Hi everyone !!
Ok, if you are interested(and it is, i'm advising to read through it, plenty of good info) i've posted this discussion before on 24/08/07 ''Electric shock from mic while touching guitar, ......''
I just came across the same problem a while ago, last week !!
My mixer was plugged in to a socket in the wall, so as musicians, but spread in different corners, different sockets (all on the walls).
And, to stop the mic from being electically charged, all i had to do was: Plug out my mixer which was going to a socket in the wall, and in the same socket (on the wall) i plugged in an extention lead, and then i plugged in the mixer in the extention+vocalists guitar ?!
Sounds strange to me but it worked !!
Could anyone explain to me (and to all of us) why did it work ?!
I just can't understand it !! Lost !!
Thanks guys !!

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Don't blame the world
Find a solution !!

Assuming the guitar amp was properly earthed, then by plugging the guitar amp into the same mains extension as the mixer, you ensured their earths were at the same potential, and thus no shocks.

I suspect the socket that the guitarist was using originally had no earth, or a very poor earth.

There really is no excuse these days for not checking each and every mains socket used in every venue with a simple socket tester to make sure they are wired correctly and are safe to use.

It is also a much better idea to run everything from the same socket or adjacent sockets, to reduce the risk.

Hugh

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Technical Editor, Sound On Sound

Call me extremely pedantic...

It's very rare that a mic will ever give you an electric shock. It's almost always the fault of the guitar / amp; it's only by touching the earthed mic that this becomes apparent. It always winds me up when people blame the mics rather than the true cause...

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There's nothing we can't face... Except for bunnies

i dont think it has anything to do with the amp.
i played at the colston hall in bristol and i even had problems there, and my equipment is certainly earthed!
It was that our amps were plugged in to a different circuit to the mixing desk

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Live Sound and Studio Engineer

Quote Paul Supersonix Studios:

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i dont think it has anything to do with the amp.

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To be fair, it is most usually a problem associated with a disconnected earth on guitar amps (to kill the hum, man!).

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my equipment is certainly earthed!

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I'm glad to hear it, but can you be as certain that the socket you plugged it into is properly earthed, or that the equipment, sockets, mains cables and plugboards that everyone else uses are properly earthed?

The only way to be sure and safe is to test the mains sockets you plan to use before using them, and check that everyone's equipment is earthed correctly before allowing them to plug anything in.

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It was that our amps were plugged in to a different circuit to the mixing desk

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Then there was a potentially lethal fault somewhere in that building. The difference in earth potential between sockets should be no more than a volt or two at most. To feel a shock when touching an earthed mic suggests that an earth was missing from the singing guitarist's rig. If that's the case, then he is playing on borrowed time....

Hugh

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Technical Editor, Sound On Sound

yeah well as hundreds of professional touring chart topping artists play there every year you would have thought that it would be properly earthed? maybe not,
the reason i said it wasn't the guitar amp was because i was getting shocks(and i play bass and sing) and so was our guitarist(who also sings) and its never happened before?

Edited by Paul Supersonix Studios (06/02/08 12:59 PM)

Quote Paul Supersonix Studios:

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yeah well as hundreds of professional touring chart topping artists play there every year you would have thought that it would be properly earthed? maybe not,

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The first rule of not dying is to not make assumptions like that. Faults happen. Things can change. When we rigged for some SOS seminars at the old Wembley Arena site, I found four faulty sockets in the same conference room -- a room that was used everyday by all and sundry. One socket had no earth, two were live-neutral reversed, and one just had no power. It happens! Often, the screws clamping the cables inside work lose or tarniosh and oxidise. Sometimes they weren't done up tight in the firtst place, and as the cable oxidises the connection goes high-resistance. That's all that's needed to make the safety earth next to useless! Sometimes someone else has had a major fault and the cable or the socket has been damaged but not reported to be fixed. Hence my advice to check them before using them.

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the reason i said it wasn't the guitar amp was because i was getting shocks(and i play bass and sing) and so was our guitarist(who also sings) and its never happened before?

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Were both your amps plugged into the same mains extension plug board by any chance? Or the same wall socket? If so, you've probably just identified where the missing earth was.

Clearly, there was a serious and potentially fatal fault somewhere. It could have been the earths protecting the sound desk, or it could have been the earths protecting the guitar and bass amps.

In my experience, shocks when touching a microphone are almost always because the mic body is properly earthed but the guitar amp's earth is disconnected, so that the 'earthed' metalwork on the amp (and guitar string earthing) floats up to half mains voltage (115V).

