I have been struggling with this for a while.
I am trying to create a simple stereo system with the PAM8403 amplifier, using a 3.7v lion battery and a 5v charger (both from a powerbank). This is the schematic I used for hooking it up:
This works pretty well, but when I plug in a micro usb charger there is a pretty loud hum noise and sometimes other strange noises. Seems like some ground problem or interference or something. I have tried adding capcitors and resistors to the power line but that didn't help. Can anyone explain to me whats happening and how to solve it?