Input ground loop hum only when p10 cables or XLR without phantom power are connected


I own a Scarlett 2i4 (USB interface) and all of a sudden a ground loop appeared that only makes noise when p10 cables or XLR cables without phantom power (when I turn it on, it disappears) are connected. I’ve changed the cables several times and nothing seems to work. Please help!
128x128pedropmk_
Hey pedro!

You may need to get the extra power supply for it if your laptop does not provide a high-current port. Just FYI.

Best,


Erik
erik_squires
A ground loop can't be fixed by noise filters or switching cables, or better shielding. You have to break the metallic contact in the loop
That's not exactly correct. What's needed is to get all of the grounds at the same potential. Breaking "metalic contact" is one solution.

erik_squires
Stereophile does all their USB DAC testing with a laptop running from battery power. I think it’s a boneheaded way to test DAC’s
Will you please explain why you think that’s "boneheaded?"
@cleeds I was being a little severe, but I still think it's wrong.

If you are testing a device which is often connected to a source of noise, such as a laptop with charger, you should test with that noise, not do everything you can to eliminate it in the test environment.

In effect you are denying those manufacturers who go out of their way to eliminate ground loops and digital noise the chance to shine, and putting them on a level playing field with DAC's that don't take the extra effort.