ONKYO Integra T-427
¥ 49,800 (around September 1981)
Commentary
FM/AM tuner adopting the newly developed FM feedback system.
In the FM feedback system, part of the output signal of the detector is fed back to the local transmitter through the FM servo circuit, and the local transmitter signal is modulated by the low distortion circuit built into the local transmitter. The modulated local transmitter signal is mixed with the input signal by a mixer and an IF signal is extracted.
Therefore, the FM feedback method has the same effect as doubling the bandwidth of the IF circuit and allows only the part of the IF circuit with the best phase characteristics to pass through.
As a result, the dynamic range of the IF circuit is expanded, and a low distortion factor can be maintained even in the wide IF signal band accompanied by large input in overmodulation.
In addition, since it has the NFB effect, linearity in the IF and detection section is greatly improved, and distortion can be reduced.
Other features include improved separation at the MPX by clearing the signal, enhanced effect of the servo lock system by widening the IF band, and improved tuning accuracy.
Even if a slight phase shift occurs in the detector output signal, the FM servo does not work.
Therefore, since it is necessary to obtain excellent phase characteristics, the IF linear phase filter and wideband ultralinear detector are strictly selected and adopted.
In addition, it is equipped with 2-stage switching of IF bandwidth (low distortion rate WIDE, high selectivity NARROW), and FM feedback is operated only when WIDE.
The front-end consists of a single and double tuned RF amplifier using a dual-gate MOS FET. The mixer is also a double-balanced type with a carefully selected dual-gate MOS FETx2. The output from the station is input to the mixer through an FET buffer to expand the dynamic range at strong input.
Servo lock system is adopted for the lock mechanism.
The MPX section, which separates the L/R audio signal, uses a highly stable AF amplifier built-in, PLL and IC.
In addition, in order to suppress the generation of slight distortion here, we have added a strengthening filter to the PLL / IC to make the distortion factor as a whole MPX diameter low.
The AM section is equipped with a touch sensor servo lock that emphasizes sound quality and pursues comfortable channel selection and perfect tuning.
In addition, a 4-element ladder filter and two impedance matching transformers are employed in the IF stage, which is the heart of sound, in order to expand frequency characteristics and reduce spurious interference.
The IF bandwidth can be switched to two levels : the wide-band WIDE position and the narrow position, which cuts out external interference when reception conditions are poor.
In addition, an AM loop antenna that is resistant to external noise such as fluorescent light noise is used, and a low-noise FET is used at the input stage to increase the selectivity and suppress adjacent station interference with strong input.
Equipped with AF amplifier with wide dynamic range.
440 Hz air check calibrator.
Automatic noise reduction
Equipped with a deviation meter that shows the degree of modulation.
Model Rating
Type | FM feedback system / servo lock FM/AM tuner | ||||||
FM Tuner Section | |||||||
Receiving frequency | 76 MHz to 90 MHz | ||||||
Practical Sensitivity (75 Ω / IHF) | 0.9 μ V/10.3 dBf | ||||||
S/N50dB sensitivity (75 Ω / IHF) | 2.0 μ V/17.3 dBf | ||||||
Intermodulation interference ratio (± 2.5 MHz) | 95dB | ||||||
Image Interference Ratio (83 mhz) | 90dB | ||||||
IF Interference Ratio (83 MHz) | 108dB | ||||||
Signal-to-noise ratio | mono:84dB stereo:80dB |
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Spurious interference ratio | 105dB | ||||||
2-signal selectivity (± 400 kHz detuning) | IF Wide:40dB IF Narrow:85dB |
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AM suppression ratio | IF Wide:62dB IF Narrow:50dB |
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Capture ratio | IF Wide:1.0dB IF Narrow:2.0dB |
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Distortion factor |
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Frequency characteristic | 20 Hz ~ 15000 Hz + 0.2 -0.8 dB | ||||||
Antenna impedance | 75 Ω | ||||||
Stereo separation |
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Carrier leak | -65dB | ||||||
Output Voltage / Impedance | Variable Output : 0 ~ 800mV/3.3k Ω Fixed Output : 450mV/5.6k Ω |
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<AM Tuner Section> | |||||||
Practical sensitivity | 200 μ V/m (bar antenna) | ||||||
Image interference ratio / IF interference ratio | 57dB/42dB(1MHz) | ||||||
Two signal selectivity | IF Wide:20dB IF Narrow:45dB |
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Signal-to-noise ratio | 60dB | ||||||
Distortion factor | IF Wide:0.3% IF Narrow:0.5% |
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Output voltage | Variable Output : 0 ~ 260 mV Recorded output : 150 mV |
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<General> | |||||||
Pwer | 100 VAC, 50/60Hz | ||||||
Power consumption (Electrical Appliance and Material Control Law standard) | 27W | ||||||
External dimensions | Width 435x Height 99x Depth 393 mm | ||||||
Weight | 6.5kg |