Turbowatch2:
It occurred to me when going home from work... to connect housings of pots with three wires directly to negative power supply.
I just came from upstairs to report the results and saw your advice. I was testing the amp and it's dead quiet as far as ground is concerned.
Now the amp only gives this hiss like ''ssssssss'' when I put ear closer to speakers but this is not related to ground.
You can't hear it from a meter or two or when music is playing so I guess it won't bother my father.
Thanks anyway for the advice.
'' The output filter problem could be minimized by running the output lead 2-3 turns through two ferrite rings, near the board. ''
Do you mean loudspeakers wires?
This would be the simplest solution.
Looks like the amp has some sort of filter (R-C filter ?) at the output but no chokes. I can see 4 resistors close to output but no caps. Could be the caps are under the heatsink.
It occurred to me when going home from work... to connect housings of pots with three wires directly to negative power supply.
I just came from upstairs to report the results and saw your advice. I was testing the amp and it's dead quiet as far as ground is concerned.
Now the amp only gives this hiss like ''ssssssss'' when I put ear closer to speakers but this is not related to ground.
You can't hear it from a meter or two or when music is playing so I guess it won't bother my father.
Thanks anyway for the advice.
'' The output filter problem could be minimized by running the output lead 2-3 turns through two ferrite rings, near the board. ''
Do you mean loudspeakers wires?
This would be the simplest solution.
Looks like the amp has some sort of filter (R-C filter ?) at the output but no chokes. I can see 4 resistors close to output but no caps. Could be the caps are under the heatsink.
Hi Igla,
I am also working on a tpa class d amp and faced these same issues, a lot of hum noise.
When I touch the Bluetooth board, its quiet and if I touch the pot knobs it gets more.
I am using an smps 24v 4a for the amplifier board and a 12v transformer dc for Bluetooth board, gain board and speaker protection board.
I know its a ground loop issue, But to where I should ground? To negative pins of power supply or to 3pin earth or to transformer center tap!!?
And also, is it required to ground the ground wire of audio signal?