These two schematics show the Volume Control and also a Low pass filter. The volume control is a very simple circuit you use a 100 k pot and a 15 k resistor so that the response is more linear. You could also use this volume control for other applications. I know that some cd players put out a siganl to high and you can hear it crackling in your speakers. This would work great to fix that problem. The low pass filter we made was to have it start dropping off around 200 hz. R1 and R2 are inccorect on the schematic. For R1 it should be 20 k and for R2 it should be 15k. This gives a cutoff of 195 hz. This filter produces a -40 dB drop.