>> ----/\/\/\/\------|----- >> 3.3K | >> = .47uF >> | >> GND >> By the way you want the LPF's corner point at or below the lowest cord fundamental (~40Hz). Otherwise it will do nothing to remove that cord's second and third harmonics, which is what you're needing it for. Peter -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu