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

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.

Some people call TRS connectors Tip Ring Sleeve. Those are not balanced. You need to make sure the 1/4 connector has 3 contact points, and that they are wired correctly.