Ello peeps... I've also posted this in the design and acoustic s thread, wasn't sure where it belonged!

Can anyone tell me what sort of charge a control room output of a mixer could hold? I've been getting some nasty shocks from the patchbayand I'm pretty sure these are not static, as the charge sticks around for a while and lasts longer than your usual static shock. I was thinking that this could just be the normal charge that goes between mixer and amp stage. The patch leads I have have metal ends, could this be the problem?

I'm also worried this could be a sympton of a more serious problem. There is quite a hum coming through the speakers, which gets louder and quiter over time. Could it be an earth loop with equipment? Or could it be a problem with the mains supply?
The shocks come when I unpatch the control room out, which is connected to powered speakers. Earlier, when the patch cord came into contact with another piece of gear, which I presume earthed the charge, it tripped out the fuse box. This is all new gear and I have only just wired this lot together. I have checked that all the earth wires are connected in the IEC plugs.

I never had these sort of problems in the last studio I was in so I'm quite ignorant to the issues involved.

Any help or links would be greatly appriciated, cheers.