DA-F680 : ¥ 42,000 (around 1978)
DA-F680S : ¥ 40,000 (around 1979)
FM/AM tuner with lock tuning circuit.
A lock tuning circuit is adopted to improve the detuning characteristics.
This circuit operates within ± 100 kHz from the tuning point, and the harmonic distortion and stereo separation do not deteriorate within this range.
The selectivity of the IF stage can be switched between WIDE and NARROW, and an independent two block configuration is adopted.
In WIDE mode, the newly developed 4-element ceramic filter and LC tuning circuit for phase compensation function as a high-S/N, low-distortion tuner. In NARROW mode, the four 2-element ceramic filters function as a high-selectivity tuner.
The harmonic distortion factor has been improved by adopting a discri transformer and a new PLL MPX IC.
It is equipped with a calibrator capable of oscillating a signal sound of 440 Hz at the same output as that of 50% FM modulation.
If this switch is turned ON before the FM air check and the input volume on the deck side is set to a range of 0 ± 2 dB, recording at the optimum level is possible.
The AM tuner section uses a discrete configuration using seven transistors and two diodes.
There were 2 types, the DA-F680 with the rack-mount carrying handle and the DA-F680S without the carrying handle.
|FM Tuner Section|
|Practical sensitivity||1.8 μ V (10.3 dBf)|
|Effective selectivity (± 400 kHz)||Wide:45dB
|S/N ratio (stereo)||Wide:77dB
|Image interference ratio||85dB|
|IF interference ratio||95dB|
|Spurious interference ratio||90dB|
|AM suppression ratio||Wide:60dB
|Total harmonic distortion factor (stereo, 1 kHz)||Wide:0.1%
|Stereo Separation (1 kHz)||Wide:50dB
|Frequency characteristic||30 Hz ~ 15 kHz + 0.5 -1.0 dB|
|Output Level / Impedance||0 V ~ 1.5V/5k Ω|
|<AM Tuner Section>|
|Practical sensitivity (S/N = 20 dB, bar antenna)||100 μ V/m|
|Selectivity (± 10 kHz)||35dB|
|Image interference ratio||50dB|
|IF interference ratio||40dB|
|Total harmonic distortion factor||0.8%|
|Output Level / Impedance||0 ~ 500mV/5k Ω|
|Pwer||100 VAC, 50Hz/60Hz|
|External dimensions||DA-F680 : 480 mm wide x 154 mm high x 400 mm deep
DA-F680S : Width 424x Height 154x Depth 389 mm