Dedicated PSU for bluetooth to avoid noises.

[nicasiox2]

Hi, I once had an amplifier board (tpa3116) which was bluetooth built in. I remember the first times I tried it, it was clear sound, then I had to add some potentiometer extensions, around 5 inches of extension cable, and since there I had a noticeable buzz noise.

I have been reading some people having the same problem, they had the noise with no reason, and once saw a guy building a bluetooth speaker with two batteries section, he said that that was to avoid noises, which is common with dealing bluetooth amp boards, which made me think, so that problematic is adding a bluetooth board to our amplifiers?

How true is that? do all those bluetooth boards on ebay make noises?
Is it a must or mandatory to add a dedicated psu to the bluetooth module? or are there ways to use and share the same amplifier psu with bluetoothmodule and get everything ok?

 

[Rundmaus]

If the sound was OK without the extension cables for the potentiometers, the PSU will be unlikely as the source of the noise.

Noise is often created as interference coupling into high-impedance parts of the circuit. The parts around the input and volume pot will be high-impedance, so I would assume the added extension to be the reason for the noise.

How did you wire the extension? Is the signal cable twisted tightly with its ground return, or did you use a shielded coaxial? What about grounding, how did you route the signal ground?

A picture and a circuit diagram would help others to give useful advice.

Regards,
Rundmaus

 

[ICG]

I was thinking the same, interference most likely over HF signal/radio. Besides shielded coax cable, shielding cage (exclude the BT receiver though 😀) or filter network, there are often overlooked other solutions, like the mechanical extension of the potentiometer shaft or mounting a wheel and a belt or gears. Ok, the latter two are often overengeneered but the shaft extension is often a vaiable solution to shorten the signal path and reduce interference.