My question had to do with my DAC, but I came across this helpful info in an FAQ for the DEQ2496 at Behringer.com.
>>SPDIF (consumer format, unbalanced, normally characterised by the RCA co-axial connectors) is digitally simpler, whose basic information id unit utilises 4 bytes, (each byte being 8-bit).
AES/EBU (professional format, balanced, normally characterised by the XLR-type connectors) is digitally more complex, the basic information id unit being a differently structured 6 byte format (again each byte has 8 bit). The differences in impedance are not critical, but the fact the AES/EBU is both digitally more complicated and generally of a higher operating voltage means that AES/EBU signals will not be recognised by SPDIF (consumer) equipment.
It is however possible, although not guaranteed, that an SPDIF signal may be recognised by AES/EBU (professional) equipment. You can always test this on your own equipment by constructing an adapter cable (RCA - XLR). Because of the lower operating voltage of the SPDIF signal, this will not distort the signal or damage your equipment. (good reason for not trying it the other way around!) <<