You won't feel that while playing as long as you don't touch anything else earthed, but the moment you do, you'll get the shock.

Now the missing earth might not be because the safety earths in the amps have been deliberately disconnected -- it could just as easily be because a mains cable or extension board has been damaged, or the wall socket could be faulty, as I've explaiend.

It's a less common scenario, but certainly still one worth investigating, that it could equally have been the other way around -- the guitar amps were properly earthed and it as the mixing console earth that was at fault. In that case, the mic's body would have floated to 115V, but you would have got the same tingle effect through the grounded strings.

Sadly, without all the same equipment set up in the same room in the same way, we'll only ever be guessing what the actual problem was. But it would be foolish to dismiss it and not check everything you can carefully.

As I said, the location of that discontinuous earth (or earths -- there could be more than one fault here) could be at any of a variety of places. The wall sockets, the extension cables, the mains plugs, the mains cables, the pluig-boards, or inside the equipment itself. The only way to be sure is to check every single mains cable you used, every extension cable, and every piece of equipment.

In fact, this really is something you should do regularly anyway. Cables get snagged and cut, or tripped over pulling the wires from the plugs, and screw connections inside plugs can work loose and wires corrode and oxidise.

If they all check out okay, then it was probably the mains sockets in the venue -- it really isn't that uncommon! Buy a tester, and make a point of using it next time. it only take a few seconds. Also, to be almost completely safe, make sure you run all your own equipment through an RCD, and persaude all the others in the band (and FOH) to use RCDs too.

Hugh

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Technical Editor, Sound On Sound

ok thanks hugh that makes a bit more sense now, it was a while ago so cant exactly remember where we were plugged in to but yeah i always use RCD's now.

it only happened when we sang and touched our strings.
Cheers

Edited by Paul Supersonix Studios (06/02/08 02:15 PM)

Quote Paul Supersonix Studios:

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it only happened when we sang and touched our strings.

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Yes, it would.

Normally, the strings are earthed through the guitar cable's screen to the guitar amp, and from their to the mains safety earth of the amp's mains lead.

The mic body is earthed through the mic cable screen to the mixer, and from there to the mains safety earth of the mixer's mains lead.

If one or other of those mains safety earths becomes high resistance or disconnected, then the mains input filtering of the amp or mixer will tend to pull everything connected to the now disconnected earth line up to half mains volts (115V in the UK and Europe).

If you are playing the guitar while touching the mic body as you sing, you complete a circuit, one side of which is earthed, and the other is sitting at 115V. it doesn't matter which way around it is -- which side is still earthed and which is floating -- the results ae the same.

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.

You said this only affected you and the guitarist, and that's often the case. Vocalists generally only touch the mic and nothing else -- so there is no circuit. Likewise keyboard players generally only touch plastic keys, so there's still no circuit.

The worst case scenario is when the circuit is formed across the hands -- one hand on the guitar strings, the other on the mic. That way any current flow is straight across the chest, through the heart, and is likely to stop the heart. One ex guitarist...

Hugh

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Technical Editor, Sound On Sound

never happened to me b 4 but thanx 4 posting that thread...
it's gonna save me loads of time in the future...cause i'm sure it'll happen

Quote Paul Supersonix Studios:

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i played at the colston hall in bristol and i even had problems there, and my equipment is certainly earthed!
It was that our amps were plugged in to a different circuit to the mixing desk

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I could tell you a few stories about that venue, but probably had better not.

Most touring acts will plug distro into the heavy stage power tie stage right (good for 400A or so IIRC) and forgo the use of the random 13A points except for back stage tea and coffee.

That the earthing is a little suspect comes as no surprise (No reflection on the house crew, council run venue and Bristol council, well 'nuff said).

I would heavily advocate always testing before you plug in anywhere, in any venue and that the use of RCD protection on backline supplies is just good sense (along with FOH if you don't trust things).

Note that most simple socket testers cannot identify a neutral/earth reverse.

There are a scary number of dodgy sockets out there, test everything and be paranoid, it's good for you.

Incidentally, IME CEE form sockets are less likely to be miswired as people pay more attention to the 'industrial' power then they do to the domestic stuff (Good reason to use them if available).

