ACCESSORIES
RESOURCES
ELECTRICAL SAFETY FOR ENTERTAINERS:
Sound Equipment
Earth connections
Lack of good earth connections is the commonest electrical safety problem with sound equipment. Any item of equipment which is mains-powered should either be double-insulated (Figure 1) or correctly fitted with a protective (safety) earth.
If you are in any doubt about the connections of equipment, consult a competent electrician. Remember that an audio expert might not be expert in electrical safety.
Single items of equipment, if properly maintained, usually present few problems. However, if a number of items are connected together, it is possible that cable screens (the braided metal protective layer of the cable), together with
protective earths, form loops resulting in 'mains hum' on the system.
If this happens, do NOT remove protective earth connections. Removal of earths is one of the common causes of entertainers receiving electric shocks, some of which have been fatal.
Good quality sound equipment should not cause hum, although in some cases you may need to disconnect the screen at one end (only) of interconnecting audio cables. In other cases rearranging the equipment, so that the wires do not crisscross, can solve the problem. When obtaining new equipment, discuss your needs with the supplier. Some equipment has a facility for disconnecting the 'signal' earth from the safety earth without affecting safety.
Electricity supply
Sometimes it may be necessary to site a mixing desk at some distance from the power amplifiers, interlinked by multi-core signal cables. Microphones etc may have their own power supply (not phantom-powered from the mixing desk). It is preferable that all the different parts of the sound system are powered from the same phase of the electricity supply. If not, the risk of mains hum will be increased and people may be tempted to remove the earths from the equipment.
Connections
The terminals of amplifiers and the wiring and connections to loudspeakers may carry dangerous voltages (Figure 2). It is essential that wiring with adequate insulation is used, and that any connectors should be safe for use at the appropriate voltage and current.
