PC digital audio connectors

These come with identical data but different electrical properties;

TTL 5 Vpp 2 to 4 pin connector
SPDIF 0.5 to 0.6 Vpp in 75 Ω RCA
TOSLINK Optical JIS F05

With a good quality cable such as RG59 long SPDIF cables can be used. I recommend the use of BNC connectors in combination with BNC to RCA adaptors.

Links