Audio Database

TU-666
Commentary

This FM/AM tuner uses new FM technology to improve practical performance.

The FM front-end has improved intermodulation characteristics, image ratio, S/N ratio, and distortion by using FET and frequency linear type 3-row varicon.

The IF stage has excellent IF characteristics with 4-stage IF and 3-stage limiter using IC.
As a result, the effective selectivity of the IF stage has been dramatically improved to 45 dB. Along with the improvement of the capture ratio, the distortion factor, separation characteristics, and phase characteristics in the high frequency range at the time of stereo broadcast transmission reception have been improved.
In addition, the AGC eliminates distortion caused by strong input.

The MPX circuit has a highly reliable circuit configuration with an SCA filter and an LC-type carrier leak filter with sharp cutoff characteristics.
This reduces beat interference and intermodulation distortion.

By adopting a new method instead of the conventional high-cut filter, we have succeeded in reproducing frequencies above 10 kHz.

By using a frequency number line type 3-row varicon, the frequency scale is equally spaced from 76 to 90 MHz.
With a round dial, 1 MHz can be divided into four and read every 250 kHz.
In addition, the dial is a fantastic illumination dial made of smoked acrylic, and the pointer is self-written and easy to see.

It is equipped with pure electronic FM stereo / mono switching. In FM AUTO, when FM broadcasting changes from mono to stereo, the electronic switch automatically operates and switches to stereo.
In stereo mode, the stereo indicator lights up.

In addition to the 300 Ω balanced antenna input terminal, a 75 Ω terminal for coaxial cable is mounted.

A muting circuit is adopted in order to eliminate noise entering between stations during channel selection.

The AM section is highly sensitive by using a large ferrite bar antenna and ceramic filter, improving selectivity and Radio noises rejection capability.

The power supplies for the IF stage and the front end of the FM IF are stabilized power supplies with ripple filters. In particular, the front end has succeeded in eliminating the AFC circuit by minimizing local drift.

The output circuit has a semi-fixed output level adjustment so that it can be connected to any amplifier, and can be set to the level corresponding to the program source.

Model Rating
Type FM/AM Tuner
FM Tuner Section
Receiving frequency 76 MHz to 90 MHz
Sensitivity 20 dB quieting : 2 μ V
IHF : 2.5 μ V
Total harmonic distortion factor Not more than 0.8%
Signal-to-noise ratio 65 dB or less
Selectivity 45 dB or more
Capture Ratio (IHF) 3dB
IF Rejection 60 dB or more
Image フレクェンシー Rejection 55 dB or more
Spurious response rejection 60 dB or more
FM stereo / separation 35 dB or More (400 MHz)
Unwanted radiation 34 dB or less
Antenna and input impedance 300 Ω : Balanced
75 Ω : Unbalanced
<AM Tuner Section>
Receiving frequency 535 kHz to 1605 kHz
Sensitivity 150 μ V (1000 kHz, bar antenna)
Image フレクェンシー Rejection 40 dB or More (1000 kHz)
Selectivity 25 dB or More (1000 kHz)
Output 0.7V
<General>
Semiconductor used Transistor : 24
FET:1
IC:1
Diode : 19
Power supply voltage 100 V, 50Hz/60Hz
Power consumption 15W
External dimensions Width 335x Height 127x Depth 278 mm
Weight 5kg