Hum

A continuous low-pitched noise, usually at the mains frequency and its harmonics, picked up by the guitar's electronics rather than produced by the strings.

Hum has several distinct causes and each has its own cure. Single-coil pickups act as aerials for mains fields radiated by transformers, lights and screens, which is what humbuckers were invented to cancel. Poor shielding in the cavities, a broken ground on the bridge or strings, and a ground loop between pieces of equipment all produce variants that will not be cured by changing pickups. Diagnosing which one you have is most of the work.

Example: hum that vanishes the instant a hand touches the strings is the normal behaviour of an unshielded high-impedance circuit, not a fault.

Hum

See also