Trying to figure this out. All I have in my rack is the ABM 500 EVO3, X2 wireless, and a korg rack tuner. At some clubs I will get a hum/buzz through the PA. So I'll change the outlet I'm plugged into and sometimes that eliminates the hum (speculating maybe on that occasion I was plugged in to the line the lights were on). Sometimes when I do this it doesn't get rid of the hum; however, changing my xlr cables fixes it. Alas, other times I can change outlets and xlr cables yet still am left with a hum buzz. I don't believe it's my amp, but maybe? I know the ground is supposed to be internal but I just don't know what can be done to where I don't have to worry about is my amp going to hum or not ya know? Any help.