Ground

The common reference point in a circuit that all voltages are measured against, and the route by which unwanted noise is sent away.

In a guitar the strings are normally connected to ground, so that touching them discharges the small amount of noise the player's body carries as an antenna, which is why a guitar hums more when the strings are not touched. Shielded cavities, grounded bridge plates and a properly earthed output jack all serve the same purpose. A poor ground shows up as hum, crackle when a control is touched, or a signal that disappears when the jack is wiggled.

Example: a guitar that hums loudly until the strings are touched and goes quiet with contact is working as designed, not faulty.

Ground

See also