If this is a fixed installation (a door-bell) then why are you running it from a battery?
Quote from: KE7GKP on Jul 24, 2011, 02:16 amIf 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.
Then you have an unstable LM386 circuit. 1) Test with the inputs shorted to ground. i.e. pins 2 and 3 connected to pin 4. Does it still oscillate?
2) Did you use a filter/bypass capacitor across the power (pin 6 to pin 4)?
3) Did you use the recommended snubber circuit, 0.05uF and 10 ohms from output/pin5 to ground?
4) Are you using the recommended output capacitor, 250uF?
5) Are you using a capacitor across the gain-setting pins (pin 1 and pin ?