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

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

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.

Ignore Phil. He hasn't had his morning bowl of medication for his mental problems.

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!

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

Before doing the above, touch the guitar strings to the microphone. A guitarist I know was in the habit of doing that, and one day a GFCI tripped during sound check.

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

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

This may or not be true but can often happen. Generally speaking as Scott notes the danger from gear on stage comes from improper grounding. The use of clipped "ground buster" plugs and the rest is a huge No-No. The whole idea of proper grounds is that IF rain causes a short to say the mic stand, the fact that it is grounded will simply blow the fuse rather than kill someone.

BUT the catch is that mics and sound systems are very prone to hum. And soundmen tend to take a quick and easy approach to hum reduction. "ground busting" is one such approach. Some gear even has ground-lift switches built in! All this can work fine if you "bust" signal ground and not safety ground. But obviously the potential for mistakes can be great!

As for the above comments, they make sense too. Dig. A singer typically also plays a guitar. The guitar plugs into an amp (often "vintage" of unsafe design) on stage. The mic on the other hand is feeding some professional gear run (presumably) by a pro. The likelihood of the mic stand being soundly grounded is great. Thus, if the guitar amp due to rain or other factors develops a voltage with respect to earth ground, the guitar player touching the mic will receive current not from the mic but from the faulty amp through his guitar which flows out through the soundly grounded mic. Since it is not common practice to run a heavy earth ground to the chassis of the guitar amp on stage, there is a great potential for such an accident!

Well, one of the first and most strict things I teach the soundguys that work my shows is electrical saftey IMO anyone who trys to cure a hum by defeating a saftey groung is simply a idiot, not a "soundguy" , soundguys KNOW better idiots dont

So IMO it may be symantics to you but your not a soundguy unless you understand the job of a soundguy and one of the most important aspects of that job is saftey and electrical saftey is lesson one

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

Exactly! I've worked around computers (not here in the USA) where a ground was not available (a "special" adapter was used to remove the ground... funny how those adapters are sold in stores), and it *hurts* when you touch the chassis. 220V, too. We learned very quickly to shut down the computers before plugging/unplugging devices, to avoid pain.

Even when plugging my laptop into the mains to charge it, I'd get an unpleasant shock if I even touched the ground around the microphone Line Out jack.

Oh, here in the USA, the government really CARES about us! haha

Michael

DC outlets? I've heard tell, but I've never actually seen one. Do you know if you can you still buy DC and steam in New York? DC is great for studios and theater because the lamps don't sing. The problem is, there isn't much other than old resistance dimmers that will work with DC. Have you seen it in other places?

David

Snipped drivel...

Use wireless devices. Doh!

Well, that pretty much rules out live stage performances in the rain with a wired mic, eh?

Jeez!

In the US, I've seen 2 types of adapters.

One has a 3 pronged outlet with a 2 prong plug and aw ground wire that is intended to be connected to the screw that holds the plate on. Assuming that there is a metal box, and it is grounded (big assumptions). If everything goes as to plan, the 3 pronged outlet should then be fine. The advantage of the wire is that you can use one in each outlet. Some people just cut off the wires and ignore the ground (bad plan).

The other style is the same thing except with a spade attached directly to the plug in such a position that it can be connected directly to the screw to provide a ground and it locks the adapter onto the outlet making it more stable. You can only use one on a duplex outlet.

If used correctly, these are fine tools, but using them to lift the ground is not allowed.

That isn't a situation that you should have to put up with. Typically a laptop floats and isn't directly connected to ground. There is probably something connected to it that isn't wired correctly, or has some other fault. A while back, the RF cable for the cable TV had quite a bit of kick when referenced to a water pipe ground. We have fiber running directly to the side of the house now. It is no longer an issue :-)

They try, but you have to remember that some of "us" are retailers and manufactures may have a different slant on what caring should be. Sometimes they have more pull than you or I.

David

"Christian Marg"

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

NYC still had DC mains available until about a decade ago, when Con Edison finally managed to install rectifier stacks running off three-phase at the last of the DC customers. Most of them were folks using DC for elevator service.

However, because of the leftover DC infrastructure, you will still see places with DC power panels, operated off a rectifier, and with outlets off the DC panel.

It still turns up in some larger cities with very old infrastructure. Here you're more likely to see DC elevator motors with a motor-generator set to provide the DC for them, but up in Richmond, VA. there is a church with a fancy speed control system on their organ that was originally hooked to DC mains and today is run off a rectifier stack. There are probably a lot of those around.

--scott

Its quite dangerous. I think Spinal Tap lost a couple of drummers to various electrocution incidents.

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

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