• The filter passes only a narrow band of frequencies
• The center frequency is fixed by the 22 nF capacitors and resistor values
• The Q control adjusts how sharply that frequency is emphasized (Upper potentiometer)
• Two op-amps are used to:
• generate the band-pass response
• control resonant feedback cleanly and stably
• Use the lower potentiometer to adjust the central frequency
This is exactly the architecture used in parametric equalizers, where frequency, gain, and Q must be adjustable independently.
