Garfish's explaination is correct but not for digital connects only analog. The AES/EBU looks like a balanced interconnect but the AES/EBU receiver chips have not similarity to the balanced circuitry on the analoge side. AES/EBU shares the common mode rejection but that's about all with balanced. AES/EBU has a higher bandwidth then digital coax or optical and from an engineering perspective is superior. If a Coax cable sounds better its because the AES/EBU implementation is flawed on the particular pair of components. Also AES/EBU cables are more likely to sound similar (ie from cheap to expensive) because the engineering has more margin on bandwidth.
