grab a ground loop isolator (tone sucking) or use better shielded balanced cables (even if its mono they will still loop back to your unit and cut the offending freq) or EQ out the offending frequency (tone sucking too)
removing the ground is a fucking retarded idea - YOU WILL DIE - the moment you take your rig into a area under heavy audio/visual load without a 3-Phase Power Setup by the Electrical Supply Board and theres a sudden spike your going to electrocute yourself (and die due to extremely high currents) and blow your device to a near impossible state of fixing it.
trust me i know, i studied it for 2 years with certs to prove it & i've dealt with it on numerous occasions not only in the land of audio/visuals
dont chance it