A “ground” is a return path that channels stray electricity to the earth after a power surge strikes. Lengthy runs of unshielded and untwisted wiring — or improperly arranged electrical and grounding systems — may develop antenna-like qualities and act as conductors in your AV setup. This can disrupt your display or sound when crosstalk, EMI (Electromagnetic Interference), RFI (Radio Frequency Interference) and other types of external disturbances are generated.
A full system approach is recommended to best address these power quality issues. Surge protectors are designed to defend a building’s interior and exterior electrical systems. Isolated ground guards AV equipment. Receptacle Testers are handy tools that address incorrect outlet wiring. Signal transformers lower “noise,” the haphazard electricity within a circuit that produce “hum” or “buzz” within audio transmissions. This also makes “hum bars” develop on video displays. Unbalanced interfaces can cause excess noise if a ground wire does not transmit its full signal, with the RCA Connector used in audio and video sometimes susceptible to this issue.
The National Electric Code (NEC) —updated every three years — should be followed in its entirety as a resource for safe grounding guidelines to properly maintain audio, video and other electrical systems. A ground should also never be bypassed for safety reasons; and ground rods should at no time be placed next to rack equipment, which can become a conductor itself.
It is helpful to be armed with knowledge about common and differential noise types. Common mode noise travels along a conductor pair’s same path, while differential mode noise journeys in opposite directions on each conductor pair. Improper signal wiring and equipment with low common mode rejection rate (CMRR) can cause ground loop problems when noise and ground electricity travel on the same path.
It is also critical to know the differences between electrical service phases, with three-phase systems within large commercial buildings; and single-phase 120/240V and 120/120V services in smaller commercial structures and residences. Single-phase 120/120V is best for AV systems.
Download the Middle Atlantic Products, Inc. PDF guide here for complete information on grounding systems.