I would like to add a A50k potentiometer to control the volume of an audio input for a small amplifier. Additionally, I used some easy passive filtering to remove the lowest frequencies and some highs from the signal.
This is the schematic:
simulate this circuit – Schematic created using CircuitLab
I understand that a potentiometer before the filter will alter the cutoff frequency of the lowpass filter. Adding the potentiometer behind the filter did not have any noticable effect.
Is it safe to assume that a potentiometer after the filter will not alter the frequency response significantly? The used Amplifier is a small PAM8403 board (see here). There is a 10k resistor at the input but I couldnt find any other information about the input impedance of the amplifier.
Best Answer
If you put the pot before the circuit and it is a high impedance pot then mid-band and mid-position, you will have a fairly high impedance pot loaded by R4 and R5. This can noticeably affect things so, in this position, the pot ought to be 10k i.e. much lower than R4 or R5.
If you put the pot on the output then it needs to be high impedance. This is because the series resistor R6 will not be unduly loaded by a high impedance pot such as 100 kohm.
Two scenarios but different pot values.
A 50k pot would best suit being connected at the output.