There are a variety of different audio connectors available. The most common types are 3-pin XLR, RCA, and 6.5mm TRS plugs (also known as ¼" jacks).
3-pin XLR connectors are mainly used for balanced audio signals. Using a balanced signal reduces the risk of inference.
Pin 1 is the earth (or shield)
Pin 2 is the +ve (or 'hot')
Pin 3 is the -ve (or 'cold).
There are a number of different XLR's: 3-pin, 4-pin, 5-pin, etc.
3-pin XLR Male
3-pin XLR Female
1/4" TRS Plug (6.5mm, AKA Phone Plug or Jack Plug)
There are two types of 6.5mm plugs: Mono and stereo. The mono plug has a tip and a sleeve, the stereo plug has ring, a tip and a sleeve.
On the mono plug the tip is the +ve, and the sleeve is the -ve or shield.
On a stereo plug being used for a balanced signal, the tip is the +ve, the ring is the -ve, and the sleeve is the shield.
On a stereo plug being used for a stereo signal (left and right), the tip is the left, the ring is the right, and the sleeve is the shield.
Jacks also come in various sizes - 6.5mm (¼"), 3.5mm, 2.5mm. The wiring for all of them is the same.
1/4" Mono Phone Plug (TS, Tip-Sleeve)
1/4" Stereo Phone Plug (TRS, Tip-Ring-Sleeve)
RCA (AKA Phono)
RCAs are used a lot for home stereos, videos, DVDs etc.
The RCA can carry either audio or video. It is wired the same way as a mono jack: The center pin is the +ve, and the outer ring is the -ve or shield.
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