I don’t fully understand the science but seems to me like the whole setup was a floating ground input without the Bluetooth receiver being powered on which picked up interference from the power supply, and when the Bluetooth receiver was powered on, the existence of the source negated the hum.
@Jedi - looks to me like the potentiometer bodies on the amp boards were not grounded. I tried to ground them but was having difficulties.
I tried fixing the buzz by replacing the 2 prong AC adapter with a 3 prong AC adapter, but that didn’t help
For clarification, part of the original post was in error when I stated that all of my audio cables were shielded. The wires going into the amplifier channel and ground inputs were insulated 22 AWG wire, however, when I replaced them with shielded audio cable, the buzz didn’t go away. When I removed the input cables completely, the buzz persisted, albeit at a lower volume.
I solved the buzz problem with this setup, which doesn’t require the Bluetooth receiver to be powered on:
I split the main output of power negative with a conductor terminal block and wired up the ground prong of a 3 wire grounding plug with one end. With that plug in an outlet, neither speaker buzzes when powered on without the Bluetooth receiver being powered on.
I tend to come with unusual solutions to problems. Is my solution a known hack that’s been used to eliminate hum or buzz in audio circuits?
So, I solved the problem, and now if I ever decide to use the system without Bluetooth, the speakers will not buzz, but I still don’t understand why the powered Bluetooth receiver eliminated the buzz.
@Job_Jalink - knowing the fix to my buzz problem which doesn’t require powering on the Bluetooth receiver, as well as the additional information I provided, are you able to explain what the powered Bluetooth receiver did to eliminate the hum.
Also, I’m thrilled that I solved the root problem, but can you please explain exactly why this works, as well as why switching to the 3 prong adapter did nothing to eliminate or reduce the buzz?