+1
And on top of that, most off-the-shelf "balanced receivers", iow diffamps for pro-audio boxes, are inherently imbalanced by the nature of their design (impedance/curent mode imbalance by 200%)
I'd write about it myself, but here's a blogpost explaining the situation:
http://www.edn.com/electronics-blogs/analog-ic-startup/4403059/Balanced---audio-line-receivers-and-the-physics-of-fields
My 2c: if you roll your own, you can compensate for said inherent defficiencies, with clever choice of resistors or using some other totp, the most "fool-bulletproof" design being a dual-inverter topology, but not necessarily best from audio POV. Superbal is good but itchy with fast opamps..
Some types of connections while claiming "impendance balance" are in fact, if you look at it this way actually a "remote-sensing" receivers, compensating for dirty connections (gnd currents etc.)
"Balanced receivers" actually don't "sum", but they substract signals, a - -b (twice neg. becomes 2x the value)