Balanced cables do reject common mode RFI hum etc, but that's only part of the story. The Krell has balanced circuits which means each channel has mirror image circuitry that drive the signal either positive or negative. Single ended components are cheaper because they contain only half the parts (nominally).
It would be a pitty to pay for a nice Krell and drive it with something single ended. However Pre amps like the CJ 17 and ART are only single ended and great preamps. So the balanced prejudice is like any other, only sometimes true.
It would be a pitty to pay for a nice Krell and drive it with something single ended. However Pre amps like the CJ 17 and ART are only single ended and great preamps. So the balanced prejudice is like any other, only sometimes true.