Power Mains Isolation

ENS Audio said:

Easiest solution is to get an electrician to run a few dedicated 120v/20a circuits, done deal!  Chances are if the entire unit is wired for only 120v then the lighting circuit can be tied in with those outlets and being that it's a commercial unit more than likely you probably have those old fluorescent lighting fixtures which is what could more than likely be causing that hum and noise.  There is no telling what else could be wired on the branch circuit along with the outlet you're currently using.

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Pip said:

If it is a commercial space the fluorescent lighting is usually on dedicated power runs often at special voltages like  480/277 volt 3 phase 4 wire systems. So it is usually isolated. That being said all those ballasts are a problem and I would opt to change the lighting and use Variacs as dimmers when needed.

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