I'm trying to seperate the frequency from the phase shift]/quote]
Impossible and for no reason.
How can i hook up a PWM circuit to a cap/resistor phase shift network ?
so i can vary the phase shift of the cap?
The PWM turns on and off a transmission gate. The gate is in series with the capacitor (or resistor) and applies it to the circuit for a selected duty-cycle.
The result is a small phase shift at lower frequencies and more phase shift at higher frequencies.
If the RC circuit is by itself then the result is a bass or treble tone contol.
If the RC circuit is in an opamp allpass filter then the result will sound like the original.
If the RC circuit is in an opamp allpass filter and is added or subtracted with the original signal then the result is a comb filter.