Digital cable optimal length?

Nil -- If you are just using 44.1/16, based on my analysis above you should be equally good at 4m or 3m. It would probably be a good idea to try to cross-check that against actual user experiences, if you can find relevant information via search (here or via Google).

AES/EBU and SPDIF do not differ significantly in terms of protocol, bit rates, or clock rates, and therefore do not differ significantly in terms of the reflection effects we have been discussing. They do differ in terms of amplitude, use of balanced interfaces, etc., which would seem to favor AES/EBU (balanced connections, higher amplitude) for longer runs. Just as any longer run will benefit, in terms of noise immunity, etc., from being balanced and having higher amplitude (everything else being equal). But at only 4m, for a digital signal, I would suspect that the difference would not be particularly significant.

See the following, re the differences between AES/EBU and SPDIF:

http://en.wikipedia.org/wiki/Spdif

Regards,
-- Al

Al, do BNC or RCA type plugs exist that have a true 75 ohms impedance? And what kind of mechanical joint would you apply between the conductor and the plug (to minimize impedance mismatch): soldering or crimping?

Chris

Chris,

BNC's: Yes.

RCA's: Generally no; in a few cases maybe/approximately/sort of. :)

See the last few posts in this thread: http://forum.audiogon.com/cgi-bin/fr.pl?icomp&1233658634

As for crimping vs. soldering, I don't know; sorry.

Regards,
-- Al

YES- 75 ohm BNC and RCA connectors most certainly DO exist: Refer to the site URL that I posted previouly in this thread.

Rodman, I have to admit to a little skepticism about that Canare RCA connector. In the page you link to, a special joining method is cited as part of the 75-ohm connection. The RCA plug itself is not claimed to be a 75-ohm device.

Elsewhere I believe I have seen a Canare RCA plug which the company identified as "true 75-ohm", but this claim is in conflict with statements from other sources concerning the impedance inherent to the RCA design.

I certainly would like there to be a 75-ohm RCA plug and would be happy to be shown one whose impedance figure could be trusted beyond the shadow of a doubt.