Audio cables in home theaters take the form of either analog or digital interconnects.

Typical analog cables consists of RCA or BNC coaxial stereo connectors and are characterized by a separate two-channel cable connection - one for the left and the other for the right signal; color coding is normally used to facility identification.

Digital audio interconnections may use either a single coaxial connection or a single optical connection - also known as TOSLINK. Optical connections use fiber-optic cables to transfer audio signals via pulses of light from a digital source.

Audio Interconnection Basics:

Good quality audio cables use an oxygen-free pure copper (OFC) conductor, designed to pass signals accurately with minimal loss.

Some may also feature the use of thick silver coating of the copper conductors to improve connectivity - in particular to help improve the connection between the conductor and the end connector.

Many audio cables also include two separate shields — a braided copper shield to guard against RFI, and one made of foil to guard against EMI.

In some cables, the shield is grounded only on the end that connects to the source, so that interference will drain away from the destination end of the cable.

These audio cables would incorporate directional arrows printed on their outer jackets, and should be hooked up with the arrow pointing away from the source (i.e. the arrow should be pointing in the same direction as the signal flow from source to load).

Connectors are extremely important to the overall cable quality. Good RCA or BNC coaxial connectors provide constant, high-pressure contact with the respective systems' connectors. The use of gold plated connectors in high quality audio cables is your guarantee for a corrosion free connection - thus ensuring  continued high quality signal transfer between system components that would not degrade over time.

End Connectors in Audio Applications

Note:

The above applies both to analog audio interconnects as well as digital audio coaxial cable interconnects.

"Coaxial" is a type of cable whereby the signal carrier (inner conductor) and its shield are aligned along the same axis (generally a signal wire runs down the middle of a cylindrical shield).

These same connectors are also used on video cables - this however does not imply that it's possible to interchange video with audio cables.

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Keep in mind that though digital and analog audio cables as well as video cables are very much similar in appearance, interconnects designed specifically  for digital or video applications will have to support a wider frequency response.

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Optical Digital Audio Interconnects

Optical audio cables are a special subset of audio interconnects that make use of  pulses of light to transmit signal information between system components.

(click image to enlarged) The Monster Cable LightSpeed 200 Tos-to-Tos Digital Fiber-Optic Cable For use with DVD, CD, Minidisc, DACs, S/PDIF, and Dolby Digital audio applications.

The most common type of optical connector found on home theater cables is the Toslink connector - shown on the right. 

Originally developed by Toshiba (hence Tos), this connector is usually plastic.

Some portable players make use of the mini-optical jack - an optical connector similar in appearance to the standard audio mini jack plug.

The main advantage of a digital interconnect is that these are practically  not susceptible to electromagnetic and radio frequency interference. 

Theoretically, these can come very cheap in comparison to regular metal interconnects, however, if you were to click on the image to the right for the Lightspeed 200, you will soon realize that when it comes to a quality interconnect, there is  a lot of high tech involved and obviously, a price to pay. 

This optical interconnect from Monster Cable feature graded index optical fiber to reduce jitter for enhanced definition, a spring loaded connector to keep fiber in correct optical alignment for maximum data transfer, and a metal-shell connector for long life durability. 

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