What are audio connectors?

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¼-inch (6.3mm) and ¼-inch TRS

Often used in pro-audio applications, this connector is also known as a phone connector. This is because it was used for years by telephone operators to patch telephone connections together. It has a tip/ring/sleeve design, like the 3.5mm connector, but it is larger in length and diameter. The 1/4-inch connectors may have only a tip and sleeve, or a tip, ring and sleeve (TRS). A TRS connection is used for balanced audio lines, or depending upon the equipment, for stereo sound. The 1/4-inch connectors are very common on musical instruments (especially guitars), and other staging devices such as effects pedals, mixing consoles, speakers, and amplifiers.

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3.5mm

The 3.5 mm connector is commonly called a 1/8-inch connector or a mini-plug. This connector is a small, thin metal plug that can be used to carry one, two, or even three signals. The tip of the plug is separated from the sleeve of the connector by a concentric band of insulating material. For stereo or audio/video versions of the plug, there may be one or two additional metal bands, called rings, placed between the tip and the sleeve. 3.5mm connectors are commonly used for computers and portable devices for mono or stereo audio. A computer's sound card uses these connectors for speakers, line-in/line-out connections, and also for microphones. Portable devices use the 3.5mm interface as a line-out connection for headphones or for connection to an auxiliary input on an amplifier. The "three-pole" version of the 3.5mm plug is often used on camcorders. This plug has a tip and two rings, which can carry video as well as right/left stereo audio.

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3.5mm Optical Mini Plug

Similar in size to the standard 3.5 mm connector, the 3.5 mm Optical Mini Plug is designed for digital audio application. This connector is commonly found on Apple® computers and some portable audio devices. This type of connector is often adapted to a standard TOSLINK® connector.

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Banana Plugs

Banana plugs are often used to make speaker wire connections on amplifiers, speakers, and audio wallplates. A banana plug has a metal pin that "bows" out in the middle, resembling the shape of a banana. Banana plugs are normally used in pairs and mate with binding posts, which are typically found on higher-end amps and speakers.

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RCA

The RCA connector is used in several audio applications. S/PDIF (Sony®/Philips Digital Interface) is the "red book" standard for digital audio signal transfer. A S/PDIF coaxial cable can carry linear PCM or multi-channel Dolby® AC-3/DTS® digital content. For dual channel stereo audio, two RCA connectors deliver the analog composite audio signal to the left and right channels of audio. In home theater, RCA is used as a powered subwoofer connection. In pro-audio applications, as part of an XLR to RCA cable, it can connect unbalanced sources to balanced XLR inputs for tape decks, CD/DVD players to mixing consoles and amplifiers, and can connect balanced line outputs from mixing consoles to unbalanced line inputs for recorders and amplifiers.

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TOSLINK®

TOSLINK is the name of an optical interface for digital audio signals. The interface was developed by Toshiba, and TOSLINK is their registered trademark. The TOSLINK (also known as EIAJ optical) connector is a small, round optical conductor housed in a squarish connector body. Originally intended for use solely with Toshiba CD players, it has been adopted by many other manufacturers and is standard equipment on many A/V sources, receivers and surround sound equipment. Even though TOSLINK uses fiber optic cable, it is limited to a maximum cable length of about 5 meters, due to the low power of the LEDs used in transceivers.

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XLR

The XLR connector is used for many professional audio applications. Originally designed by ITT Cannon, the most common configuration is a 3-pin connector for "balanced" audio signals. When male and female XLR connectors are mated, the design of the connector makes contact on pin 1 (ground) before any other pins. This prevents potential damage to the system. A balanced audio signal offers great protection against EMI noise, and can travel a long distance. For this reason, balanced lines using XLR connections are often used for microphones, mixers, amplifiers, and other pro audio devices.

Speaker Pins

Speaker pins are one way to terminate speaker wire connections. Instead of a wide body like a banana plug, a speaker pin has a straight, narrow shape. These pins are used to connect to push-on speaker connections found on many Consumer Electronics devices, and to 5-way binding posts.