Basic Cable: Choosing the Right Cables for Your System Page 4
Audio Cable Types The standard analog-audio interconnects are coaxial cables terminated with RCA jacks. The advent of digital audio sources such as CDs and DVDs created a need for digital audio cables. There are two main types: coaxial and optical. Coaxial cable for digital audio is like any other but must maintain wide bandwidth and the standard 75-ohm impedance. Most sold specifically for digital audio also have gold-plated RCA connectors, but composite-video cables also work fine for this application. Some high-end components use the more secure bayonet-style BNC connectors for coaxial hook-ups. (BNC connectors also have the benefit of maintaining a true 75-ohm impedance, which RCA plugs and jacks, at closer to 40 ohms, can't.) Another alternative occasionally encountered is the professional AES/EBU interface, which requires balanced interconnects with three-prong XLR connectors.
Optical digital-audio interconnects, also called TOSlink cables (for Toshiba, which created the system), carry signals as pulses of light. Since they don't incorporate electrical conductors, they're immune to induced hum and electromagnetic and radio-frequency interference. Most use the small, squarish TOSlink connector, but there's also a smaller optical mini-connector that looks like a standard mini-plug.