Balanced connections use two out-of-phase signal conductors to reject common-mode noise

An unbalanced connection uses two conductors: a signal wire and a ground/shield return. Any noise induced on the shield conductor is added to the signal. A balanced connection uses three conductors: two signal conductors carrying the same signal with opposite polarity (hot and cold), plus a shield for electrostatic protection. At the receiving end a differential amplifier or transformer subtracts the cold from the hot; since induced noise appears identically (common-mode) on both conductors, it cancels. The signal (which is opposite-phase on hot and cold) doubles (+6 dB). Balanced connections are standard on professional equipment (XLR or TRS), essential for long cable runs, stage boxes, and multi-channel snakes where noise pickup is unavoidable.

Examples

A 200-foot stage snake carries 24 balanced mic signals from stage to FOH. Any RF, hum, or SCR dimmer noise induced equally on both conductors of each pair is cancelled by the console’s differential inputs.

Assessment

A DJ runs a 50-foot unbalanced cable from their mixer to the PA amplifier and hears hum. Propose two solutions. Which solution would be more permanent and why?