I'm designing a resonant filter based on a state variable filter topology with sweepable frequency and variable resonance. The filter is designed to sweep from roughly 20 Hz up to 20 kHz (50 kohm linear dual gang potentiometer with 50 ohm limiting resistors and 180 nF capacitors). The prototype works fine and sounds good however, both in the simulation and on the prototype, when turning the potentiometer to sweep the frequency band, 75% of the pot's turn works from 20 Hz to roughly 80 Hz or 100 Hz and the remaining 25% of the pot's turn sweeps up to 20 kHz. Is there a way to sweep the entire audible frequency band using one potentiometer while resolving the pot's sensitivity at high frequency? (cutoff frequency vs pot rotation).
Any help would be greatly appreciated!
Best Answer
Frequency is proportional to 1/(R*C), so it won't be linear with R.