Hi. I have a problem with what I believe is a ground loop issue. The background is that I have a portable stereo which is dual battery-AC powered. A boom box, if you will.
This is a custom project of mine. I fitted a new amp module and the input signals was taken first from the volume control (via shielded cables) directly to the amp taking the original amp out of the circuit. But then I got this hum through the speakers. It is a steady and noticeable hum that can be drowned out if the volume is cranked up but when quiet, the hum is very noticeable. So I swapped the location where I took the signal directly from where the original amplifier chip was and there was no difference. As long as the signal wires are connected, there is the hum. If I disconnect all the signal wires, the hum from the speakers is gone.
The reason why I think it's a ground loop issue is because with the amp connected and powered by the boom box power supply -- if I feed an external signal to the amp from a portable CD player or ipod, basically anything not sharing the power source with the amp, then the audio is clear without the annoying hum.
Thinking it might be easier to avoid this problem by using the high-level (speaker level outputs) and converting to low level signal just before the new amp, that maybe I could correct this. But the issue persists.
Wondering if anyone has any thoughts or suggestions on this and what steps could be taken to correct this issue. It's driving me crazy!
This is a custom project of mine. I fitted a new amp module and the input signals was taken first from the volume control (via shielded cables) directly to the amp taking the original amp out of the circuit. But then I got this hum through the speakers. It is a steady and noticeable hum that can be drowned out if the volume is cranked up but when quiet, the hum is very noticeable. So I swapped the location where I took the signal directly from where the original amplifier chip was and there was no difference. As long as the signal wires are connected, there is the hum. If I disconnect all the signal wires, the hum from the speakers is gone.
The reason why I think it's a ground loop issue is because with the amp connected and powered by the boom box power supply -- if I feed an external signal to the amp from a portable CD player or ipod, basically anything not sharing the power source with the amp, then the audio is clear without the annoying hum.
Thinking it might be easier to avoid this problem by using the high-level (speaker level outputs) and converting to low level signal just before the new amp, that maybe I could correct this. But the issue persists.
Wondering if anyone has any thoughts or suggestions on this and what steps could be taken to correct this issue. It's driving me crazy!