For those of you keeping track..
the ‘metal can’ RCA -> XLR adapter combined with a ‘official’ SPDIF cable reduced drasticly, but did not eliminate, the noise. I take this as a encouraging sign that what I have is in fact a signal degradation issue rather than a protocol incompatibility.
One thing that I really don’t understand is why a 25-ohm impedence mismatch is giving me this much trouble? Of course, the other thing is I’m driving a unbalanced signal with a common-mode ground into a balanced input, which may not be the best thing for signal integrity ever.
My hopes are currently on the AES-i to AES adapter, it seems to be *exactly* what should be needed.
S.