SANSUI TU-7900

Commentary

FM/AM tuner developed with the theme of high-fidelity FM stereo playback.

The RF stage of the front end section uses a dual-gate MOS-type FET with excellent high-frequency characteristics and low noise. It is combined with a frequency-straight-line-type four variable capacitor with high tuning accuracy and precision finish, so that it has a sufficient ability to eliminate interfering signals.

The IF section uses three dedicated ICs with high gain and excellent limiter characteristics, two 4-element phase linear ceramic filters, two 2-element ceramic filters, etc. This improves the contradictory relationship between selectivity and phase characteristics, and provides a circuit configuration with excellent 2-signal selectivity characteristics and excellent basic characteristics.
The detector circuit uses a ratio detector with good linearity and wide bandwidth.

In the MPX section, PLL system using IC is adopted, and excellent separation characteristics and low distortion factor are obtained.

The AM tuner is designed with high sensitivity by adding one stage RF1 in addition to high-integration ICs. In particular, by using Yaman type 2-element ceramic filters and ICs in the IF section, the circuit has less distortion.
In addition, a whistle filter circuit is installed to prevent beat sound that occurs at night, etc., to improve the sound quality of AM broadcasting.

A well-regulated power transformer is used for the power supply.
In addition, a stabilized power supply by a constant voltage power supply circuit is supplied to all stages, and each block stage realizes highly stable operation.

Equipped with an FM MPX noise canceler, it can cut high-frequency noise generated during FM stereo reception.
The TU-7900 is designed to automatically cut out noise. It automatically operates when FM stereo reception is accompanied by weak radio waves and noise.

Equipped with FM muting circuit.

Equipped with two FM antenna input terminals.

Equipped with an FM antenna attenuator switch, it can receive FM broadcasts at the optimum input level according to the level of strong or weak radio waves.

Equipped with an output volume, the output level can be adjusted.
An output terminal for recording is also provided.

It is equipped with a multi-path observation terminal, and the best FM reception is possible by adjusting the direction of the FM antenna while observing waveform by connecting an oscilloscope.
In addition, the TU-7900 has a built-in multi-path detection circuit and can monitor multi-path conditions with a signal meter.

Ferrite bar antenna is mounted.

The front panel uses an anodized black panel that brings out the hairline.

Model Rating

Type	FM/AM Tuner
FM Tuner Section
Practical sensitivity (IHF)	1.7 μ V/9.8 dBf (new IHF) (Maximum Allowable Input 125 dB or More)
S/N50dB sensitivity	Mono : 3 μ V/15dBf (new IHF) Stereo : 32 μ V/35dBf (new IHF)
Total harmonic distortion factor	Mono : 0.25% or less (1 kHz) Stereo : 0.35% or less (1 kHz)
Signal-to-noise ratio	Mono : 75 dB or higher Stereo : 65 dB or more
Effective selectivity	85 dB or More (± 400 kHz)
Capture ratio	1.5 dB or less
AM suppression ratio	55 dB or more
Image interference ratio (IHF)	70 dB or More (83 MHz)
IF disturbance ratio (IHF)	95 dB or More (83 MHz)
Spurious interference ratio (IHF)	85 dB or More (83 MHz)
Stereo Separation (IHF)	30 dB or More (100 Hz) 40 dB or More (1 kHz) 30 dB or More (10 kHz)
Frequency Response (IHF)	30 Hz ~ 15 kHz + 0.5 -2.0 dB
<AM Tuner Section>
Sensitivity (bar antenna)	50dB/m(1,000Hz)
Selectivity	30 dB or More (1,000 Hz ± 10 kHz)
Image interference ratio	30dB/m or more (1,000 Hz)
IF Rejection	30dB/m or more (1,000 Hz)
<General>
Output Voltage (FM100% Modulation)	Variable Output : 0 ~ 775 mV Recording output : 400 mV
Power consumption	18W
External dimensions	Width 430x Height 132x Depth 243 mm
Weight	6.6kg