ONKYO Integra T-427R

Commentary

FM/AM stereo tuner using 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 an ultra-low distortion modulation circuit built into the local transmitter. The modulated local transmitter signal is mixed with the input signal by a mixer to extract the IF signal.
NFB (Negative Feedback), an amplifier distortion reduction technology, has been introduced into the IF and detection section of the tuner to improve linearity and reduce distortion. In particular, this FM feedback circuit reduces the distortion of the local frequency modulation circuit to 1/10 of the conventional one, improving the distortion reduction effect.
Also, by applying FM servo feedback, the IF spectrum signal band is greatly compressed. This is equivalent to expanding the bandwidth of the IF circuit. The IF signal band can only pass through the part of the IF circuit that has the best phase characteristics. This allows the wide IF signal band for stereo reception or dynamic live programming (overmodulation) to pass and amplify linearly.
In addition, since the stereo separation signal included in the IF spectrum is also transmitted, the phase shift in the MPX demodulator is suppressed and separation is improved.

Even if there is a slight phase shift in the detected output signal, the FM feedback (servo) does not work, so we pursue excellent phase characteristics. To this end, we carefully select and select an IF linear phase filter and a wideband ultralinear detector.

Equipped with 2-stage switching of IF bandwidth, FM feedback operation can be selected at WIDE time.

For the first time in its class, the front-end is equipped with two levels of sensitivity switching (Boost Out/In). You can choose between Out = Triple and High sensitivity depending on the reception area.
Especially in the Direct position, the input triple tune is followed by direct input to the mixer (MOS FET), and the local output is input to the mixer through the FET buffer to expand the dynamic range at the time of strong input reception.
In areas with weak reception, switching to the high-sensitivity position (Boost-In) adds an RF amplifier and operates to enable high-sensitivity reception.

Equipped with a servo-lock system, the best sound quality is maintained by improving the tuning stability.
When the tuning range is reached, the locked indicator flashes, and as soon as you release the tuning knob, as soon as the tuning knob is released.

A highly stable AF amplifier, PLL and IC are used in the MPX section, which separates audio signals into left and right.
We have also added an enhanced filter to the stable PLL / IC, and have achieved significant improvements in overall sound quality.

It is equipped with a deviation meter that shows the degree of modulation and serves as a guide for setting the FM recording level.

The AM part is equipped with a touch sensor and servo lock, and the IF stage is equipped with a 4-element ladder filter and two impedance matching transformers to expand frequency characteristics and reduce spurious interference.
In addition to the IF bandwidth WIDE position, it also has a narrow position.
In addition, a high-sensitivity AM loop antenna that is resistant to external noise such as fluorescent light noise is used, and the amplitude characteristic of the antenna coil is made steep to increase the selectivity.

There was a real wood side plate (CW-9) sold separately.

Model Rating

Type	FM feedback system / servo lock AM/FM stereo tuner
FM Tuner Section
Receiving frequency	76 MHz to 90 MHz
Practical Sensitivity (75 Ω / IHF)	RF Booster out : 1.75 μ V/16.1 dBf RF Booster in : 0.9 μ V/10.3 dBf
S/N50dB sensitivity (75 Ω / IHF)	RF Booster in : 2.0 μ V/17.3 dBf
Intermodulation interference ratio (± 1 MHz / ± 2.5 MHz)	RF Booster out:90dB/100dB RF Booster in:85dB/95dB
Image Interference Ratio (83 mhz)	RF Booster out:90dB RF Booster in:90dB
IF Interference Ratio (83 MHz)	RF Booster out:100dB RF Booster in:120dB
Signal-to-noise ratio	mono:84dB stereo:80dB
Spurious interference ratio	RF Booster out:110dB RF Booster in:120dB
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 : 0.009%(IF Wide) 0.15%(IF Narrow) Stereo, 400 Hz : 0.02%(IF Wide) 0.4%(IF Narrow) Stereo, 50 Hz to 10 kHz : 0.08%(IF Wide) 0.6%(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 : 500mV/5.6k Ω
<AM Tuner Section>
Practical sensitivity	200 μ V/m (loop 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, 50Hz/60Hz
Power consumption (Electrical Appliance and Material Control Law standard)	27W
External dimensions	Width 435x Height 99x Depth 393 mm
Weight	5.2kg
Sold Separately	Side Plate CW-9 (2 Sheets 1 Set, ¥ 5,000)