Hum and 2 vs 3 prong power cords

I have a hum issue with my HT. i don't want to bore people with the complex details so I'll get to the point.


I have 5 separate circuits in a sub panel. This sub panel is not totally separate from the main panel.

I have 3 power amps: Anthem MCA 3 (RCA/XLR), Aragon 2005 (RCA only), Classe CA-150 (RCA/XLR). The least offensive is the Anthem. The Aragon and the Classe both hum to varying degrees and uses a three prong power cord. The Anthem uses a 2 prong power cord and doesn't hum at all.


The interesting test is when I plug the Aragon or the Classe into a cheap 3 prong automotive/outdoor extension cord. The cord is somewhat defective because when I rock the plug/extension cord connection, the hum goes on and off. When I plug either amp straight into the wall, it hums.


My question is this? Is it dangerous to me or to the 3 prong amps, if I remove the ground pin on the 3 prong plug? Will static build up or will I get shocked? The Anthem has 2 prongs and it never hums. And I'm guessing the ground connection in the automotive extension cord is wonky that's why I can make/break the ground connection.