Balanced signals carry audio on two conductors with inverted polarity so interference cancels out at the destination; unbalanced signals use one conductor and are more prone to noise over long cable runs.
A balanced audio signal travels on three conductors: a hot (positive), a cold (negative, carrying an inverted copy of the signal), and a ground shield. At the receiving device, the cold is flipped back and summed with the hot, which cancels any interference picked up along the cable. An unbalanced signal uses only a hot conductor and a ground, so noise picked up on the cable reaches the output directly.
Why it matters
In a DJ context, the master output to a PA or booth monitor typically runs 10 to 30 meters of cable. Balanced connections (XLR or TRS) keep that run noise-free; unbalanced connections (RCA, TS) over the same distance can introduce hum or high-frequency noise audible over a loud system.
In practice
Use balanced XLR or TRS cables for any run longer than about 3 meters, particularly for the master output, booth output, and any send to a front-of-house rack. Reserve unbalanced RCA connections for short runs between gear at the same table, such as from a media player to a mixer.
