Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: yorgle on December 06, 2019, 10:26:31 am
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I'm currently using this circuit in two of my SE amps. In each amp, the tremolo "signal" wire is connected directly to the grid of a preamp tube. Should there be a coupling capacitor on this wire? I assume the answer is "no" because both amps work without caps, but looking at schematics of other tremolo circuits, eg Gibson GR-1rt, there is always a cap when the signal is inserted into tube grids. As an experiment, I stuck a .01uf disc on one of the amps and it killed the tremolo, so again, I assume the answer is "no" but I'm confused as to why a coupling cap isn't used here. :dontknow:
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In the GA-1RT the tremolo signal is taken from the plate of the oscillator tube so the trem signal is riding on a big DC voltage. The cap is necessary to block that dc voltage from appearing on the grid of that 6V6.
The Trem-O-Nator output has no DC voltage nor even an AC signal voltage. The output is just a varying resistance that shunts the guitar signal to ground. The VTL-5C1 optocoupler isolates any voltage that appears on the LED side from appearing on the LDR side. So, no coupling cap needed.
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Thanks for clearing some fog from my head. Seems perfectly clear to me now.