Thanks Danny and Hobbs! I just want to make sure you meant .047uF, .033uF, and .022uF instead of .47uF, .33uF, and .22uF before I order some up. I do see some sonicaps for those values, but they seem to be much more rarely used than the .47, .33 and .22 uF caps. Also, for posterity as well as if I need to modify my filter for a different amp with a different input impedance - how did you calculate that?