I designed a special audio filter (unusual filter for unusual purpose. to make it short, I will not go into details, but I attached the schematic).
I would like to control one "parameter" (won't go into details) of the filter using a control voltage and I found, that using the Sallen-Key topology, exactly that parameters changes when I am changing the values the C1=C2 capacitors. **
So I wonder - would it be somehow possible to use varicaps (sometimes also called varactor diodes) in the place of C1 and C2 and control their value by adding DC bias voltage to the audio signal?
How would I do that?
Do I add the control voltage/bias to the audio signal? Or should I feed it into some node next to the vari-capacitors?
Also, I use bipolar supplies and so the audio is between -5v and +5v... and while the varicap is really a diode, that could also be a problem, as only half-waves would get through such vari-capacitor.
** or also when changing values of all the resistors, while sustaining the ratio between them. there are 5 resistors per stage and there will be at least 8 stages in the final circuits, so using VCA or a transconductance amplifier instead of each resistor would be quite insane.
I would like to control one "parameter" (won't go into details) of the filter using a control voltage and I found, that using the Sallen-Key topology, exactly that parameters changes when I am changing the values the C1=C2 capacitors. **
So I wonder - would it be somehow possible to use varicaps (sometimes also called varactor diodes) in the place of C1 and C2 and control their value by adding DC bias voltage to the audio signal?
How would I do that?
Do I add the control voltage/bias to the audio signal? Or should I feed it into some node next to the vari-capacitors?
Also, I use bipolar supplies and so the audio is between -5v and +5v... and while the varicap is really a diode, that could also be a problem, as only half-waves would get through such vari-capacitor.
** or also when changing values of all the resistors, while sustaining the ratio between them. there are 5 resistors per stage and there will be at least 8 stages in the final circuits, so using VCA or a transconductance amplifier instead of each resistor would be quite insane.
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