Tuner analogico

Meant to be the center of the rig, the FM-only TU-500 has meters to validate the output level, a balance knob and even a NULL balance function.
Said meters can also be used as FM signal strength and output balance indicators... And, naturally, the TU-500 sports multipath and oscilloscope outputs.

The reason why everybody remembers the TU-500 is its scale display : a partly visible 12cm drum which not only allows to keep more front space for other controls but also to multiply the overall length of the scale - here at 28,3cm.

Inside is, 5-gang varicap front-end : the input first goes through a single tuning circuit (one gang) then to dual-gate Mos-Fet amplification, then to three gangs before local oscillator mixing and amplified via, again, dual gate Mos-Fets.

The modified Clapp oscillator circuit renders transistor functions insensitive to changes in the electrical supply voltage and temp changes ; the oscillator frequency is stabilized because the oscillator output is fed to the second gate of the dual gate FET.

http://www.thevintageknob.org/denon-TU-500.html

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