Audio and video cables and connectors

Audio and video equipment is joined by a variety of cables and connectors, each matched to the kind of signal it carries. On the audio side, line-level and loudspeaker connections use different cabling. Interconnects between devices commonly carry a low-level signal on coaxial cable with RCA phono or, in professional gear, balanced connectors, while loudspeaker cable carries higher currents between an amplifier and its speakers. A distinction is drawn between unbalanced connections, which use a signal conductor and a ground, and balanced connections, which use two signal conductors so that interference picked up equally on both cancels at the input, a method favoured for microphones and long runs.

Video signals come in several forms that need progressively more conductors. A composite signal combines brightness, colour and synchronisation into one connection, simple but limited in quality. S-video separates the brightness and colour information onto two channels for a sharper picture, and component or RGB connections split the signal further into separate colour components for higher quality still. Each format uses appropriate connectors, from the single RCA jack of composite video to multi-pin DIN-style plugs for S-video.

In much of Europe the SCART connector brought many of these signals together in one 21-pin plug. A single SCART cable could carry composite, S-video or RGB video together with stereo audio and switching signals, simplifying the connection between televisions and devices such as recorders and set-top boxes. Choosing the right cable and connector for each link, and using the highest-quality video format the equipment supports, gives the best result.

Frequently asked questions

What is the difference between balanced and unbalanced audio?

An unbalanced connection uses one signal conductor and a ground; a balanced one uses two signal conductors so interference picked up equally by both cancels, which helps over long runs.

Why is S-video better than composite video?

S-video carries brightness and colour on separate channels rather than combining them, reducing the artefacts that occur when they share one signal and giving a clearer picture.

What signals can a SCART cable carry?

A SCART connector can carry composite, S-video or RGB video along with stereo audio and control signals through a single 21-pin plug.