If coming thru your speakers its a ground.
There are many inexpensive devices to get rid of your ground loop if you cannot find the actual source of the problem.
Go to Amazon.com and search Ground Loop Isolator.

Hope this helps
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Outlaw 990/7700
Conrad Johnson Premier140 Tube Amplifier
Conrad Johnson 17LS MKll Pre Amp
B&W 803D2’s HTM3S DS7's
HSU Subwoofer
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Oppo BDP93
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Stack Variac
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