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

the engineer was a right pr*ck he just said "deal with it". in the end our guitarist just got so annoyed at the end of the set just smashed over the mic stand lol

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Live Sound and Studio Engineer

Hehe my guitarist was getting static off his guitar in band practice dont know why it happend, he was also using a mic at the time and quite close to the amp and socket. It was amusing to watch when now and again hed jump in the middle of a song with a small yelp!

haha yeah its not fun if your being shocked after a 30 minute set my mouth was burning.

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Live Sound and Studio Engineer

Quote Paul Supersonix Studios:

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the engineer was a right pr*ck he just said "deal with it". in the end our guitarist just got so annoyed at the end of the set just smashed over the mic stand lol

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You are completely within your right to walk out there.

NOTHING is worth the risk you just put yourself through(30 minutes???!!!!). If they have a problem with you walking out, tell them you will feel happy to have the local inspector come in and make sure the building is up to code and if that is the case you will come back. But until then something is very much NOT right there and they are endangering lives like that. Honestly the engineer that says, deal with it, to something like that needs to be fired on the spot. Maybe then he will learn not to screw with electrocuting people.

Seablade

NOTE: I am in the US, though I would imagine a similar safety inspection exists in the EU for such situations.

City council venue Seablade, the place (a ~1,800 seat somewhat run down neoclassical pile last time I was there) is owned by the AHJ! I understand that they have done some work on it in the interim, but the real plan for as long as I can remember has been to replace it.

This is the council which owns another venue where you always had to ensure a lantern was plugged into the first socket on the FOH bar and securely clamped to the bar as that was the only one with the earth connected (Lots of moaning from us, zero action from the council, and this is in 240/415V land)! Mind you, they also supplied me a 'street lighting technician' to fill a rider requiring the venue to provide a 'lighting technician', nice guy, but about as useful as a chocolate fireguard.

I do wonder if that 'engineer' was actually a hired in PA company as I don't recall that place having any PA worthy of the name (And from what I recall of working there a few times, that does not sound like behaviour the resident chief would have accepted from his people).

It does however sound like the sort of thing a pissed off third party sound provider might perpetrate after a bad day.

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

Quote DingoDave:

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Hehe my guitarist was getting static off his guitar in band practice dont know why it happend

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Not being funny here, mate, but you are dismissing a seriously life-threatening situation here. You need to find out why it happened. Something is UNSAFE in your rig.

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It was amusing to watch when now and again hed jump in the middle of a song with a small yelp!

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I wonder how many people will laugh when your mate -- OR YOU -- DIE!

This is serious and it happens everyday. And if something nasty does happen, and it can be shown that you were aware of the fault but did nothing to rectify the problem, it won't do you much good either!

Seriously -- sort this out NOW. Get the gear checked. Get the room wiring checked.

Hugh

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Technical Editor, Sound On Sound

I know it's been said a million times before, but surely we can all agree that this topic warrants being made a sticky.

Also, Dan/Hugh/anyone, do you have a particular socket tester that you recommend? I know for a fact that my rather basic Maplins jobby (the name of which completely escapes me) will spot a disconnected earth, but won't pick up on a reversed live/neutral. Dan, I think I've heard you talk about stuff Martindale(?) before now?

Quote dmills:

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City council venue Seablade, the place (a ~1,800 seat somewhat run down neoclassical pile last time I was there) is owned by the AHJ! I understand that they have done some work on it in the interim, but the real plan for as long as I can remember has been to replace it.

This is the council which owns another venue where you always had to ensure a lantern was plugged into the first socket on the FOH bar and securely clamped to the bar as that was the only one with the earth connected (Lots of moaning from us, zero action from the council, and this is in 240/415V land)! Mind you, they also supplied me a 'street lighting technician' to fill a rider requiring the venue to provide a 'lighting technician', nice guy, but about as useful as a chocolate fireguard.

I do wonder if that 'engineer' was actually a hired in PA company as I don't recall that place having any PA worthy of the name (And from what I recall of working there a few times, that does not sound like behaviour the resident chief would have accepted from his people).

It does however sound like the sort of thing a pissed off third party sound provider might perpetrate after a bad day.

Regards, Dan.

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Again, yank over here sadly, but I would say then the next step is to take it over the city. At least in the US this would violate NATIONAL safety standards, so there is nothing stopping someone above the city from shutting it down if need be. Again I would venture a guess in the EU that a similar situation exists.

I know it sucks, but honestly they need to be forced to do something. This is waiting for someone to die as described right now. No hyperbole at all, it literally is a matter of waiting till the first person dies before anything is done unless someone goes over their heads if the city is unwilling to do anything with it.

