A local church had this problem for months .. replacing cables, rerouting them, etc.

One day they asked me to stop by and look at it. I pulled one of those old 3-hole to 2-hole outlet adapters out, put it on the end of the notebook power supply and instant quiet.

Simple poor mans ground lift.
Cost me 59 cents and 2 minutes; I keep a few in the adapter bag.


I do not work here, but the benefits are still awesome
Make your sound your own!