Just for the sake of argument and continued edumucation, these are stolen from the Oade forum:
#71, "RE: DIY aes/ebu > spdif cable?"
In response to In response to 1
Hi!
It is more a matter of voltage levels than impedance. I would use a transformer, it is a good solution and allows your connection to meet spec, not a bad idea when daisy chains are involved. I have not tried it, but tapers tell me they use a standard XLR to RCA cable (wired for audio) without a transformer and it works.
peace...Doug
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#118, "RE: DIY aes/ebu > spdif cable?"
In response to In response to 7
Mike, another thing to think about is long term reliability of the chips. The S/PDIF voltage standard is 0.5 volts. Many use 1.0 volts, but the AES/EBU standard uses 9 volts. This might result in failure on some S/PDIF inputs as they only expect 0.5 to 1.0 volts. An output stage designed to drive a 110 ohm load will not be properly terminated into 75 ohms. The long term current sinking capacity of the output stage is another issue. I would not worry about it if I had to do it, but if I had a choice, I would use the transformer. Those pulse transformers are small and can be placed into an XLRM connector. I would use 75 ohm wire as that would allow me to add the transformer later. Probably worth the trouble...Doug