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Well, yeah, again, electric shocks from mics !!

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Re: Well, yeah, again, electric shocks from mics !!

Postby Raphbass » Mon Jul 30, 2012 12:30 am

Had a reply from the venue - apparently no fault with their sockets. I'm not going to bother asking what exactly they tested but will take their word for it. I could maybe get my stuff tested again or just leave it at that.

The guitarist is a sort of "rocker" type, very nice guy but exudes the vibe that he won't remain that way if riled - he insisted on the day that his amp was fine and who am I to suggest otherwise.

So the mystery remains - an AC voltage between two supposed earths, cured by plugging into the same wall socket. Weird.
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Re: Well, yeah, again, electric shocks from mics !!

Postby seablade » Mon Jul 30, 2012 2:27 am

Raphbass wrote:Had a reply from the venue - apparently no fault with their sockets. I'm not going to bother asking what exactly they tested but will take their word for it. I could maybe get my stuff tested again or just leave it at that.

The guitarist is a sort of "rocker" type, very nice guy but exudes the vibe that he won't remain that way if riled - he insisted on the day that his amp was fine and who am I to suggest otherwise.

So the mystery remains - an AC voltage between two supposed earths, cured by plugging into the same wall socket. Weird.

I would strongly suggest if you work with that guitarist again, taking a look at the ground and making sure it is properly connected all the way through, and making sure you check the venue wiring yourself if you are ever there again. A 3 prong outlet tester at a minimum, but doing a full check with a multimeter isn't a bad idea, since you will want that to ensure ground continuity as well.

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Re: Well, yeah, again, electric shocks from mics !!

Postby Hugh Robjohns » Mon Jul 30, 2012 10:37 am

Raphbass wrote:The guitarist is a sort of "rocker" type, very nice guy but exudes the vibe that he won't remain that way if riled - he insisted on the day that his amp was fine and who am I to suggest otherwise.

Potentially the bloke that might save his life!

So the mystery remains - an AC voltage between two supposed earths, cured by plugging into the same wall socket. Weird.

Not weird, dangerous, and still in need of resolution.

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Re: Well, yeah, again, electric shocks from mics !!

Postby Raphbass » Mon Jul 30, 2012 7:44 pm

Well - there was also the issue that there was no problem when he plugged into the same circuit as us. If his amp's casing/earth were live it would still be giving us shocks regardless which circuit it was on.

Sounds like the same issue as the OP - cured when everybody goes into the same socket. Trouble is, what I didn't mention is we blew the fuse at the end of one tune - you know, Standard 12/8 Blues Ending no.2 - "da, da-da, da-da, da-da, da-da .(drum fill) . da, POP!" - only cymbals ringing and an uncertain sax note hanging on, and of course darkness as the lights went out (LEDS, 100W total at the most so can't be blamed).

Next time two extensions, even if going from adjacent sockets.

The operations manager at the venue just said briefly "no fault was found". I don't know what else I can do, I'm responsible for my gear, he's responsible for his hotel.
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Re: Well, yeah, again, electric shocks from mics !!

Postby seablade » Mon Jul 30, 2012 11:45 pm

Raphbass wrote:Well - there was also the issue that there was no problem when he plugged into the same circuit as us. If his amp's casing/earth were live it would still be giving us shocks regardless which circuit it was on.

No it wouldn't. If the ground is correct and the case becomes live due to a fault in the amp, it drains to ground through the ground wire, not through the person to ground.

NOTE: There are TWO seperate faults in this type of situation. And either without the other won't show symptoms.


The operations manager at the venue just said briefly "no fault was found". I don't know what else I can do, I'm responsible for my gear, he's responsible for his hotel.

You are responsible for safety as well in operation of your equipment. If you go back to the venue you really should consider it your responsibility to make sure that what you are plugging into is in fact safe. Again a 3 prong tester at a minimum, but a multimeter to test not only the socket but also the amp and kill two birds with one stone.

