Late 2011 15" Macbook Pro I have an issue where my external monitors make noise when external monitor is connected at the same time. The second I unplug my secondary monitor from the Thunderbolt port then the sound dissapears. I am assuming its a grounding issue but I went out and bought a power conditioner to plug everything into hoping it would resolve my issue but no luck. Any ideas are always helpful, I will post if I make progress
Looks like I found the answer to my own problem. I tried to isolate the monitors power from the same power source of the speakers and had no luck. I then decided I had enough spare power cords for the monitor/speakers laying around that I would just break the third plug (ground) off the monitors power cord (the side that plugs into the wall. Well sure as sh#t this worked and the noise is gone. The additional ground was creating noise as expected.