ONKYO Integra T-425
¥ 39,800 (around 1981)
Commentary
FM/AM stereo tuner that adopts quartz synthesizer system.
This is a synthesizer tuner that electronically synthesizes local frequencies using a PLL (Phase Locked Loop) controlled by a microcomputer.
The frequency is digitally determined at 100 kHz intervals, and the reference frequency of the PLL is derived from an accurate crystal oscillator. This eliminates the loss of tuning due to changes in temperature and humidity, as well as the degradation of sound quality caused by this.
Built-in 12-station preset memories that store up to 6 FM/AM stations each.
The memory does not disappear even if the power switch is turned off or the power cord is unplugged.
You can choose between auto-scan and manual scan by changing how you press the tuning switch.
In the manual mode, the frequency changes in increments of 0.1 MHz with one push of the switch. In the automatic mode, the frequency changes automatically when the switch is held down. The channel selection is completed by releasing the switch at the desired station while watching the digital frequency display and signal indicator.
In the front-end section, a dual-gate MOS FET with low noise figure and wide dynamic range is adopted in the RF stage.
In addition to improving high sensitivity and interference rejection performance, we have also succeeded in eliminating intermodulation interference and reception interference caused by two adjacent high-level stations.
The IF section that amplifies the intermediate frequency uses a wide-band linear phase filter that is strictly selected by the differential gain direct-viewing method. The IF amplifier uses a high-performance differential IC to obtain a sufficient limiter effect.
In addition, the detector also achieves wide-band linear characteristics by the differential gain direct-viewing method.
The MPX section, which separates audio signals into left and right audio signals, uses a highly stable PLL IC.
In addition, the distortion is thoroughly reduced by adding a strengthening filter and NFB.
The AM section is equipped with an AM-only loop antenna that is resistant to external noise, and uses an AM-only IC that is completely independent of the FM section from the RF stage to the audio section.
With a built-in three step delayed type AGC, two steps to the RF amplifier and one step to the IF amplifier, it maintains a low distortion factor against strong input, and prevents beat disturbance and shock sound during tuning.
It is equipped with noise reduction that automatically prevents S/N degradation by changing the high-frequency blending amount of L/R according to the input level in order to respond to weak radio waves of the desired station.
When the input level is high, the circuit is automatically disconnected.
Model Rating
Type | Quartz digital synthesizer system FM/AM tuner | ||||||
FM Tuner Section | |||||||
Receiving frequency | 76.1 mhz to 89.9 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) | 80dB | ||||||
Image Interference Ratio (83 mhz) | 50dB | ||||||
IF Interference Ratio (83 MHz) | 90dB | ||||||
Signal-to-noise ratio | mono:76dB stereo:72dB |
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Spurious interference ratio | 75dB | ||||||
2-signal selectivity (± 400 kHz detuning) | 60dB | ||||||
AM suppression ratio | 60dB | ||||||
Capture ratio | 1.0dB | ||||||
Distortion factor |
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Frequency characteristic | 20 Hz ~ 15000 Hz + 0 -1dB | ||||||
Antenna impedance | 75 Ω | ||||||
Stereo separation |
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Carrier leak | -50dB | ||||||
Output Voltage / Impedance | Fixed Output : 500mV/1.6k Ω | ||||||
<AM Tuner Section> | |||||||
Practical sensitivity | 200 μ V/m (bar antenna) | ||||||
Image interference ratio / IF interference ratio | 50dB/36dB(999kHz) | ||||||
Two signal selectivity | 35dB | ||||||
Signal-to-noise ratio | 50dB | ||||||
Distortion factor | 0.3% | ||||||
Output voltage | Recorded output : 150 mV | ||||||
<General> | |||||||
Pwer | 100 VAC, 50/60Hz | ||||||
Power consumption | 15W (Electrical Appliance and Material Control Law Standard) | ||||||
External dimensions | Width 435x Height 66x Depth 278 mm | ||||||
Weight | 3.4kg |