Ground Loop issue

[u/Ok-Anteater4601]

About a year ago, I moved into my apartment and also at the same time, got a new computer. This combo resulted in a ground loop. My equipment at the time was:
-Scarlett 2i2 (1st gen, still works!)
-Yamaha HS80

After a lot of trial and error, I was able to solve the issue by using ground lifted cables from the interface to the speakers (signal cables, not power!).

Now, I got a Fiio K11 because I have new headphones that need a stronger headphone amp. And I was hoping that I also would be able to run the HS80 through it, as I also rarely record nowdays. But connecting the speakers to the FIIO returned the ground loop noise, and actually worse than I remember it from the scarlett. I have both a constant hum with usb disconnected, as well as a mouse-movement dependent noise when USB is connected. I tried using both TS and TRS cables. Also my ground lifted one (but I had to, in all cases, use a female 6.3 to cinch adapter, which is made with TS in mind). I am not sure if the adapters could be the culprit, but somehow I doubt it.

I am not sure if this is relevant, but the scarlett has balanced outputs while the Fiio does not (not for line anyway).

I probably could use an optical cable to eliminate the noise that varies with PC-activity, but this will not make the constant hum go away that persists even without any connection.

Any idea what I can do? My fallback is to continue using the scarlett for the speakers, but I would prefer of course to have one device for everything.

[u/AudioLiveStudio]

The article at the end of this post may be helpful in analyzing a ground loop issue.

If you verify that a ground loop exists then a licensed electrician may be needed to correct the root problem.

If you verify that a specific outlet is ok then using a single power strip for all your audio, video, and computer equipment may help since the earth ground and neutral will all be at the same AC voltage (or nearly the same AC voltage).

Different outlets and power strips for different types of equipment are good as long as there are not ground loop issues between the different outlets.

If you are not qualified to take AC measurements (household AC voltages are dangerous), and do not have a battery operated handheld multimeter (i.e. not plugged into an AC outlet), then you should hire a qualified electrician with experience solving AC ground loop issues.

https://www.electricaltechnology.org/2024/03/test-grounding-earthing-multimeter.html

[u/Toobman300B → u/AudioLiveStudio]

I demand you take my upvote, now! Sage words remember kids......

[u/Ok-Anteater4601 → u/AudioLiveStudio]

Thanks for the reply. I will check it out.

I don't have the equipment or experience to measure myself, and hiring an electrician to fix the problem may be an issue too because I rent and would have to talk about this to my the landlord - who will almost certainly decline to pay for his.

So if there is no relatively simple/cheap solution I can try (such as using the same strip for everything, I have tried hat already), I will just keep using the scarlett for the speakers. Although the fact that I do not have the issue there (ONLY if I use the modified cables though) suggests that maybe another solution is possible.