eliminating ground loop

[ramki123]

Hi,

I have put together a portable bluetooth speaker. However there is a noise/hum as if my speaker is trying to contact its alien world. I thought its ground loop and try to eliminate it by breaking at the location 1,2 and 3 marked in the circuit. But no change. Sorry for a very rough diagram, but am not an electronic expert. So not sure which tool i should use to draw the diagram. Please can some one help on how to reduce this noise.

 

[FauxFrench]

With all three connections between the amplifier and the BTmodule cut, and the two inputs (L, R) of the amplifier connected to amplifier ground, do you still have the same noise?

 

[ramki123]

If i have understood it correctly do you want me to try merge L R signals to GND.

 

[FauxFrench]

Yes, connect R-input and L-input to input ground and disconnect all three wires to the BTmodule.

 

[turk 182]

is the blue tooth module in an case?


too many noise problems are called ground loops.... with rf devices the noise sources are harder to point and trace!!


are the supplies switchmode?

 

[scottjoplin]

It sounds like RF, doesn't sound like ground loop at all.

 

[sgrossklass]

In a setup with shared supplies as shown, I would be surprised if you did not get ground loop issues. The BT module and power amp share a ground connection, and there's an audio ground connection between the two. The moment the power amp PCB connects power ground and input ground, you're screwed.

If you can, get the BT module a battery of its own (should run a long time on 18650x2) and be done with it. A DPDT power switch is likely to be a good idea.

Other options would include a 5 V switch-mode converter than includes galvanic isolation, and hacking the power amp board to separate input ground from power ground, though it goes without saying that the latter requires that you sort of know what you're doing.

 

[scottjoplin]

Have you listened to the attached file?