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Re: Well, yeah, again, electric shocks from mics !!

Postby Raphbass » Tue Jul 31, 2012 10:40 am

Yes - if I do another gig at that venue, knowing I've had a problem in the past, I would see it as my responsibility, not to mention self-interest, to check everything including their sockets.

Meanwhile though, if someone at the venue gets electrocuted and they look at emails mentioning the issue, my email might be part of the evidence but I can't imagine they'll come after me as being responsible by negligence.

If you warn someone there's a frayed brake hose on their car and they say "no it's fine" and drive off, I doubt very much you could be sued for their subsequent death.

By the way - what is an acceptable resistance between the AC plug earth and the ground pin at the end of the mic lead?

I just pulled out a random mic lead and it's about 0.8ohms, but from AC plug through the mixer to mic lead it's around 3ohms. Is this normal?
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Re: Well, yeah, again, electric shocks from mics !!

Postby seablade » Tue Jul 31, 2012 12:18 pm

Raphbass wrote:
Meanwhile though, if someone at the venue gets electrocuted and they look at emails mentioning the issue, my email might be part of the evidence but I can't imagine they'll come after me as being responsible by negligence.

If you warn someone there's a frayed brake hose on their car and they say "no it's fine" and drive off, I doubt very much you could be sued for their subsequent death.

No in that case you have done what you can I agree. It is not your responsibility to go in and check everything for them when you are not there so long as you have notified them. Then it becomes their responsibility to ensure their venue is safe.


By the way - what is an acceptable resistance between the AC plug earth and the ground pin at the end of the mic lead?

I just pulled out a random mic lead and it's about 0.8ohms, but from AC plug through the mixer to mic lead it's around 3ohms. Is this normal?

Both of those should be fine, however it is far more important the resistance between AC ground and the chassis of the equipment, not the ground of the mic cable. In general both of these will be connected yes, but it doesn't always happen, and is possible for the ac ground and signal ground to be connected without either going to the chassis which is still an issue.

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Re: Well, yeah, again, electric shocks from mics !!

Postby Raphbass » Tue Jul 31, 2012 12:51 pm

Just wiggling the mains connector in the IEC socket at the back of the mixer has achieved a reliable 1.2 ohms now, from the AC plug earth to the mic lead and to the casing. Maybe a bit of switch cleaner on contacts would be in order.

When I next play with the same guitarist should I check continuity of his AC earth to the guitar bridge? I'll probably be doing it under a stony scowl!
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Re: Well, yeah, again, electric shocks from mics !!

Postby seablade » Tue Jul 31, 2012 1:30 pm

Raphbass wrote:
When I next play with the same guitarist should I check continuity of his AC earth to the guitar bridge? I'll probably be doing it under a stony scowl!

AC Earth to the interior chassis of the amp itself. Remember, the AC earth is there as a safety against a fault of the amp taking the chassis live, which the electricity will then try to find the nearest path to ground. If the AC earth is not there, then there is no path to ground and noone gets hurt, until it is provided through a human being. The most common way this happens is a guitarist that is plugged into this amp that the chassis is now live on, places his fingers on the strings of his guitar and then steps up to a microphone connected to a properly grounded audio system. He has then provided a closed path to ground, through himself, to the audio system's AC ground, and this is how very bad things happen and guitarists get killed, but not the only way. Another way I have heard happening is the guitarist has a momentary contact with a grounded part of the building, for instance a radiator (Metal piping is usually grounded in buildings) while touching his strings which also completes the circuit.

Obviously you have to check to an area of the amp that is actually conductive, so look around the inputs especially for some steel. From what I have heard, I imagine all of this is part of the standard PAT test that must be done on your side of the pond on occasion, so I would look at the regulations for that for a good starting point as well (But hope someone on that side of the pond will come in to clarify, confirm, or correct me on that point).

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Re: Well, yeah, again, electric shocks from mics !!

Postby Hugh Robjohns » Tue Jul 31, 2012 1:34 pm

Yes.

