01-05-2012, 11:17 AM
I can imagine how you could make one easily from a pair of reaction condensers back to back on the same shaft.. or a little mental gymnastics reversing which parts you see as a pair and which parts move 
I have seen one only once.. in a VHF tv amplifier/booster thing where it was used as the output level control.
That is one strange circuit.. I can well understand why it doesn't work very well, in fact I'm surprised it works at all. What is more puzzling is why.. why design it that way when there are all the components for a straight forward volume control instead of making an uncontrollable oscillation machine as soon as it's not loud enough for the cup final.. It's hardly more than one step away from varying the filament temperature to control the output!!
I have seen one only once.. in a VHF tv amplifier/booster thing where it was used as the output level control.
That is one strange circuit.. I can well understand why it doesn't work very well, in fact I'm surprised it works at all. What is more puzzling is why.. why design it that way when there are all the components for a straight forward volume control instead of making an uncontrollable oscillation machine as soon as it's not loud enough for the cup final.. It's hardly more than one step away from varying the filament temperature to control the output!!
