Bob Blick wrote: > If you read the original post. the solutions you are suggesting are > likely to do nothing, or worse, have side effects with other equipment. > Unless you can shut up the source of the interference(it's a neighbor, > so forget it) you need to deal with where it's getting in. I'm sorry if I confused you. I was suggesting diagnostic tools, not solutions. Until we know how the unwanted signal is getting into the system, it's premature to suggest solutions. Actually, from the OP's first post and immediate followups, it wasn't entirely clear what the invariants were with respect to the microphones and cables, or whether different microphone/cable positions had been tried. I was trying to suggest clarifying that issue in my first message. Also, it would be interesting to know what changed when the noise started to appear. Was that particular A/C newly installed, or did something change in the recording setup? -- Dave Tweed -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist