Hi Edward: got a few questions for you: 1) Is the hum you describe actually a hum, such as a 60 cycle sound, or does it have a raspy, buzzy quality to it...some cheaper grades of electronic light dimmers inject this kind of noise into circuits that sound equipment will easily pick up (and may not necessarily be on the same circuit as the equipment, but on the same phase or hot leg in the breaker panel...they will also cause some lamp filaments to "sing")... 2) Is the equipment used by the client a piece of stand-alone gear, such as a guitar amplifier, or is its output connected to a P.A. system through a microphone input or a direct box (which could lead to the ground loop scenario mentioned), ... 3) if it is a stand-alone unit, does it hum when powered up with nothing else connected to it (possibly indicating bad filter capacitors in its power supply), and 4) Does the piece of equipment hum if it is connected to a different outlet, if one is available?
In many theaters, especially ones that attract road touring groups, a separate electrical service to the stage is provided for use with sound equipment, fed from a separate transformer from that which feed the stage lighting service. The transformer serves as a device to "decouple" or isolate the sound equipment from the stage lighting dimmers.
Just thinkin...
Mike (mamills)
[This message has been edited by mamills (edited 10-22-2003).]
[This message has been edited by mamills (edited 10-22-2003).]
