An unwanted electrical hum caused when two pieces of audio equipment have different ground potentials, creating low-frequency noise on the signal.
A ground loop occurs when two or more pieces of audio equipment are connected to the same circuit but have slightly different electrical ground potentials, causing current to flow between them. The result is an audible hum, typically at 50 or 60 Hz, that appears in the audio output.
Why it matters
A single unresolved ground loop can make a DJ rig sound unprofessional regardless of mix quality. Identifying it early, before a gig, prevents last-minute scrambling at the venue.
In practice
Isolate the offending piece of gear by disconnecting sources one at a time until the hum disappears. A DI box with a ground-lift switch inserted between the problem source and the mixer is the standard fix.
