PassiveFilter. - Here is Circuit Schematic Bandpass filter features adjustable Q and constant maximum gain as Passive Filter. Applications such as audio equalizers require bandpass filters with a constant maximum gain that's independent of the filter's quality factor, Q. However, all of the well-known filter architectures—Sallen-Key, multiple-feedback, state-variable, and Tow-Thomas—suffer from altered maximum gain when Q varies
The Original Article : "Bandpass filter features adjustable Q and constant maximum gain"