Balanced In audio, the opposite of Unbalanced. For us balanced refers to a type of AC electrical signal having two "legs" independent of ground. One is generally considered positive (+) and the other negative (-) in voltage and current flow with respect to ground. Unlike unbalanced audio lines there is no "signal" carried in the shield or ground connection unless there is a fault. The main benefit is that any noise that gets induced into the line will be common to both the positive and negative sides and thus canceled when it arrives at its destination, assuming the destination is balanced. This phenomenon is called "Common Mode Rejection" and basically just means that any signals common to both the positive and negative legs of balanced lines get canceled. This happens because when the receiving device looks at the signal the common noise actually shows up as out of phase with itself, and gets cancelled. Think of it as if the negative (-) signal gets inverted to positive (+) before use, which puts the desired audio signal in phase with the already positive other leg and at the same time causes the undesired common noise to become out of phase with itself. Clear as mud?
Balanced lines are generally much better for long cable runs due to their ability to reject induced noises. XLR and TRS type cables are designed to transmit balanced audio from one balanced device to another. A standard 1/4-inch guitar cable is an example of an unbalanced cable.
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TS (Tip Sleeve) and TRS (Tip Ring Sleeve)
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XLR
Trademarked name for circular 3-pin connectors developed by Cannon (now owned by ITT). "XLR" was originally nothing more than Cannon's part designation for the connector, which meant "X Series," "Latch," and "Rubber." In fact, you'll also sometimes see these connectors referred to as "Cannon" connectors. XLR has since evolved into a generic industry term, and many manufacturers now make this style connector. In audio work, XLR connectors are normally used for transmitting balanced mic and line level signals.
Pin 1 of an XLR connector is always ground/shield. The connectors are designed so that pin 1 makes its connection first when inserted in a jack; this ensures that the ground connection is made first, helping prevent pops and thumps in the audio chain.
Either pin 2 or pin 3 may be hot (determined by the gear the connector is plugged into), with the remaining pin being cold. To maintain correct polarity in a signal path, it is important to be aware of which pin is hot or cold on all connections, and wire your cables accordingly.
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A side note about XLR pin 2 and gear..
If you are running your gear on balanced XLR connectors, are they wired Pin 2 or Pin 3 hot? Although Pin 2 is more common in the United States, we do see a fair amount of equipment using Pin 3 for hot. If the hot connections are reversed by using incorrect cabling, problems will result!
Moral of the story: Know your gear!
Also for what it's worth. Know thyself