And if he scowls ask him whether he values his life or not?

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Re: Well, yeah, again, electric shocks from mics !!

Postby dubbmann » Tue Jul 31, 2012 6:15 pm

hi all,
.
forgive if this q has been asked before but i don't understand if microphone shocks are a recurrent issue, why not switch to a wireless (battery powered) connection between mic and board? if the mic is not connected to an amp physically, it CAN NOT deliver a shock. break the metal connection, save the singer, it seems to me.

i also wonder if the same effect can be achieved using a wired mic going into an optical-transducer based compressor. not sure about that one.

anyway, thoughts?

d
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Re: Well, yeah, again, electric shocks from mics !!

Postby Hugh Robjohns » Tue Jul 31, 2012 7:12 pm

dubbmann wrote:why not switch to a wireless (battery powered) connection between mic and board?

Mainly because wireless mics are (a) a lot more expensive and need wireless receivers, (b) they are noisier and use companding systems which can mistrack in some situations and degrade the sound quality noticeably, and (c) are prone to interference, fading, glitching etc, and (d) licence-free channels are notoriously unreliable in busy parts of the country, (e) licensed channels add to the expense.

But if you are prepared to invest in high quality licensed radio mic systems and spend the effort installing proper RX aerials it is a good solution.

Proper equipment PAT tests and sensible grounding procedures work perfectly well though! ;)

i also wonder if the same effect can be achieved using a wired mic going into an optical-transducer based compressor. not sure about that one.

No. The attenuating element is a light-dependent resistor, but the signal isn't optically-coupled or isolated. Grounding issues would remain, I'm afraid.

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Re: Well, yeah, again, electric shocks from mics !!

Postby seablade » Tue Jul 31, 2012 11:56 pm

dubbmann wrote:hi all,
.
forgive if this q has been asked before but i don't understand if microphone shocks are a recurrent issue, why not switch to a wireless (battery powered) connection between mic and board? if the mic is not connected to an amp physically, it CAN NOT deliver a shock. break the metal connection, save the singer, it seems to me.

i also wonder if the same effect can be achieved using a wired mic going into an optical-transducer based compressor. not sure about that one.

anyway, thoughts?

d

I am surprised Hugh didn't answer the most obvious thing, because this merely hides a symptom, not solves the problem. If this happens you still have at least TWO safety failures (A failure in the amp and the removal of a path to ground) and it is more than possible to kill a guitarist by more ways than them stepping up to the microphone, it is just that is the most common symptom of this. As I mentioned above anything they touch that is properly grounded will injure if not kill them by completing the path to ground through their bodies.

Again FIX THE PROBLEM. Don't hide the symptoms.

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Re: Well, yeah, again, electric shocks from mics !!

Postby Sheriton » Thu Aug 02, 2012 12:50 pm

The title of this thread has been bugging me ever since its inception - as has been highlighted again and again, the mic is grounded and so is not causing the problem here. (Alright, in a small minority of cases it's possible that it could be a problem but the vast majority of cases involve a guitarist being at a high electrical potential because of a fault somewhere in their equipment and completing the circuit by touching the grounded mic.) Sorry Dubbmann but I'm right with Seablade here - sort out the underlying problem.
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Re: Well, yeah, again, electric shocks from mics !!

Postby seablade » Thu Aug 02, 2012 1:46 pm

Sheriton wrote:The title of this thread has been bugging me ever since its inception


When this thread was stickified, it was the second of two threads on the topic in a short period of time. The first would have been a much better thread to stickify at the time, but I am happy at least one of them did get stickied.

Yes the title of the thread is misleading, and if a mod cared to modify it I certainly won't complain, but what I think is good about the title is that it clearly says the symptom in it, which means many people will see it and recognize it as the problem before posting another thread on it. However as has been pointed out, the symptoms are not the cause and that can be confusing unless you read the thread.

