM Tuner Section | |||||||
| FM practical sensitivity (IHF, mono, 300 Ω) | 300 Ω : 1.7 μ V (9.8 dBf) 75 Ω : 0.85 μ V (9.8 dBf) |
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| 50 dBSN sensitivity | Mono : 3 μ V (14.8 dBf) Stereo : 35 μ V (36 dBf) |
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| Image interference ratio (84 MHz) | 95dB | ||||||
| IF Interference Ratio (84 MHz) | 100dB | ||||||
| Spurious interference ratio (84 MHz) | 100dB | ||||||
| AM suppression ratio | 65dB | ||||||
| Capture ratio | 1.0dB | ||||||
| Effective selectivity (IHF) | Local:55dB DX:92dB |
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| Signal-to-noise ratio | mono:86dB stereo:84dB |
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| Total harmonic distortion factor |
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| IM (Intermodulation) Distortion Factor (IHF) |
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| Stereo separation |
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| Frequency characteristic | 50 Hz to 10 kHz ± 0.3 dB 30 Hz to 15 kHz ± 0.5 dB 10 hz ~ 18 khz + 0.5 -3.0 db |
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| Subcarrier suppression ratio | 70dB | ||||||
| Muting level | DX : 5 μ V (19.2 dBf) | ||||||
| AUTO DX operating level | DXMODE automatic switching at interference level of about -50dB in stereo | ||||||
| <AM Tuner Section> | |||||||
| Practical sensitivity (IHF) | 15 μ V | ||||||
| Selectivity (1000 kHz ± 10 kHz) | 30dB | ||||||
| Signal-to-noise ratio (80dB/m) | 50dB | ||||||
| Image interference ratio (1000 kHz) | 70dB | ||||||
| IF Disturbance Ratio (1000 kHz) | 70dB | ||||||
| Spurious interference ratio (1000 kHz) | 70dB | ||||||
| Total harmonic distortion factor | 0.4% | ||||||
| <Audio section> | |||||||
| Output Level / Impedance |
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| Accessory function | Recording calibrator FM Blend Switch, FM Muting & OTS Interlocking Switch FM IF band selector switch (AUTO DX-Normal) Signal Strength/Quality Meter FM Tuning ind(Full - Harf Bright) |
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| <General> | |||||||
| Semiconductor used | Transistor x60 ICx5 FETx1 Diode x17 Two Zener Diodes LEDx2 Ceramic Filter FM2 + Ceramic Block Filter Unit 2/AM1 |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||||||
| Rated power consumption | 11W | ||||||
| External dimensions | Width 435x Height 97x Depth 376 mm | ||||||
| Weight | 5.7kg | ||||||