KE7GKP:
If this is a fixed installation (a door-bell) then why are you running it from a battery?
Because right now I'm still testing various components, and it was easier to hook up a 9V battery to the breadboard. I'm testing things modularily - got the ISD1932 working on one breadboard, the xBee on another, now trying to get the amp to work on a third... This project is a long way from done.
Tried grounding the input to the LM386, no noticeable difference - the hum is still there, exactly the same.