DENON TU-520

Commentary

The FM/AM tuner was developed with an emphasis on basic performance by making full use of the latest devices and tuner technology at that time.

In the front end section, an FET with excellent high-frequency and noise characteristics is used in the first stage, and sensitivity and S/N have been improved by the adoption of a 3-row varicon.
We have also improved the image interference rejection capability of neighboring stations.

The IF (intermediate frequency amplification stage) has a three stage configuration of linear phase ceramic filter that achieves both low distortion factor and high selectivity. Combined with newly developed Quadrature detection ICs and PLL-MPX ICs, low distortion factor has been realized.

The newly developed PLL-MPX IC is used in the MPX section, and noise components due to power supply ripple are reduced by a ripple filter circuit exclusive to the MPX section.
In addition, in order to output the music signal obtained by this circuit without degradation as much as possible, a line amplifier is built into the IC and the coupling capacitor between the MPX section and the audio amplifier is removed to make a DC configuration.

A frequency control system (servo lock) is built in so that the local oscillation frequency is not affected by ambient temperature change and stable oscillation can be achieved.
After optimum tuning is performed by the tuning mechanism using LED, the servo lock mechanism is operated to prevent the tuning deviation.

The tuning display at the time of FM reception shows the direction of frequency deviation (indicated by the red LED) and just tuning (indicated by the green LED) by three LEDs. By operating the servo lock mechanism at the time of just tuning, stable reception is always maintained.
The signal level of the antenna input is indicated by five LEDs for both FM and AM. The number of LEDs that turn on varies depending on the strength of the radio wave.

The AM section consists of an IF stage combined with a coil and two stages of a newly developed 3-terminal type high-selectivity ceramic filter and a double-series varicon. While eliminating 9 kHz beat interference, stable sound quality is obtained.
In addition, the antenna is a low-impedance loop type that is resistant to electric-field noise. This antenna is detachable from the back panel and can be installed in a suitable location depending on the receiving location.

Built-in oscillator for recording level check (440 Hz, output level : -6dB at 100% FM modulation)

Each function of FM/AM/Rec-Cal adopts electronic switching.

Power ON / OFF Built-in muting circuit to remove the following noise and inter-station noise.

Model Rating

Type	FM/AM Tuner
FM Tuner Section
Receiving frequency	76 MHz to 90 MHz
Antenna terminal	75 Ω, 300 Ω (Terminal Type)
Practical sensitivity	1.7 μ V, 9.8 dBf
S/N50dB sensitivity	Mono : 3.3 μ V/15.6 dBf Stereo : 30 μ V/34.7 dBf (μ V at 300 Ω, 0 dBf at 10-15W)
Image interference ratio	56dB
IF interference ratio	95dB(83MHz)
Spurious response	80dB(83MHz)
AM suppression ratio	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	mono:84dB stereo:80dB
Total harmonic distortion rate (1 kHz)	mono100% Modulation : 0.05% stereo90% modulation : 0.06%
Stereo separation	55dB(1kHz)
Muting action level	22dB
Output level	0.6 v (at 100% modulation)
Accessory function	Servo lock mechanism
<AM Tuner Section>
Receiving frequency	525 kHz to 1605 kHz
Antenna terminal	Terminal type with loop antenna
Practical Sensitivity (S/N20dB)	18 μ V
Selectivity	36 dB (± 9 kHz)
Image interference ratio	50dB
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 (equivalent to 50% modulation)
<Tuning instruction>
Tuning	Lighting display with 3 LEDs
Signal	Lighting indication with 5 LEDs
<General>
Power supply voltage	100 VAC, 50Hz/60Hz
Power consumption	7.5W
External Dimensions (Including Knob, Foot and Terminal)	Width 434x Height 93x Depth 300 mm
Weight	4.5kg