Dumitru Stama wrote: > Now i have that mic-noise problem :) > I was thinking about a RC low-pass filter at the end of the third > stage to cut off everything above 3KHz. Condenser microphones are sensitive to sound pressure, not to sound pressure gradient. So, yes you need to sort of integrate the signal. MS -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist