"Serge Auckland" wrote in
message news
Short cable runs especially at line levels really don't
need balancing,

Really? You ought to try to measure the dynamic range of a CD player using
a completely unbalanced connection. Sometimes it works, but often the best
possible results are only obtained by using a balanced input cable on the
test equipment.

and it's something of a mystery to me why
some high-end consumer products like CD players are
offering balanced outputs

Its very often a cheap easy way to ensure the best possible dynamic range.

whilst phono inputs are almost invariably unbalanced,

The saving grace here is that the source(phono cartrdige) is usually
floating by virtue of being ungrounded, except at the input of the phono
preamp.