Diagram Guide

Build a Variable Bandpass Audio Filter Circuit Diagram. This Variable Bandpass Audio Filter Circuit Diagram is a variable audio bandpass filter that has a low cutoff variable from about 25 Hz to 700 Hz and a high cutoff variable from 2.5 kHz to over 20 kHz. Roll off is 12 dB/octave on both high and low ends. R2-a-b and R6-a-b are ganged potentiometers for setting lower and upper cutoff frequencies, respectively.