The term "RCA connector" is used to describe a two-conductor coaxial connector commonly used in consumer audio (HiFi) as well as professional audio. These connectors are also referred to as phono connectors or cinch connectors. The term “phono plug” refers to the cable connector that was commonly used to connect a phonograph to a preamplifier or receiver.
The name “RCA” is derived from the company that introduced this type of connector in the early 1940’s; the Radio Corporation of America. Originally designed for internal connections in RCA brand radio-phonograph equipment, the connector underwent further refinement and was adopted by other manufacturers as HiFi became more popular in the 1950’s. Today it is used for a variety of signals, including analog audio and video, as well as digital audio (S-PDIF).
The connector is a coaxial design, with a center signal conductor and an outer contact that can serve as both the signal return and shield connection for coaxial cable. The female connector is typically chassis-mounted and the male connector is typically cable mounted. The center pin extends past the outer contact of the male plug, and it acts as a guide to locate it properly in relation to the socket. Because the center pin is the signal conductor, this also has the unfortunate side-effect of making the signal connection before the ground, which can result in loud “hum” or noise during connection.
One of the most common forms of RCA cable is used for stereo analog audio. It consists of paired coaxial cables with the connectors on one cable marked with white housings for the left channel and red housings for the right channel on the other cable. The characteristic impedance of these cables is not specified.
A single cable with yellow housings is used for video and should be made with 75 Ohm cable best results. There is no guarantee that an inexpensive “video” RCA cable will be suitable for digital audio use.
There are also component video cables made of three coaxial cables with Red, Green, and Blue housings.
The original S-PDIF specification was superseded by the IEC 60958-3 standard, which includes an electrical and optical format. Electrical connections are typically made with 75 Ohm coaxial RCA cables, although BNC connectors with 75 Ohms cables can also be used. For best results, RCA cables specifically for “SPDIF” applications are recommended.