Hello, Gods' oracle. One question: I will be using the 567 filter IC to separate 12kHz signals from regular audio. The problem is that the 12kHz has a much lower amplitude. Should I amplify and then insert the full audio mixture to the 567, or will it be able to detect a much lower signal, at the right frequency ? Thanks in advance. Pedro. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.