How much/what electrical danger performing on a covered stage during rain?

Phil Allison wrote:


There's no danger to the user of doubly insulated devices. They are safer than grounded appliances.
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"Fred Bloggs"

** That is CRIMINALLY INSANE BOLLOCKS !!!!!!!!!!
It is COLOSSALLY DANGEROUS to use a class 2 item after it has become WET !!!
The Bloggs goon is a TOTAL MORON !!
....... Phil
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Hello Phil,
Phil Allison wrote:

Would you care to tell us why instead of insulting the original poster (which, in my opinion, is very unprofessional, as is "SHOUTING" in a news posting)?
Maybe if you'd explain the danger of using a class 2 item, someone would listen to you?
bye Christian
PS: Sorry for X-posting, but I think that it is of no use to set a "followup-to" after so much X-posting harm is done.
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"Christian Marg"

** You have not read what I wrote & you do not know what an utter PITA Bloggs is.
Try reading the user instructions and warnings for a class 2 audio appliance.
Try explaining how a WET class 2 item of sound gear is still safe to se - go on.
...... Phil
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Christian Marg wrote:

Ignore Phil. He hasn't had his morning bowl of medication for his mental problems.
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If the local organisers supply your power in IMO it's essential to check it out yourself first, carry your own earth leakage trip but preferably run on your own mains cable. I now carry a small plug in tester that checks correct connection & measures earth loop impedance. Several years ago at a ten piece gig in Tain Scotland on a truck bed with canvas shelter, the mains supply provided had the live and ground transposed! I traced the cable back originated from a three phase board in an open tent with the cabinet doors fully open, that tent was open to the public children could have wandered in ! After ranting to the organiser and sorting it all out we found out half way through the gig that the canvas cover leaked like a sieve.. There was a good sized audience mostly with umbrellas, so we kept the show going after covering up the gear. Now I always run my own cable out and use own earth leakage trip and run the tester first. We have had requests to return for repeat gigs at that location - we've refused, never again.
Mike
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The reason that this kind of thing happens is either because the ground on the electrical power service is bad, and nobody has checked it, or because somebody has specifically defeated the safety ground on some piece of equipment.
A special case of the safety ground problem is the old guitar amp that never was built with a safety ground, just a 2-pin plug. Some of those are even hot chassis. You plug it in, and the chassis may be floating way above ground, and when you pick up the guitar you are too. Touch the grounded mike and you get a shock. These amps need to be fixed and modern grounded cords installed on them.

Hire competent sound crew. If you ever, ever see a 3-to-2 prong "cheater" or an cord with the ground lug lopped off, you are not dealing with a competent crew and it is time to leave before someone gets hurt. Look at the backline amps too.
If this is an outdoor festival, there is probably a seperate group of people in charge of power distribution and management. Talk to them.

You mean like stage risers that collapse and injure people? --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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best bet is a wireless mic.....if there are no wires attached to it, you are basically totally safe.
next best bet, if you have to hold a wired mic, do not touch anything else metal and do not have your feet wet.
if the mic should be live, you won't be shocked unless you touch another metal object or you are grounded through wet feet...
if there is lightning around I would use ONLY a wireless mic. touch nothing that is wired or connected to anything.
Mark
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I all honesty I have not in 20 years of live sound seen a single"live mic" I have experiacedproperly grounded mic when a "live" guitar player touches the properly grounded mic he get a shock but its NOT THE MIC that has the juice its the player who is"live' AND THE CURRENT FLOWS TO GROUND THROUGH THE MIC BUT THE mic does not SEND THE SHOCK TO THE PLAYER gEOGRE
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Assuming that the sound system is properly grounded this is true. The exception is the sound guy that had a ground loop that was causing the system to hum no matter what he tries tio do, so he removes the grounding on some items in the system to fix it. A long as all of the equipment gets tied together by the shields, and they find ground somewhere in the system, you should be OK. But it is considered to be a very bad practise these days.
There was a time when nothing had a ground on it, and the AC connectors weren't even polarized. Engineers doing any decent sized instalation (radio stations for instance) would actually design their grounding system and connect a wire to the chasis of each piece of equipment and run that back to a common ground that ultimately found it's way to an "earth ground" as in a long copper clad stake driven into the directly into the dirt. Everything had ballanced ins and outs and most of the cabling inside the racks only had grounds connected at the input end to allow the earth ground from having multiple paths.
When they started putting grounds on power plugs, the engineers hated it because the additional ground connections screws up their carefully designed grounding schemes. The first thing they did when a new piece of equipment came in was gut the ground pin off of it.
I think it may even be illegal to remove the ground pins now.
David
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Dasvid McCall wrote:

The next thing we did, particularly on a remote, was to "reverse the plug" to get rid of ground loop hum. Very few of the old units had "polarized" two blade plugs, and the "adapters" had an unpolarized two blade plug.
Probably the only reason we didn't kill somebody was that there were few "musicians" plugged into high power amps!
--
Virg Wall, P.E. (One-time broadcast "engineer".)

