I'm using a Bluetooth Module and Amplifier module to play sound through my phone.
Bluetooth Module : Bluetooth Bee USB to Serial port Adapter FT232RL - Blue - Free shipping - DealExtreme
Amplifier Board : http://www.dx.com/p/2-channel-3w-pam8403-audio-amplifier-board-red-146300#.VY7ntPlVikq
I've got the audio output of the Bluetooth module connected to the audio in of the amplifier board where speakers are attached. When these boards both have there interdependent power supply's the audio is very clear without noise.
When I power these modules both from the same power supply I get a humming and a lot of noise on the speakers.
I've looked into the concept of ground loops but struggle to apply it here. Can I power these boards from the same power supply? could someone explain why a group loop could be causing this problem?