Hmnn, I've never had a "noise" or a humn from most of my system components over the years. Last year I upgraded to a matching Pass Labs amp/pre-amp and they come with shorting plugs on the balanced connectors. I don't hear any difference either with them in or out. that makes me wonder about Jeffcott's answer that XLR don't need them since they're balanced..., then why does Pass Labs, and probably other companies as well, bother putting them in their units? just curious.