Possible ground loop causing interference noise

[Nayr]

I recently finished building the crack without speedball, and after some testing I think that there's a ground loop somewhere. When the amp is plugged into my onboard audio, there is noise that sounds a bit like electrical interference; the noise gets louder as the volume knob is turned up, and gains a high pitched body when I move my mouse. If necessary, I can try record how it sounds at high volumes. I also plugged it into the front of my O2/ODAC and had the same results.

I tested the amp with other sources (my laptop and phone) and the noise was not present. These devices were in the same area as my computer. I have tried unplugging a few things from both the mobo and the power strips that the crack is connected to. I've visually inspected all the joints but have not reflowed them.

Today I bought a ground loop isolator (onboard line out > isolator > 3.5 to RCAs > crack) and immediately the noise issues were gone entirely, even when at absurdly high volumes - there's only the expected faint hiss now. I've been listening to it for a few hours and it sounds great, no crackling or popping or anything. (... Although I did get worried because I heard popping at one point and didn't realise I was listening to a vinyl recording. Oops.)

• Do I have an actual solution? Or should I just reflow the joints even though they look okay? I haven't done this yet because I wanted to avoid inadvertently overheating things.
• How likely is it that it's not actually a ground loop with the computer and there's actually something wrong with the joints?
• Does anyone know if the average ground loop isolator can adversely affect sound quality? I bought one from Jaycar.

Thanks in advance. Sorry if there's any entirely useless info in here, I secretly have no idea what I'm doing yet and just getting started on DIY audio.

[Doc B.]

Yup, that is a good solution. Good work!

[Nayr]

Cool, that was easier than expected. I thought I was more bandaid fixing it.

Thank you Doc!

[Deluk]

I bought an isolator when trouble shooting ground loop noise in my HiFi system. Sort of worked but heavily rolled off the top and bottom ends to give a sound like very bad AM. I have only two wall sockets and kit was plugged into one and some the other. They really all need to be fed from the same socket. However, like many of us I think (hands up?) when you have 2 outlets and the need to feed 20 plugs or more, is an ongoing problem. There's always something new that wants mains power. I certainly have several adaptor strips but have had to lengthen some feeds to get them to the right wall outlet and so get rid of the dreaded ground loop. I'm glad it's only me who has to put up with the rat's nest of wires!

[Paul Birkeland]

A DAC fed by a toslink cable will also break these noise paths nicely.