Shock when going direct...grounding issue?

[Slevage]

A ground lift is a good option for an audio connection --- it is used to eliminate ground loops--- a common cause of hums. In industrial control circuits, the "noise" can result in problems with the digital control section.

The important part about "lifting a ground" is that the EQUIPMENT ground (sometimes called the frame ground, or safety ground) is NOT removed. The best solution is to have one common ground point. That is not always practical (backline equipment on stage, mixing board in the back of the venue). In these cased, the audio ground often has to be "lifted" to get rid of the 60 cycle hum, the third prong on the line cord still remains in tact. An outlet
tester or volt meter will verify that the building wiring is as it should be.

I have UL approved equipment with a ground lift switch on it. Speaking from experience---UL certification is not easy to get.

OK.... I think there is some bad info "floating" around here....

Facts as I understand them......

1) you got some form of shock from your amp. Almost certainly a "leakage" current shock.

2) This went away after you disconnected the wire going to the board.

Given that.... two things are apparently true.

1) For some reason your amp was NOT grounded. This could easily be due to the local wiring, and may not be an amp problem.

2) the board, or at the very least, the wire to it, was also not grounded. again, might easily be the farm wiring. (I know a thing or two about farm wiring, not much of it good)

If your amp was grounded, then any leakage from it, or from anything plugged into it, would have gone to ground, and you *could not* have gotten a shock.

If the board was grounded, or at least if the wire to it was grounded, then IT *could not* have caused any shock when plugged-into your amp. In fact if it WERE grounded, it might have grounded your amp and should have cured , rather than caused, your problem.

A ground lift is not a bad idea in general, but NOT a good solution to shocks, usually you want the opposite of a ground lift to cure shocks.... you want to ground the offending item.

If this is the only place you get this problem, I'd suspect the farm wiring.

That goes double when the board seems to have also been ungrounded.... the wire must have been grounded to the board, wires don't typically pick up that sort of charge from just laying around.

If you have access to any sort of ohm-meter, you can check by measuring resistance from the ground prong on the cord plug, to some bare metal on the chassis (with cord not plugged-in, of course). Should read basically zero ohms. If so, you are likely good. Shake the cord around as you measure, just to make sure it isn't in the one position that still works....

If you don't get a low resistance, nearly zero, double check by measuring between two spots on the chassis.... should read basically zero. If the cord is high resistance and two spots on chassis are low resistance, the cord is bad.... then you know what to do, right?