TRIO KT-7700

Commentary

An FM stereo tuner developed by comprehensively pursuing all aspects.

The front end uses a single-double-triple-tune configuration, a precision 7-series varicon with reduced tracking error and gang error, and a small-capacity load DD-MOS type FET to achieve excellent interference rejection performance while maintaining low distortion characteristics.

The RF stage is a 2-stage amplifier, and the amplifier element uses a DD-MOS type (double diffused dual-gate MOS type) FET, which is an improved version of the dual-gate MOS-FET. The high-frequency characteristics of this FET have been greatly improved by diffusing the conventional MOS-FET once again. In addition, the DD-MOS-FET has superior spurious characteristics and intermodulation characteristics, superior ultra-high-frequency characteristics, superior sensitivity because the noise figure is small, and stable operation can be obtained because the feedback capacity is small.

Dual gate MOS-FET is used for the mixer stage.

A buffer circuit is used for the station generator to enhance intermodulation and AM suppression.

The IF stage is equipped with 2-stage band switching, which achieves both high selectivity characteristics and low distortion rate.
The demodulation circuit uses a multi プリケーティブ discriminator system consisting of a Bessel delay device, waveform shaping device and multiplier.

The Narrow band consists of three stages of 4-element phase-linear ceramic filters to achieve high selectivity.

Uses an 8-pole (4-pole 2-stage) LC concentrated filter with excellent group delay characteristics.
In addition, by installing a buffer circuit, deterioration of group delay characteristics due to parameter changes of the amplifying element is suppressed.

The loop response of the PLL is automatically switched.
The PLL circuit detects the pilot signal from the composite signal. If the loop response of the PLL is fast, the filter action is weakened, and the main signal is mixed into the subcarrier, causing a kind of intermodulation. Therefore, with the loop response automatic switching installed in the KT-7700, the PLL is locked as soon as the stereo indicator lamp lights up, and the input level is lowered to slow the loop response and strengthen the filter action. This greatly reduces the high-frequency distortion during stereo reception.

A FET is used in the MPX switching circuit to realize a low distortion factor.

The audio amplifier uses a differential direct-coupled ± 2 power source operational amplifier.
In addition, by driving all audio signal systems after the discri with ± 2 power supply, deterioration of distortion hardly occurs even at 300% overmodulation.

TRIO's unique FET switching system D. S. D. C is adopted.
In this method, the left and right separation is adjusted independently.

A 7-element Norton conversion filter is used for the low-pass filter with an emphasis on the phase characteristics of the audio section.

Equipped with de-emphasis circuit of high-precision design.
Resistors and capacitors are strictly controlled and selected high-precision elements are used.

It is a local oscillation built-in type varicon which integrates the varicon and the local oscillator.
In this varicon, a wing for fine tuning of the varicon has been added to keep the rotation angle and local frequency within ± 60 khz.
In addition, we prevent adverse effects due to moisture absorption of the printed circuit board by using three dimensional wiring for the station and eliminating the printed circuit board.

The air-trimmer used for the oscillator circuit is also highly stable, providing a tuner that is resistant to environmental changes.

Metal glaze semi-fixed volume and metal film resistance are adopted, and temperature and humidity changes of the separation adjustment part and PLL-VCO adjustment part are suppressed.

There was a carrying handle as an option sold separately.

Model Rating

Type	FM stereo tuner
Receiving frequency	76 MHz to 90 MHz
Antenna impedance	300 Ω equilibrium 75 Ω unbalance
Sensitivity (IHF)	1.5 μ V (300 Ω) 0.8 μ V (75 Ω)
SN ratio 50 dB quieting sensitivity	Mono : 2.8 μ V Stereo : 30 μ V
Distortion factor (100% modulation)	Wide mono:0.08%(1kHz) 0.1% (50 Hz to 10 kHz) 0.15%(15kHz) stereo:0.1%(1kHz) 0.15% (50 Hz to 10 kHz) 0.4%(15kHz) Narrow mono:0.15%(1kHz) stereo:0.4%(1kHz)
Signal-to-noise ratio (100% modulation, 1 mv input)	mono:78dB stereo:75dB
Image ratio	120dB
Selectivity (IHF)	Narrow 110dB(400kHz) 60dB(300kHz) Wide 35dB(400kHz)
IF interference ratio	120dB
Harmonics spurious response	120dB
AM suppression ratio	65dB
Capture ratio	Wide:1.0dB Narrow:1.5dB
Stereo separation	Wide 50dB(1kHz) 45 dB (50 Hz to 10 kHz) 40dB(15kHz) Narrow 45dB(1kHz)
Carrier leakage	70dB
Frequency characteristic	50 Hz to 10 kHz ± 0.2 dB 30 Hz to 15 kHz + 0.2 -1.2 dB
Output Level / Impedance	FM (400 Hz, 100% modulation) Variable : 0 ~ 1.5V/1.2k Ω Fixed : 0.75V/1.0k Ω FM det out:0.3V Multipath output : 0.3 V (H), 0.1 V (V)
Power supply voltage	100 VAC, 50Hz/60Hz
Rated power consumption (Electrical Appliance and Material Control Law)	22W
External dimensions	Width 380x Height 149x Depth 376 mm
Weight	8.5kg
Sold Separately	Carrying Handle D-7 (1 set, ¥ 3,000)