Audio Database

TU-7700
Commentary

The FM/AM tuner was developed with the aim of reproducing high-quality sound while pursuing basic performance such as sensitivity and selectivity as an FM tuner.

The FM front-end uses a low-noise dual-gate MOS type FET for the RF stage, and high sensitivity is obtained by combining it with a precision frequency linear type four variable capacitor.
In addition, a double tuning circuit is constructed to improve the interference rejection characteristics that cause interference.
In addition, it is equipped with an antenna attenuator switch that can receive signals at the optimum input level according to the level of strong or weak radio waves. It can handle various radio wave conditions and receive signals with a sense of security.

The FM IF section uses two newly developed phase linear ceramic filters (four elements), two stage differential amplification with pair transistors, and three dedicated ICs.
In addition, we have improved the SN ratio, capture ratio, AM suppression and other characteristics by using a linear and wide-band ratio-detection circuit in the discriminator.

A phase-linear ceramic filter is used in the filter element that influences the selectivity of the IF section.

The FM MPX section uses a high-reliability dedicated IC that does not degrade over time or due to ambient temperature, resulting in high separation.

The AM tuner section features a highly sensitive ferrite bar antenna and a dedicated IC2-element Yaman type ceramic filter, resulting in a more complete circuit structure.

The FM muting circuit is a discriminator detection type that employs a highly reliable IC.
It is a circuit method that detects the deviation from the tuning frequency separately from the signal level, and does not produce sound until the distortion rate becomes less than a certain value.

In addition to the multi-path observation terminal for the oscilloscope, a multi-path detection circuit is installed, and the best radio wave direction can be determined by the signal meter by switching the meter selector.

Equipped with a noise canceler switch, it improves the SN ratio without losing the musical quality when receiving FM stereo in a weak electric field.

A power transformer with good regulation is used for the power supply section, and a stabilized power supply by a constant voltage circuit is supplied to all block stages.

Both balanced and unbalanced coaxial terminals can be used for the FM antenna input terminal.

Uses a 2-meter system consisting of a signal meter and a tuning meter.

The output terminal has two circuits, one for amplifier and the other for recording.
The level of the amplifier output terminal can be adjusted.

Equipped with large grounding terminal and spare AC outlet.

Uses die-cast side panels.

It was equipped with a 4 ch adapter for FM4ch discrete broadcasting.

Model Rating
Type FM/AM Tuner
FM Tuner Section
Sensitivity (IHF) 1.8 μ V
Total harmonic distortion factor Mono : not more than 0.2%
Stereo : 0.3% or less
Signal-to-noise ratio 75 dB or more
Selectivity 80 dB or more
Capture Ratio (IHF) 1.5dB
Image Frequency Rejection 75 dB or More (83 MHz)
IF Rejection 90 dB or more (83 MHz)
Spurious response rejection 80 dB or More (83 MHz)
Stereo separation 40 dB or More (1 kHz)
Frequency characteristic 20 Hz to 15 kHz
Antenna input impedance 300 Ω (Balanced Type)
75 Ω (Unbalanced Type)
<AM Tuner Section>
Sensitivity (bar antenna) 50dB/m(1MHz)
Selectivity 30 dB or More (1 MHz ± 10 kHz)
Image frequency rejection 80 dB or More (1 MHz)
IF Rejection 80 dB or More (1 MHz)
<General>
Output voltage 0 V ~ 0.775 V (FM100% MOD. Variable)
Recording output voltage 0.4V
Rated power consumption 9W
External dimensions Width 434x Height 130x Depth 243 mm
Weight 6.9kg