Wyred 4 Sound STmkII Series - Manual (Page 11)

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regarding a solution. NOTE: We only recommend using a ground isolator for trouble
shooting purposes, and it should be removed after the problem has been found and
resolved. Having the ground of any unit disconnected can potentially create a
dangerous situation.
An easy way to locate a noisy component is to replicate the problem and then
start disconnecting components one at a time, starting with the source end of your
system. Digital cable boxes and satellite receivers are notorious for making ground
loop hum. This is normally caused by the voltage potential on the input wire (shield
side) for either of the boxes when referenced to ground. If this is the case in your
system, the installation of an isolating transformer would be the easiest solution and
they are normally readily available at your local electronics parts store. A better
solution is a power strip with grounded and surge protected F-connectors that you
can pass your cable or satellite signal through.