I'm not sure, either. From the posts I've seen here, it seems to only be particularly sensitive to ground loops when in unbalanced mode - the balanced mode (which makes full use of the differential design) is apparently the opposite extreme: not particularly sensitive to ground loops at all. I've suspected that the balanced mode is able to basically reject the ground loop hum (dealing with background noise and other electrical "harsh environmental" factors is what balanced cabling was designed for, after all). The unbalanced inputs would be their nature have to use only half of the signal path for at least the initial input section, and would then not benefit from that - making it more like a typical unbalanced design. As for why it appears more sensitive than other designs in that mode, you'd need to talk to somebody with a lot more expertise in electrical circuit design than me (my "circuit designs" are full of water or air - sometimes even hot air - not electrons).