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Electrical problems.

Ello peeps... I've also posted this in the design and accoustics 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 patch bay and 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.


Pro Audio Guest Sun, 01/23/2005 - 23:38
You need clean rectification of electricity from ac to dc. The problem is normally caused by transformer overload and wrong capacitor placements making the current to ripple hence cause the noise. DO NOT ATTEMPT TO REPAIR THIS YOURSELF. You need an electrical eng/technician to line up ypur equipment well and advice you on the correct transformers to use. The sittuation also shortens the life of equipment and can destroy your precious equipment at any time. so its a matter of urgency.