In the end, we should probably type up a single long article on the topic that summarizes all the basic concepts of how this happens, and see if that can replace this thread as a sticky. That was people need to read one post instead of an entire thread to understand why the suggestion above wasn't really a good one(No offense intended). This post by the way is not one:)


...(Alright, in a small minority of cases it's possible that it could be a problem but the vast majority of cases involve a guitarist being at a high electrical potential because of a fault somewhere in their equipment and completing the circuit by touching the grounded mic.)...


I will also note that it isn't really just guitarists. When I started working full time in ministry, one of the first things I had to deal with was baptisms and how to mic those up. Obviously any electrical equipment near water is a touchy subject, but in the not to recent past before I came on there was a pastor that got electrocuted in the baptism pool when he reached up and grabbed a microphone to redirect it to him.

The first response of many people was along the lines of...

"That microphone had something called phantom power going to it, which when the pastor with his wet hands reached up to grab the mic, caused it to short circuit through his body, killing him."

As most people that understand how phantom power works would tell you, this is exceedingly unlikely and would generally require at least two body parts touching the microphone to even begin to contemplate, but even then is exceedingly unlikely. Much more likely would be that water gets inside the microphone, shorts out the microphone and destroys the microphone, long before anyone got injured.

Turns out what had happened is pretty much exactly what happens with guitarists. An AC ground was not connected. For guitarists, the reason we often see this is in some cases they will remove the AC ground to prevent a ground loop from ruining their sound, as often times people don't understand there are much safer ways to correct a ground loop, (Isolate the AUDIO ground instead of the AC ground). In the case of the baptismal however it was a much more basic issue.

Someone had built the water pump/heater at home and had not properly grounded it. In actuality what was happening was that every time that pastor stepped into the baptismal pool, they were stepping into an electrified pool of water. The issue was that electricity never had a path to ground so it did not endanger the pastor.... until he reached up and grabbed a path to ground, through the microphone into the properly designed and built sound system.

Let me repeat, in this case, just like in the case with guitars, the electrified problem already existed, electricity was going where it shouldn't have gone (The guitar amp, or the baptismal pool). The danger was that it also didn't have a SAFE path to ground (Water Pump/Heater was not properly grounded, Ground lead broken off Guitar Amp Plug, Ground Wire missing in Outlet, etc.) so it took the first path to ground it got, which in both of these cases tends to go through a human body.

Again there are at least two electrical faults occurring already in order for this to happen. First is that there is an internal fault causing the chassis to become electrified, and second is that there was no safe path to ground remaining that should have existed. At this point even if you could hide the symptoms, it is not very difficult for the electricity to take a different path to ground the next time someone touches something else that is grounded and the same result happens.

Seablade

EDIT:

This is why I WILL yell at you(Be you a professional or one of my students) if I ever see you use a 'cheater' plug (3-Wire to 2-Wire). You CAN use them correctly, most people do not. To use them correctly REQUIRES running a third wire between the cheater plug ground and a safe building ground. Guess what, you shouldn't EVER remove an AC ground.

And to be fair, it isn't just pastors or guitarists that cause this. I have literally walked into a venue while I was touring and been told I had to use cheater plugs on all my equipment or else I couldn't plug into the venue sound system(I wasn't touring with a large enough system for the venue at the time). This was by the supposed 'venue engineer'. Even after explaining, or trying to, what a ground loop was and the safe ways to address it they were insistent. I then proceeded to take the plugs, and conveniently 'forget' to plug in of my equipment in through the blasted things. Guess what, no ground loop. But the engineer was an idiot, and that combined with other reasons resulted in myself as TD and the stage manager calling the production company after the show and recommending they never go back to that venue again.

Even after the show went flawlessly with no hum or buzz the supposed 'engineer' still refused to listen to me when he noticed that his plugs were in a nice pile behind my sound board:)
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Re: Well, yeah, again, electric shocks from mics !!

Postby Raphbass » Thu Aug 02, 2012 6:08 pm

The average person identifies a symptom as a cause - "your mic is giving me electric shocks, there's something wrong with your mic."

