KE7GKP:
Then you have an unstable LM386 circuit.
- Test with the inputs shorted to ground. i.e. pins 2 and 3 connected to pin 4. Does it still oscillate?
Will check tonight for the oscillation. Earlier, when I was just dealing with the noise/hum, I tried grounding pin 3, with no appreciable results. Haven't tried that since adding the bypass cap and getting oscillation. Pin 2 has been grounded all along.
- Did you use a filter/bypass capacitor across the power (pin 6 to pin 4)?
No. Since I'm using a battery power supply, would a filter on the power leads accomplish anything? I will try that tonight in any event.
- Did you use the recommended snubber circuit, 0.05uF and 10 ohms from output/pin5 to ground?
Yes.
- Are you using the recommended output capacitor, 250uF?
Yes.
- Are you using a capacitor across the gain-setting pins (pin 1 and pin 8)?
Yes, 10uF.
As I said above, I'm using exactly the circuit from LM386 Schematic diagrams (which is from the datasheet IIRC). The second one (200 gain).
Thanks for the help, I'll continue poking at it.