Hi Phil, The differences you're getting between the XLR and single ended cables are standard. I often do tests with the same cable, between the XLR and RCA versions. Mostly I get similar results to yours. The XLR has a deeper and louder bass, theres less extention at top end, with a slightly closed in sound compared to the SE, which in some cases, depending on the cables, it leads to muddiness in the mids which you might see as distortion. Sometimes the mids are just slightly sweeter with the XLR. But there definitely is a big difference between the sound of each output. rgds, david PS I am back to SE cables. Initially the XLR seems more impressive because of the extra bass ouput but with further A/B testing you'll see that the RCA is more musical and the XLR is more hifi and mechanical sounding.