Getting shocked by the pa

[bassmeknik]

Originally Posted by john m

The phases are marked so that all of the load is not put on the same phase--- load distribution.

Otherwise the stage would have been wired on one phase.

We primarily use the second leg (phase) for lights.

[robd]

another reason to go wireless

[tkonbass]

Originally Posted by robd

another reason to go wireless

Exactly.

I use a cord at rehearsal when I know the electrical system is OK. But at venues especially outdoor festival type shows it is wireless only. I haven't been mic shocked in twenty+ years and I attribute that to my wireless use.

This isn't to say that that it isn't a big deal or that electrical problems shouldn't be dealt with quickly and appropriately by qualified folks. There is still the potential issue of equipment damage or worse, real injury.

[Chipit]

Carry one of those cheap LED voltage indicators. Less than $20 and can save someones life, maybe even your own. Check between mic and instruments at every gig.

[amimbari]

Originally Posted by robd

another reason to go wireless

( this opinion is from a local amateur and not a fully staffed toruing band's contractual arrangements )

ok, so you get to the gig. You plug in. You look at your monitor-gizmo-wire-ground-fault-warning device.

Your RED-ALERT light is flashing....uh, ohh!!!

You are playing a 3000dollar gig at a party...uh,oh...!!!

you tell the owner that their wiring is faulty and you tell them you are cancelling the gig and losing the 3grand and to shove his gig up his ***...uh,oh...!

you use a wireless --the show goes on.

My point? years ago myself and the one guitarplayer were feeling the buzz at an outdoor gig. Tried every combo of plugs in the place...nope. TEMPorarily put a windscreen on the mics --the show went off without a hitch. FROM THAT DAY ON, I had a wireless. Outdoor/indoor/generatorpower -- no more shock.

I am not saying that is the ultimate solution, naturally proper wiring is the key, but ( as an amateur myself, so IMHO ) - who goes into the bar at the time of booking weeks/months in advance and puts a tester in every plug the band will be using and if there is a problem, they cancel the gig and lose the money??? And lastly and most important, if you do find wiring faults...do you report them to the city building inspector the next business day?

[john m]

Originally Posted by bassmeknik

We primarily use the second leg (phase) for lights.

If the one leg can take it.

[Chaddycakes]

So what do you do if there is a grounding problem at a venue? Try plugging the pa into a different circuit? The consensus is that windsock will help in a pinch, I guess.

[gareth dunster]

Can anyone explain how there is a potential difference between the grounds on different phases? I thought that the ground is common to all phases.

[john m]

Originally Posted by gareth dunster

Can anyone explain how there is a potential difference between the grounds on different phases? I thought that the ground is common to all phases.

In theory, ground to ground measurements should= 0 volts.

However, due to inductance and stray capacitance, potential differences (voltages) can be measured when the measurement is made at two different "ground points" of a system.

[two fingers]

Originally Posted by blaze17

You can test with a volt meter. With everything plugged in and turned on ready to go, touch one probe to the mic screen and the other to your bridge. Anything over 50 volts is considered hazardous voltage.

My singer/guitard got zapped pretty bad at an outdoor gig. Put my meter on it and had 70 volts. Bad extension cord was the culprit.

Depending on CURRENT levels, a lot less than 50 volts can knock your pecker in the dirt. AMPS (as in the measurement of current, not the big black boxes that make music) are much more of a problem than VOLTS.

Don't play another note in the place until you have the sound guy hold a guitar and explain to you THROUGH THE MIC why he won't fix it.

They are idiots and jerks for not caring enough to get it straight.

[john m]

Sure, low levels of current to the heart through a medical needle can kill you, but UL considers 50 volts the "lethal level."

My car battery can deliver 500+ amps if given a path of low resistance, but I can also lick my fingers and touch the two posts without worry--- only 12Volts potential difference.

Don't try that with the 100+ volts available in a light socket.

Originally Posted by two fingers

Depending on CURRENT levels, a lot less than 50 volts can knock your pecker in the dirt. AMPS (as in the measurement of current, not the big black boxes that make music) are much more of a problem than VOLTS.

Don't play another note in the place until you have the sound guy hold a guitar and explain to you THROUGH THE MIC why he won't fix it.

They are idiots and jerks for not caring enough to get it straight.

[bassmeknik]

Originally Posted by john m

In theory, ground to ground measurements should= 0 volts.

However, due to inductance and stray capacitance, potential differences (voltages) can be measured when the measurement is made at two different "ground points" of a system.

The other way a "ground" point may have unwanted voltage (referenced to another ground point) is from defective gear or from defective building wiring.


This was posted earlier in the thread but after reading the recent posts I thought I'd repost it. IMO it is required reading for any performing musician who must use a PA system in performance, And any guitarist/bassist who plays through an amplifier.

http://www.guitarnuts.com/technical/...fety/index.php