Battery run bluetooth class d amp - help me fix the noise problem.
I am designing a small bluetooth battery powered portable speaker enclosure/boombox.
At the core of this design is a cctv li-ion battery that has 12v and 5v USB output ports. Its a great start to a boombox, or at least I thought it was.
From that battery, I am powering two things. A parts express Stereo Bluetooth Module, (running on the 5v USB) and a Lepai 2020 tripath amp, running on the 12v
Perfect you say. Thats what I said.
Plug it all together.... huge huge huge garbage noise, with digital clicks and beeps. All three components work fine on their own. The amp plays cleanly with bluetooth modules that have internal lithium batteries, the bluetooth module sends a clean signal to amps not sharing a power source.
I had a proficient audio repair man attempt to filter out the noise with resistors placed in numerous places, but it only slightly lessened the noise. Unfortunately I didn't document what he tried.
I have attached a photo of the setup (without the speaker attached)
I noted one thing... that if one was to connect the bluetooth using the rca input to the amp, if you only touched the internal rod to the inside of the female rca jack on the amp, keeping the outer shielding free from the amp, it would clearly make the noise, with no change in the noise when you pushed the plug all the way on, touching the outer shielding. That seems of interest. Yes?
Let me know if I can clarify any more of this. Any help would be most appreciated!