I have the same issue with my EP500 my triggers cause my hum. Once I pull the trigger plug out hum is gone.
I removed the ground screws but it is still there any ideas??Hum is in all speakers/

RJ


M100 V4, VP180 V4,QS10s x4 V4 M2 V4 X2 EP500 V4 X 2,ADA 1500-3, ADA1250 - 7 N3