On Wed, May 14, 2025 at 08:28 PM, <Eli.rosenkim@...> wrote:
Good catch with the square wave, I noticed that right after posting. In any case the simulation results I was getting had to do more with horrible control leakage (louder than the input audio signal!) than with distortion. ...
I don't remember if I said this or if I edited it out of my reply.? I think the circuit may have been intended as a volume control, where the control voltage changes very slowly or not at all.? In that case, the RC filter they used was probably sufficient.? Because it has considerable feed-through from the control input to the output, it would not go well if the control voltage can change in less than a second, as you noticed.? I suspect it is fundamental to the circuit, not dependent on the transistor models.? It varies the supply voltage to the output transistors and I think it can't help but go straight into the output.
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Or, if this was for an electronic music synthesizer, the leakage might be treated as part of the overall sound effect, warts and all.
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I somewhat doubt there is a good way to actually reduce it, except with a balanced topology that provides cancellation, which is probably more than you can do with a CD4009.
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A very long time ago I lived within miles of Bernie Hutchins of Electronotes, but did not know it.? Maybe our paths crossed.
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Andy
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