I learned my "humming cable" lesson the hard way. Few years back my old cable gave up, so I bought a pair of "average" cables from a reputable major music vendor. When they arrived... I tried one. Humming. I spent hours, thinking grounding issues, mic connector, interface, faulty computer hardware, radio interference, aliens... Then I tried second "new" cable (from same mfg.) thinking maybe first was defective. Same deal. Thankfully I've decided not to purchase a new interface, instead bought a much fancier Canare Quad Cable L-4E6S with Neutrik Gold XLR. Humming was gone. 6+ years, still going strong.