Audio Database

Image of Integra T-429R
Commentary

FM 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.

The front-end consists of a direct-input triple-tuned frequency linear 7-train varicon and a wide-dynamic-range dual-gate MOS FETx2 double-balanced mixer. The output from the station is fed into the mixer through a three terminal MOS FET tuned buffer.
In addition, the antenna input stage switches between Booster OUT (direct) and IN, so that the optimum sensitivity can be selected according to the receiving condition (difference in electric field strength).
Boost OUT (direct) is a position that can show interference rejection performance in a strong electric field region. After the input triple tune, it enters directly into the mixer without passing through RF (high-frequency amplification). This ensures a sufficient dynamic range, eliminates interference such as intermodulation, and enables stable and clear reception.
The Booster IN is a position for low-power regions. Before the triple tune, RF amplification (input single tuning) by a MOS FET is added. This enables a high sensitivity of 0.9 μ V to receive weak radio waves over a long distance.

The station signal part uses a dedicated independent power supply separated from the audio part.
In addition, it is equipped with a mechanical stabilizer that shuts out vibrations from the speakers, thereby thoroughly preventing adverse effects caused by electrical and mechanical interference.

The MPX uses a high-speed response C-MOS analog switching element and an active filter and pilot canceler to cut the sub-carrier component after L/R separation to prevent the sound quality degradation caused by magnetostriction of the LC low-pass filter.

The audio section consists of a servo operational amplifier, and a low-noise operational amplifier IC is used for the servo amplifier IC, which not only improves music reproduction but also ensures a wide range of frequency characteristics up to 2 hz.

A sensor circuit is used to cut low-frequency pop noise only when the tuning knob is touched.

It is equipped with a multi-path detection meter that is useful for good antenna installation.
It also functions as a deviation meter to indicate the degree of modulation by switching the switch, making it easier to set the level during recording.

Model Rating
Type FM Feedback System / Super Servo 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 : 1.7 μ V/15.8 dBf
Intermodulation interference ratio
(± 1 mhz / ± 2.5 mhz)
RF Booster out:100dB/105dB
RF Booster in:90dB/100dB
Image Interference Ratio (83 mhz) RF Booster out:100dB
RF Booster in:120dB
IF Interference Ratio (83 MHz) RF Booster out:110dB
RF Booster in:120dB
Signal-to-noise ratio mono:90dB
stereo:86dB
Spurious interference ratio RF Booster out:120dB
RF Booster in:120dB
2-signal selectivity (± 400 kHz detuning) IF Wide:45dB
IF Narrow:85dB
AM suppression ratio IF Wide:65dB
IF Narrow:55dB
Capture ratio IF Wide:1.0dB
IF Narrow:2.0dB
Distortion factor
Mono, 50 Hz to 10 kHz : 0.004%(IF Wide)
0.01%(IF Narrow)
Stereo, 400 Hz : 0.008%(IF Wide)
0.3%(IF Narrow)
Stereo, 50 Hz to 10 kHz : 0.03%(IF Wide)
0.4%(IF Narrow)
Frequency characteristic 2 Hz ~ 15000 Hz + 0.2 -0.8 dB
Antenna impedance 75 Ω, 300 Ω
Stereo separation
1kHz: 60dB(IF Wide)
45dB(IF Narrow)
100 Hz to 10 kHz : 50dB(IF Wide)
40dB(IF Narrow)
Carrier leak -65dB
Output Voltage / Impedance Variable Output : 0 ~ 1200mV/100 Ω
Fixed Output : 500mV/3.3k Ω
<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 5.6kg
Sold Separately Sidewood CW-9 (¥ 5,000)