Audio Database

TU-720
Commentary

FM/AM tuners with the latest devices, technologies and designs to improve sound quality and operability.

The front-end section uses an FET with excellent high-frequency and noise characteristics in the first stage, and a high-precision 3-row varicon.
In addition, the intermediate frequency amplifier stage (IF stage) has a three stage configuration of linear phase ceramic filter that achieves both low distortion factor and high selectivity, and realizes low distortion.

The detector uses newly developed Quadrature detection ICs to improve the linearity of the phase characteristics, reduce distortion and improve the S/N ratio.
The newly developed PLL-MPX IC is used in the MPX section, and the ripple filter circuit dedicated to the MPX section reduces noise components caused by power supply ripple and improves various characteristics.

In order to suppress degradation of the music signal, a line amplifier is built into the IC, and the coupling and condenser between the MPX section and the audio amplifier are removed to create a DC configuration. This reduces the influence on frequency characteristics, distortion factor, S/N, etc.

A servo lock circuit is built in to ensure stable oscillation without the local oscillation frequency being affected by ambient temperature change.
After tuning by the tuning mechanism using LED, the servo lock mechanism is operated to prevent tuning deviation and to enable stable reception with less distortion.

The tuning display at the time of FM reception uses three LEDs to indicate the direction of frequency shift (indicated by the red LED) and just tuning (indicated by the green LED).
The signal level of the antenna input is indicated by 10 LEDs for both FM and AM. The number of LEDs that turn on varies depending on the strength of the radio wave.

The AM tuner consists of an IF stage consisting of a double varicon, two stages of 3-terminal high-selectivity ceramic filters, and a coil. This ensures stable sound quality while eliminating 9 kHz beat interference.
In addition, the newly developed low-impedance loop type antenna, which is resistant to various types of noise in the air, has been adopted for high sensitivity and high S/N. The antenna is detachable from the back panel.

Built-in oscillator for recording level check convenient for air check.

Each function of FM/AM/Rec. Cal can be switched electronically.

It is equipped with a muting circuit that removes noise when the power supply is on / off and noise between stations.

Model Rating
Type AM/FM Tuner
FM Tuner Section
Receiving frequency 76 MHz to 90 MHz
Antenna terminal 75 Ω, 300 Ω (Terminal Type)
Practical sensitivity 0.85 μ V/9.8 dBf
S/N50dB sensitivity Stereo : 15 μ V/34.7 dBf
Mono : 1.7 μ V/15.6 dBf
(μ V at 75 Ω, 0 dBf at 10-15W (new IHF standard)
Image interference ratio 56dB
IF interference ratio 95dB(83MHz)
Spurious response 80dB(83MHz)
AM suppression ratio (IHF) 55dB
Effective selectivity 65 dB (± 400 kHz)
Capture ratio 1.0dB
Frequency characteristic 20 Hz to 15 kHz + 0.2 -1.5 dB
Signal-to-noise ratio stereo:84dB
mono:86dB
Total harmonic distortion rate (1 kHz) Stereo : 0.06% at 90% modulation
Mono : 0.04% at 100% modulation
Stereo separation 55dB(1kHz)
Muting action level 22dB
Output level 0.6 v (at 100% modulation)
<AM Tuner Section>
Receiving frequency 525 to 1605 kHz
Antenna Terminal type with loop antenna
Practical Sensitivity (S/N20dB) 15 μ V
Selectivity 36 dB (± 9 kHz)
Signal-to-noise ratio 55dB
Total harmonic distortion factor 0.4%(1kHz)
Output level 0.2 V at 30% modulation
Level check Signal
Frequency 440 Hz sine wave
Output level 0.3 v (at 50% modulation)
<General>
Pwer 100 VAC, 50Hz/60Hz
Power consumption 11W
External dimensions (including knob, leg and terminal) Width 434x Height 66x Depth 308 mm
Weight 3.8kg