Same as people will sometimes say "these speakers are making a funny noise". The answer is "well stop playing then". Sorry, a bit off-topic there!
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Re: Well, yeah, again, electric shocks from mics !!

Postby dubbmann » Thu Aug 02, 2012 9:54 pm

hi hugh and seablade,

your responses make complete sense. the fidelity issue is certainly a factor and, above all, i agree w/t point made by s/b that a wireless workaround would only hide the problem. i have dealt with floating ground issues before, and know the sad stories of the gtrists of the pretenders and renaissance who died from these so i don't take the issue lightly. i was just wondering off the top of my head about a wireless solution/workaround. seems it would but that wouldn't protect the band or the crew, just the singer. and i don't sing, so that hardly matters ;-)

it would be great if SoS published a one page "how to" on using a volt-meter to check out a venue's power "rectitude" (DC power joke inserted here) but it might be academic to most bands due to the constraints of playing live ("ya wanna play or dontcha?"). i had a house that had a floating ground problem, probably due to a settling water-pipe that had been used to ground the circuit and the connection had broken, and it was a nightmare. i blew up some good gear there =:-O

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Re: Well, yeah, again, electric shocks from mics !!

Postby dubbmann » Thu Aug 02, 2012 9:58 pm

seablade wrote:

This is why I WILL yell at you(Be you a professional or one of my students) if I ever see you use a 'cheater' plug (3-Wire to 2-Wire). You CAN use them correctly, most people do not. To use them correctly REQUIRES running a third wire between the cheater plug ground and a safe building ground. Guess what, you shouldn't EVER remove an AC ground.

And to be fair, it isn't just pastors or guitarists that cause this. I have literally walked into a venue while I was touring and been told I had to use cheater plugs on all my equipment or else I couldn't plug into the venue sound system(I wasn't touring with a large enough system for the venue at the time). This was by the supposed 'venue engineer'. Even after explaining, or trying to, what a ground loop was and the safe ways to address it they were insistent. I then proceeded to take the plugs, and conveniently 'forget' to plug in of my equipment in through the blasted things. Guess what, no ground loop. But the engineer was an idiot, and that combined with other reasons resulted in myself as TD and the stage manager calling the production company after the show and recommending they never go back to that venue again.

Even after the show went flawlessly with no hum or buzz the supposed 'engineer' still refused to listen to me when he noticed that his plugs were in a nice pile behind my sound board:)

seablade,

+1. in my circles, "cheater plugs" are called "widow-makers" (a hat-tip to the late, great, oh-so-missed robert calvert on that one) for obvious reasons.

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Re: Well, yeah, again, electric shocks from mics !!

Postby CS70 » Sat Apr 06, 2013 9:59 am

Hugh Robjohns wrote:

If you're lucky it will just tingle unpleasantly. If you're unlucky there'll be a bang and the gig will come to a premature end... as will the person who formed the link in the circuit.


Best piece of advice ever. Just read your piece at http://www.performing-musician.com/pm/nov07/articles/techspe..., great stuff.

Thanks!
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Re: Well, yeah, again, electric shocks from mics !!

Postby JonSSH » Sun Apr 14, 2013 2:52 pm

static shocks are very unpleasant and can give you quite a fright. BBC TV centre is famous for them and doing "later with Jools' it could often be a problem. However they are a discharge.. they will dissipate and once you have had a shock you will not get one straight away again until you have built up a charge...
Repeating shocks are a voltage/fault problem.
I always meter between mic and guitar strings...
I also always try the mic with the back of my hand. If there is a large voltage present your hand will form a fist and instead of grabbing the mic it will be forced away potentially saving your life...

Please people learn about power and don't take risks... don't take off mains earth leads! Buy a meter! Look at yourt plugs every now and again... check that the leads are secure inside...

Buy a Martindale mains tester and leave it in a socket of your plug board always...
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