Why Does My Sound System Hum?

60Hz hum can occur in sound systems of all types.  Generally, this annoyance can be traced to your system's electrical connections.

For example, in a live sound reinforcement environment, you may have audio components setup on the stage, and other components setup at the house mixing position.  When using the facility's in-house power system, the power available on the stage may have a different ground potential than the power available at the mixing position.  This difference in ground potential can cause the 60Hz interference you hear as hum.

In this same example, powering the stage and mixing equipment from different legs of the facility's power system can cause the hum you hear as well.  When power enters a facility at 220 Volts AC, it is divided at the breaker panel into two legs of 110 Volts each.  The two sides of the panel are out of phase with each other.  If some of your interconnected equipment is powered from one leg, and other equipment is powered from the other leg, the resulting out-of-phase power connections can cause hum.

There are several remedies for this problem -- some better than others.  One remedy is to ensure that your entire sound system is powered from the same leg of the facilities main power system.  The best solution is to use your own power system which will tie directly to the facility's 220V power system, allowing you to break out your own sources of 110 Volts -- all in phase and with the same ground potential.

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