Audio Database

Image of the Integra T-406
Commentary

AM/FM stereo tuner equipped with servo lock

The servo lock system of the T-406 detects the difference between the best sound quality point of the minimum distortion and fine separation of the detector and the actual passing signal. A high-gain operational amplifier IC is used to feed back to the local oscillator and fix the local frequency.
At this time, the tuning frequency accuracy is within ± 5 khz of the sound quality best point, and low distortion rate reception is maintained, so that there is no concern that the frequency drift during reception deteriorates the music and loses the clearness of the music.

When the tuning point is within ± 50 kHz of the tuning point, the locked indicator (red) glows to indicate that it is within the locked range. When the tuning position is released, the optimum tuning point is immediately locked and the tuning indicator (green) indicates that the tuning is complete.
In the case of a re-tuning station, when the tuning part is touched, the lock mechanism is released immediately and the tuning state returns to manual tuning. As a result, the delicate complication of center tuning, which is inherent in continuous frequency tuners, is eliminated, and quick and accurate tuning is realized.

Equipped with an excellent lock mechanism, it eliminates the fear of mistuning = sound quality degradation, and always enables good low-distortion recording.

Equipped with a deviation meter that displays the modulation level.
This is a third meter that is equipped to ensure excellent sound quality. It shows the degree of modulation of FM broadcasting. For example, music broadcasting with a wide dynamic range such as 200% modulation has an excess input of + 12 dB over 50% modulation. This meter allows you to take into account the degree of modulation of more dynamic music when setting the recording level of your tape deck.

Equipped with air check and calibrator.
Equipped with an air check calibrator that emits 50% modulation and 440 Hz continuous sound. By setting the appropriate recording level on the tape deck, it is useful for low distortion rate recording with wide dynamic range.

With multi-path output terminal. Can be viewed directly.
Equipped with a multipath output terminal that detects multipath linearly up to a strong input of 70 dB, it is useful for good antenna setting when used in combination with an oscilloscope.
Even if you do not have an oscilloscope, you can connect an amplifier to the multi-path V terminal and check only the distortion component with your ears.

In addition to the variable output terminal for normal amplifier connection, there is also a dedicated output terminal for recording, so that you can record directly to the deck.

A dual-gate MOS-FET known for its low noise figure and wide dynamic range is put into the RF stage, and it is a front-end using a frequency linear type 4 variable capacitor.
In addition to achieving both high sensitivity and excellent interference rejection performance, we have achieved results in eliminating cross-modulation interference, which was often overlooked in the past, and reception interference (intermodulation interference) caused by two adjacent high-level stations.
On the other hand, the effect of temperature and humidity drift is suppressed even in the local station, and combined with the adoption of the servo lock, it demonstrates its power in maintaining the best sound quality with minimum distortion and maximum separation.

The IF section, which amplifies the accurate intermediate frequency (IF) obtained by the front-end mixer, uses a wide-band linear phase filter that is strictly selected by differential gain direct-viewing method. The IF amplifier uses a high-performance differential IC to obtain a sufficient limiter effect.
In addition, the differential gain direct-viewing method is used to obtain wide-band linear characteristics for the detector, which contributes to improving sound quality.

The MPX section (stereo demodulation section), which separates the composite signal obtained from the detector into left and right audio signals, uses a high-stability built-in AF amplifier, new PLL and IC to obtain a stereo signal with a separation of 50 dB (1 kHz).
In order to suppress the generation of distortion, a strengthening filter is added to the stable PLL / IC, and the distortion factor of the MPX system as a whole is thoroughly reduced. This has achieved significant results in improving the sound quality as a whole.

As a countermeasure against overmodulation in FM broadcasting, we adopted an AF amplifier with a large dynamic margin in addition to the IF part and low-distortion MPX part of a wide-band linear phase filter, and achieved a low distortion rate of 0.15% or less at 150% modulation and 0.3% or less at 200% modulation (ST ・ 400 Hz).

A long scale dial with a travel length of 250 mm and a tuning knob with a large flywheel for smooth movement, etc. provide an excellent operational feeling.
In addition, the AM receiver uses a highly sensitive double varicon and a highly selective IF triple tune filter to improve sound quality.

Model Rating
Type Servo lock type AM/FM stereo tuner
FM Tuner Section
Receiving frequency 76 MHz to 90 MHz
Practical sensitivity 1.8 μ V (IHF, 300 Ω)
10.3 dBf (new IHF)
S/N50dB sensitivity 3.0 μ V (IHF)
14.8 dBf (new IHF)
Image interference ratio 80dB(83MHz)
IF interference ratio 95dB(83MHz)
Signal-to-noise ratio mono:77dB
stereo:73dB
Spurious interference ratio 90dB
2-signal selectivity (± 400 kHz detuning) 60dB
AM suppression ratio 53dB
Capture ratio 1.0dB
Distortion factor
Mono, 400 Hz : 0.08%
Mono, 50 Hz to 10 kHz : 0.15%
Stereo, 400 Hz : 0.15%
Stereo, 50 Hz to 10 kHz : 0.3%
Frequency characteristic 20 Hz ~ 15000 Hz + 0.5 -1.5 dB
Antenna impedance 75 Ω, 300 Ω
Stereo separation
1kHz: 50dB
100 Hz to 10 kHz : 38dB
Carrier leak -60dB
Output voltage (400 Hz, 100% modulation) Variable Output : 0 mv ~ 1200 mv
Recorded output : 450 mV
Output impedance Variable output : 2.2k Ω at maximum
Recording Output : 3.9k Ω
<AM Tuner Section>
Receiving frequency 535 kHz to 1605 kHz
Practical sensitivity (bar antenna) 150 μ V/m
Image Interference Ratio (1 MHz) 52dB
IF Interference Ratio (1 MHz) 38dB
Signal-to-noise ratio 60dB
Strain Rate (400 Hz) 0.5%
Output Voltage (400 Hz, 30% Modulation) Variable Output : 0 mv ~ 400 mv
Recorded output : 150 mV
<General>
Semiconductor used 4 ic, 19 tr (1 FET), 21 di
Pwer 100 VAC, 50/60Hz
Power consumption (Electrical Appliance and Material Control Law standard) 14W
External dimensions Width 435x Height 108x Depth 386 mm
Weight 6kg