I agree with the suggestions of 75 ohm coaxial digital cable. I'll add that the length recommendation you may have seen in past threads here and elsewhere, indicating that a length of 1.5 meters (and not less) is optimal, seem to me to be technically well founded. See [url]http://www.positive-feedback.com/Issue14/spdif.htm[/url].
The degree to which that length is significant will vary, of course, with the jitter rejection capabilities of the particular dac, and with other system-related variables, but using that length can't hurt and may help.
Best regards,
-- Al