Hello diyaudio forum members - I am currently struggling to fix a ground loop/buzz in my DIY TPA3255 amplifier build. The amplifier board is drMordor's Akita "AllInOne."
It's an intermittent problem. I will do my best to succinctly describe the build and issues:
Amplifier and chassis details:
System details:
Problems experienced:
When I initially plugged everything up, the system worked perfectly with zero noise or hum.
To experiment with subwoofer placement, I unplugged the power to the sub and immediately got a very loud buzz in the main speakers.
I removed the subwoofer and any extraneous peripherals (TV, mini PC) from the power strip. Still got the buzz.
I plugged the amplifier into a grounded outlet via an extension cord - no luck.
Then I experimented with temporarily removing the safety ground from the chassis and separating the volume pot from the chassis to no avail.
I can get the system to work when the subwoofer is connected - as if the amplifier is "grounding" itself to the subwoofer - but then I discovered that I can make the system revert to the buzzing noise by flipping light switches elsewhere in the house (or the bathroom fan, for example).
I have done a fair amount of reading and have determined that I have a ground loop of some kind, but I'm unsure of how to proceed. Ideally, I believe the RCA ground would stay floated all the way until the amplifier, but it is being connected to the chassis at the volume potentiometer.
I would greatly appreciate any guidance or suggestions for next steps. Thank you!
It's an intermittent problem. I will do my best to succinctly describe the build and issues:
Amplifier and chassis details:
- RCA inputs are insulated from the metal chassis
- Alps potentiometer is grounded to the metal chassis
- RCA shield is tied to the ground pins on the potentiometer
- A safety ground is connected to the metal chassis near the IEC connector
- The PCB's ground plane does NOT connect with the mounting hole pads
System details:
- MiniDSP 2x4HD with 2x RCA going to amplifier and 2x RCA to active subwoofer
- Amplifier and MiniDSP are connected to a single power strip
- Outlet is NOT grounded - ground lift used
Problems experienced:
When I initially plugged everything up, the system worked perfectly with zero noise or hum.
To experiment with subwoofer placement, I unplugged the power to the sub and immediately got a very loud buzz in the main speakers.
I removed the subwoofer and any extraneous peripherals (TV, mini PC) from the power strip. Still got the buzz.
I plugged the amplifier into a grounded outlet via an extension cord - no luck.
Then I experimented with temporarily removing the safety ground from the chassis and separating the volume pot from the chassis to no avail.
I can get the system to work when the subwoofer is connected - as if the amplifier is "grounding" itself to the subwoofer - but then I discovered that I can make the system revert to the buzzing noise by flipping light switches elsewhere in the house (or the bathroom fan, for example).
I have done a fair amount of reading and have determined that I have a ground loop of some kind, but I'm unsure of how to proceed. Ideally, I believe the RCA ground would stay floated all the way until the amplifier, but it is being connected to the chassis at the volume potentiometer.
I would greatly appreciate any guidance or suggestions for next steps. Thank you!
Attachments
1 try running 1 rca cable to the subs. Bass is almost always mono.
2 when listening to FM radio from time to time I get a buzz. I have to squeeze the grounds on the outside of the rca cables and use a little bit of deoxit.
3 Ohm out the grounds on each rca cable.
4 Depending on which power amp I am using if I turn on the living room lamp (halogen) and use the dimmer I get a buzz. The lamp uses a simple diode as a dimmer. DC probably on the A.C. line.
2 when listening to FM radio from time to time I get a buzz. I have to squeeze the grounds on the outside of the rca cables and use a little bit of deoxit.
3 Ohm out the grounds on each rca cable.
4 Depending on which power amp I am using if I turn on the living room lamp (halogen) and use the dimmer I get a buzz. The lamp uses a simple diode as a dimmer. DC probably on the A.C. line.
It's working now with the potentiometer!
I wrongly assumed that the 2 ground pins on the volume pot were connected, but they are not. One pin was connected to the RCA input signal ground and the other to the amplifier, but there was not continuity through the potentiometer.
I simply soldered a wire connecting the two ground pins and it's working perfectly.
Thanks, all.
I wrongly assumed that the 2 ground pins on the volume pot were connected, but they are not. One pin was connected to the RCA input signal ground and the other to the amplifier, but there was not continuity through the potentiometer.
I simply soldered a wire connecting the two ground pins and it's working perfectly.
Thanks, all.
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