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VTTC - audio modulation
Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de>
I am running a VTTC, driven by a power tetrode. Plate voltage is
filtered DC. As I assume that I have maxed out the system, I am
aiming at audio modulation now.
I've tried some kinds of control grid modulation circuits already. The
result always was loud but rather distorted.
Therefore I would like to ask the more experienced coilers:
1. Does the tweeter become louder if the volume of the plasma ball
became larger? If yes, how should the toroid/corona shield look
like? Crown? Brush of copper wires?
2. Armstrong oscillators are self regulating and should resist any
type of modulation therefore. I have reduced the control grid current
already, but this helped a little only. Would it be better to operate
the tetrode in A-mode and to drive it from an external oscillator?
The control grid bias voltage could be provided by a fixed source
and would be superimposed by the audio signal for modulation.
Any advice would be appreciated very much.