Sonsivri

I thought this might be an interesting little circuit that actually acts as a bandpass amplifier rather than a filter. I have seen many audio systems that have some sort of button or a variable resistor to increase/decrease Bass only, most of them use OPAMPs. This one was unique because it is so much simpler and yet effective. Originally adapted from the service manual of Sony XM-SD22X car amplifier. Might be digitally controlled if the POT is replaced by some sort of digitally controlled rheostat. Center frequency is 40Hz. It can be changed of course.