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Your engineers cut the grounds off the plugs ????? Glad i don't work with those engineers!!
A proper design will factor in the use of current as well as older style equiptment (which would include the recomended plug style)
Current equiptment requires the upgrade of all lines & such and therefore - in this world of 3-prong plugs - design has changed.
I can only hope that your engineers have stopped cutting the saftey factor from your equiptment.

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We're talking early 60s and these guys were a lot older than I was, so I'll bet they stopped by now (probably stopped for good by now).
Everything was grounded separately in a carefully designed scheme to eliminate ground loops, just not with the power cord.
David
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Some guitar amps had a switch that allowed you to switch which side of the line would be referenced to the chasis and shielding. It wasn't a direct connection though, it went through a capacitor so the current was limited to a trickle. After you connected everything up, you would try the switch in both positions to see which side gave you the least hum.
David
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We call these people "idiots" and "unsafe" and I have seen more than one guy fired on the spot for doing precisely that. This is not an acceptable behaviour.
We have plenty of iso boxes with 1:1 transformers that allow anyone to break signal grounds at any point. Anyone that does an outdoor festival without such things is not competent.

It has ALWAYS been considered to be very bad practice and you can NEVER count on signal grounds providing a reliable safety earth. This is in part because signal lines are always being moved around and someone may briefly disconnect and repatch one. When you see a spark when you repatch a cable, something very bad is happening and equipment is bound to get damaged.

And this can be a very reasonable configuration for a permanent installation as long as EVERYONE recognizes the grounding scheme and follows it (and that may require an orientation for new hires). It is not reasonable or reliable in field operation, nor has it ever been acceptable in the field.

It has been against the NEC here in the US, at least since the early seventies. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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wrote:

I'd agree with that.

Back when I was doing concert sound in the late 60s these things were available, but not at all common.

I agree with that as well. Sparks and smoke are 2 things we are all better off without. Unless you live in GB where you depend on sparks to deal with your lights :-)

Yes, field equipment gets swapped around too much to use this approach, but as you say, it is against regulations to remove grounds, which makes grounding schemes in permanent racks more complicated than it was.

That sounds about right. I don't remember grounded outlets being very common in the early 60s and don't remember any in the 50s. I still run into quite a few outlets with no ground even today. If you are lucky, the box will be grounded and you can just use an adapter. If the box isn't grounded, then I guess you should start looking for a water pipe.
David

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Part of that is because in the late 60s, everything was transformer-isolated and there was already a transformer in the input and the output of the console and on the input of the amp. So telescoping a ground was all you needed to do to get transformer isolation.
These days transformers are too expensive and folks often consider them too much of a source of possible audio degradation for everything to come with transformer-isolation. So instead we have more iso boxes on the truck.
In the sixties, here in the US, if you knew someone that worked at the phone company you could get them to bring you "repeat coils" which were used for long distance circuit isolation and loading, and which were some of the best audio transformers available at the time.

In the US, you see a lot of those in homes, but not many left in commercial locations. They turn up in old churches, though, as do things like DC outlets... --scott
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what i find more than I care ton is some yahoo removes the 2 slot edisons and replaces them with the grouded version , only there is no ground connected on the back
every outlet get tested before it gets used George
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snipped-for-privacy@panix.com (Scott Dorsey) writes:

Does anyone use 1:1 120v isolation transformers?
Doesn't folks plug EVERYTHING into a GFI? If the GFI is tripping, You Have a Problem -- fix it.
Clearly what's needed is fiber-connected mikes, both vocal and instrument...
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Sometimes, but the NEC in the US limits what you can do as far as breaking safety grounds, when isolation transformers are in use. Normally folks use isolation transformers only as low-pass filters, really.

NEC says you have to use GFIs on most circuits outside, but not everyone does. Personally, although GFIs are prone to falsing in high RFI environments, I think they have saved more lives than they are given credit for.

Yes, but now you need to get power to the mike, as well, since the fibre can't carry it. There are plenty of systems with fibre links between the stage box and the console; you can see one at the National Gallery of Art in their sculpture garden system. Plenty of isolation, and you can run the skinny little fibre into an existing power conduit rather than having to pull a big snake. Of course you now have to set the console trims on the stage box which can be a pain without a big stage crew. --scott
--
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