Eldartford: My own experience with balanced connection in general is much like that of Jfrech and Sayas. I'm speaking specifically here of running a balanced source (in my case, a DAC) into a balanced preamplifier and doing instantaneous, level-matched A-B comparisions between balanced and single-ended connection. My assumption is that if there can be a worthwhile improvement with such a robust source (in the sense of output level and resultant S/N ratio) and short, well-shielded interconnnects, it stands to reason that a potential improvement at least as great, if not greater, could be had for a phono connection. And with the preamplification of the phono signal, again, the high gain factor required would lead me to believe that if balanced amplification is beneficial anywhere for its noise- and distortion-cancelling properties, it could be even more so here.
When it comes to sources other than phono, much gear does not offer a true balanced output, and to do so would necessarily be more costly, all other things remaining equal. So my holding the impression, reinforced by some audio writers, that all phono cart's, as a catagory of source, were naturally balanced devices as-is, to me obviously begged the question. To say there's not a 'problem' with single-ended connection and therefore we needn't worry is to miss my point - improvement is improvement, especially when it's conceivably available without having to start over with a new source (cart) purchase. Phono is noisy. I'm just trying to see if this is a way of making it less so.
