ONKYO Integra T-427

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
Spurious interference ratio	105dB
2-signal selectivity (± 400 kHz detuning)	IF Wide:40dB IF Narrow:85dB
AM suppression ratio	IF Wide:62dB IF Narrow:50dB
Capture ratio	IF Wide:1.0dB IF Narrow:2.0dB
Distortion factor	Mono, 50 Hz to 10 kHz : 0.04%(IF Wide) 0.2%(IF Narrow) Stereo, 400 Hz : 0.03%(IF Wide) 0.4%(IF Narrow) Stereo, 50 Hz to 10 kHz : 0.08%(IF Wide) 0.5%(IF Narrow)
Frequency characteristic	20 Hz ~ 15000 Hz + 0.2 -0.8 dB
Antenna impedance	75 Ω
Stereo separation	1kHz: 57dB(IF Wide) 45dB(IF Narrow) 100 Hz to 10 kHz : 47dB(IF Wide) 40dB(IF Narrow)
Carrier leak	-65dB
Output Voltage / Impedance	Variable Output : 0 ~ 800mV/3.3k Ω Fixed Output : 450mV/5.6k Ω
<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
Signal-to-noise ratio	60dB
Distortion factor	IF Wide:0.3% IF Narrow:0.5%
Output voltage	Variable Output : 0 ~ 260 mV Recorded output : 150 mV
<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