What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Sansui TU 3900 (1977)

To many, the ability to send music - even stereo and 4-channel music - through the air via radio beams still has the awesome and mysterious quality of magic about it. Few people specialists really understand how the phenomenon works, but we all enjoy it, none theless. And if the equiment used is truly first class, our enjoyment is increased a thousandfold.

Sansui's widley acclaimed TU series of stereo FM/AM tuner components is engineered and built with extraordinary care to assure first-class performance in any situation. Reception and reproduction of FM stereo and AM broadcasts in even the most remote areas - or in the very heart of station-congested urban areas - is guaranteed by Sansui's original research and development of sensitive and very stable tuner circuits in every TU we make. The TU-3900, which matches the Sansui AU-4900/3900 amplifiers in looks, performance and price range, is by no means an exception to this tradition.

Designed for Functional Versatility

One look and listen to the TU-3900 confirms that it's a first-class tuner in every way. Its easy-to-read slanted tuning dial is FM linear (each 250 Hz section is equidistant from the next) and its twin tuning meters are positioned for accurate use. Note the large tuning knob, smoothly counterbalanced with a flywheel inside. Note, too, the LED illumunators for pinpoint tuning and FM Stereo indication, and the pushbutton FM Muting and FM Antenna Attenuator switches. What's more, the rear panel has facilities for Dolby FM and discrete 4-channel FM adaptor connections and more.

IC-Packed Circuitry with MOSFET's

The TU-3900 has an IC-packed FM frontend with a dual-gated MOS FET transistor and a newly-designed low-noise transistor amplifier for ideal FM reception. Its precision-finished 3-gang variable capacitor helps you tune in your favorite FM station with minimum interference. And the two bi-resonator ceramic filters and monolithic IC limiter in the FM intermediate frequency (IF) stage mean clear and trouble-free FM reception for years.

ICs for MPX Stereo and AM, Too

Integrated circuits have also been applied to the MPX (multiplex) stereo FM demodulator section, FM IF section and AM section, too. LEDs for the red-illuminated dial pointer and the FM Stereo indicator also mean longer, more reliable performance. ANd to assure the stable operation of all circuits, a constant voltage power supply furnishes each with a steady and unchanging flow of power irrespective of fluctuations in AC line voltage.

AM Reception is Better Than EVer

AM broadcasting has come a long way toward reducing noise and improving frequency response lately. Our AM section takes advantage of these improvements by incorporating a high-density monolithic IC a bi-resonator Jaumann ceramic filter, a large, built-in AM bar antenna and other advanced features. Particular attention has been paid to the elimination of AM "whine whistle and boom" and the reduction of adjacent-station interference.

Accurate Twin Tuning Meters

The problem of meters which can be fooled or over-saturated by false radio signals is one which Sansui has taken very definite steps to solve. Ans solved it we have . The twin meters in the TU-3900 are as accurate and linear as any ever developed, while at the same time they are extremely easy to use. The one at the far left of the tuning dial is a signal-strength meter for tuning both FM an AM broadcasts. It is specially damped to indicate when you have selected the tuning position at which the incoming signal is at its maximum strength for clear reception. The next is a center-of-channel meter for FM tuning. When its needle points exctly to the middle of its scale you know that your station is tuned to where noise is at a minimum and stereo separation is ideal.

FM Antenna Attenuator

The FM Antenna Attenuator button on the TU-3900 is a feature you won't find on the average tuner in this price range. When the distance from your listening room to the transmitter is short, use this button to reduce the strength of too-strong signals to avoid overload distortion and to clarify FM sound.

FM Muting

As in most high-quality FM tuners, the TU-3900 features a built-in FM Muting circuit to eliminate inter-station "hiss" noise while you tune from station to station. Unlike many tuners in this price range, however the FM Muting circuit is switched on the front panel to allow you to disconnect it when you wish to tune in faint or distant stations which otherwise might be muted out.

Dolby FM and FM4-Channel Features.

The use of the Dolby System to reduce the noise-level in FM transmissions is gaining in popularity in parts of America and the rest of the world. Special Dolby FM adaptors are required to take advantage of this improvement, and the rear panel of the TU-3900 is especially equipped to accept them. Also on the rear panel is a DET OUT jack to which you may connect an adaptor for the reproduction of discrete 4-channel FM broadcasts when and if such broadcasts and adaptors become commercially available.

Additional Features

The rear panel of the TU-3900 also features an extra AC convenience outlet so that you may, for instance, connect and power a tape deck for tuner-to-deck recording. The built-in AM bar antenna is designed so that external Am antennas are not required inmost cases. FM antenna connections are provided for the 300-ohm and 75-ohm (coaxial) type leads.


FM Section

Tuning Range: 88 to 108 MHz

Sensitivity: 2,0 μV (IHF); 1,1 μV

Total Harmonic Distortion: less than 0,3% (Mono); 0,4% (Stereo)

Signal-to-noise Ratio: better than 70 dB

Selectivity: better than 60 dB

Capture ratio: less than 2,0 dB

Image Frequency Rejection: better than 55 dB at 98 MHz

IF Rejection: better than 80 dB at 98 MHz

Spurious Response Rejection: better tham 70 dB at 98 MHz

Spurious Radiation: less than 34 dB

Stereo Separation: better than 40 dB at 1 kHz

Frequency Response: 30 to 15,000 Hz

Antenna Input Impedance: 300 Ω (balanced); 75 Ω (unbalanced)

FM Antenna Attenuator: -20 dB

AM Section

Tuning Range: 535 to 1,605 kHz

Sensitivity (Bar antenna): 53 dB/m at 1,000 kHz

Selectivity (±10 kHz): better than 30 dB at 1,000 kHz

IF Rejection: better than 80 dB/m at 1,000 kHz

Output Level

Output: 775 mV at FM 100% modulation

Dolby: 250 mV at FM 100% modulation


AC Outlet: unswitched Max. 150 watts

Semiconductors: 13 Transistors; 1 Zener Diode; 1 FET; 3 ICs; 2 LEDs; 6 Diodes

Power requirement: 100, 120, 220, 240 V, 50/60 Hz

Power Consumption Rated: 5 watts

Dimensions (W x H x D): 400 x 120 x 240 mm (15¾ x 4¾ x 9½ inch)

Weight: 5,0 kg (11 lbs) Net

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