YAMAHA T-2
¥ 130,000 (around 1978)
Commentary
FM stereo tuner with RF mode switching circuit.
A frequency number line wide air gap precision 7 series varicon is adopted for the front end. The RF-amplifier is two stage amplification using dual gate MOS FET. The stage between the 1st RF amplifier and the 2nd RF amplifier is double-tuned, and the stage between the 2nd RF amplifier and the mixer is triple-tuned to improve the interference rejection characteristics.
In addition, the front-end operation can be switched by an RF mode switching circuit that can switch the operation of the high-frequency amplifier stage according to the radio wave environment of the receiving station. There are two selectable positions : Hi-Sensitivity, which emphasizes sensitivity, and Hi-Selectivity, which emphasizes interference rejection characteristics.
The IF stage is equipped with a Local ⇔ DX automatic switching function, and automatically selects the IF circuit mode by electronically detecting the presence or absence of interference to the received radio wave.
In the Local position, two sets of block ceramic filters newly developed for the T-2 are used. This block ceramic filter combines CR with the input / output circuit of each filter element in order to correct the dispersion of the conventional ceramic filter, and impedance matching is taken, and the differential gain deviation of the pass band is kept within ± 0.2 dB.
In addition, after setting in the IF circuit, it is again checked and adjusted by the differential gain direct viewing method. The IF amplifier is equipped with a buffer amplifier to suppress impedance fluctuation, and a 7-stage differential amplifier with excellent limiter effect is adopted.
This provides excellent audio characteristics while ensuring sufficient selectivity.
In the DX position, two additional ceramic block filters are added to the block filter for the Local position to obtain high selectivity and sharply cut interference.
The MPX circuit is based on a high-through-rate DC amplifier and employs a DC NFB switching circuit that applies NFB (negative feedback) in the same way as an audio amplifier, in addition to an average demodulation method switching circuit using Yamaha's proprietary transistors, thereby improving audio characteristics.
In order to eliminate the 19 kHz pilot signal that is unnecessary for audio signals, a level-following pilot pure cancel circuit is installed. This circuit uses the 19 kHz square wave generated by the PLL to reproduce the level that followed the input pilot signal and the 19 kHz sine wave that is opposite to the input signal. The pilot signal is cancelled by the input of the switching circuit. This circuit automatically follows the level of each pilot and cancels it according to the level of each pilot, even if the pilot signal level of each broadcasting station differs, so there is almost no pilot leakage.
Since the output from the MPX circuit does not include a 19 kHz signal, it is possible to raise the cutoff frequency of the low-pass filter to 19 kHz or higher, and almost flat characteristics are obtained up to 18 kHz.
The PLL circuit employs the Anti-interference PLL System, which adds a tunable interference removal filter to the input and minimizes subcarrier disturbance caused by stereo music signals.
The sub-carrier is switched with a square wave of duty ratio 1.
It is equipped with a station indicator that digitally displays the frequency of the station when it is tuned to the station during tuning.
(Tuning frequency is always displayed when muting is off.)
It is equipped with an interference detection type signal meter, and it can indicate a wide input level of 3 μ V ~ 1 mV by the interference detection filter and AGC amplifier.
In addition, Yamaha's unique interference detection method supports interference from multipath and fading noise sources as a drop in indication value or wamble without saturation up to strong input.
Equipped with an OTS (Optimum Tuning System) mechanism, the AFC is turned off during tuning, and after tuning, the OTS automatically locks the local frequency to the correct tuning point.
When in sync with the station, the digital station indicator lights up to accurately indicate the frequency of the selected station.
It is equipped with a two stage symmetrical gate muting circuit, an FM blend circuit to reduce noise in stereo reception of weak electric field, and a Rec Cal circuit.
There are two types of output terminals, fixed and variable.
Model Rating
| Type | FM stereo tuner | ||||
| FM practical sensitivity (IHF, 300 Ω) | Mono : 1.5 μ V/8.8 dBf | ||||
| Image interference ratio | 120dB | ||||
| IF interference ratio | 120dB | ||||
| Capture ratio | Local:1.0dB DX:1.5dB |
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| Effective selectivity (IHF) | Local:55dB DX:100dB |
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| Signal-to-noise ratio | mono:88dB stereo:85dB |
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| Total harmonic distortion factor |
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| Stereo separation | Local:55dB DX:35dB |
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| Frequency characteristic | 30 Hz ~ 15 kHz + 0. 3-0. 5 dB | ||||
| Subcarrier suppression ratio | 72dB | ||||
| Accessory circuit | RF Mode switch Auto DX circuit OTS Mode switch Autoblend Rec calibrator Digital station display Multi-path terminal |
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| Power supply voltage | 100 VAC, 50Hz/60Hz | ||||
| Rated power consumption | 18W | ||||
| External dimensions | Width 435x Height 70x Depth 349 mm | ||||
| Weight | 7kg |