Honestly, there have been venues I have told production companies never to book again as they were dangerous along this level. This would certainly qualify, step one is to never play it again, and make sure noone you know plays it until they get this fixed. Step 2 would be to report it over the heads of the city IMO.

Seablade

Quote Matt P:

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I know it's been said a million times before, but surely we can all agree that this topic warrants being made a sticky.

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Yea at this rate, I gotta agree, something needs to be done to keep this perfectly visible, not sure if a sticky thread is the right answer or not. Maybe an FAQ section along the lines of Martin's computer FAQs? Ah well up for the mods/admins to decide not me.

Anyways to answer your other question I bought this kit for basic electrical analysis that I carry with me.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=205783-7 2068-TK-30&lpage=none

I believe the socket tester in it wil check for a live/neutral reverse, but I will double check tomorrow. At the moment I need to get some sleep and don't feel like getting dressed to go out to the car to check.

Seablade

when i have this problem i use a multimeter and the odd radiator to find which earth is bad and then i put a sticker on it saying "Faulty. This is not to be used until repaired" then i tell the venue management what i've done and suggest that it's repaired. If i'm feeling really bolshy i'll follow it up and report them to the local coucil, their licensing authority or HSE if the sticker was removed without being rectified (i have done this to a council venue whose 63Amp supply was LN reversed).

if you knew what you were doing and if you had the appropriate test gear, you could measure between the earth connections on the stage and mixer supply sockets and see if there is a voltage -more than 5 volts or so suggests a possible problem, double figures means a definite issue with earthing in the building. i have found over a 120 volts on an earth in a leisure complex venue.

a missing or dodgy earth is potentially lethal should a fault condition occur, and the venue would be fined heavily or shut down once HSE had been in there should there be an accident (happened to a franchise of a food chain in my home town after a lethal shock).

also any venue needs an annual electrical inpection to get their PEL, so it would be good to ask for a copy of the report for this "council-run" venue -i think as a council they are obliged to supply one to a formal request. stir up some mud, you might get things to happen before someone dies.

that aside, the usual reason for shocks on microphones is a removed earth on guitar amp plugs -in this case it could be a bad earth from either side from the mains sockets.

anybody who lives in Bristol fancy verifying this? it does sound like something does need to be done.

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planet nine
lincoln, uk.

Thanks to previous SoS threads on this, I now always bring my 'Martindale socket tester' to everygig,
and fit a couple of Wickes RCDs onto the bands' gear.

Occasionally they trip out in the middle of songs, so the band can be a little "auch! not that bloody thing that ruins our gigs!" but I just keep reminding them that leaving the stage in an ambulance would ruin the gig even more.

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

find an electrician friend to measure your gears leakage current feline -most PAT testing gear will do this -see if you have some borderline equipment or if you have any congealed beer in any of your socket strips...

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planet nine
lincoln, uk.

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I do wonder if that 'engineer' was actually a hired in PA company as I don't recall that place having any PA worthy of the name (And from what I recall of working there a few times, that does not sound like behaviour the resident chief would have accepted from his people).

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nah it was the inhouse lampy i think. they have some sort of turbosound rig in there, not very good though.

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Live Sound and Studio Engineer

Quote Nathan:

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find an electrician friend to measure your gears leakage current feline -most PAT testing gear will do this -see if you have some borderline equipment or if you have any congealed beer in any of your socket strips...

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nah, the time it tripped, there was spilt beer about an inch deep all over the stage and the 4-ways, so "go figure", etc etc...

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~~~ A weasel hath not such a deal of spleen as you are tossed with! www.feline1.co.uk ~~~

heh, no argument

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planet nine
lincoln, uk.

Quote Nathan:

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also any venue needs an annual electrical inpection to get their PEL, so it would be good to ask for a copy of the report for this "council-run" venue -i think as a council they are obliged to supply one to a formal request

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Yep - with very few exceptions, under Freedom of Information they are required to supply any document held by the public authority.

The request for information must be somehow written down (email considered fine) but technically doesn't have to be in any way "formal".

You don't have to live in bristol - anyone should be able to email: foi at bristol.gov.uk and ask for a copy of the report....

As this is a topic that comes up regularly, and is 'mission critical' I have made it a sticky as suggested.

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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As this is a topic that omes up regularly, and is 'mission critical' I have made it a sticky as suggested.

hugh

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Applause!
Righto, is there prize for writing the best definitive Electrical Safety guide?

Hi all,
At the weekend I was getting small shocks from the main vocal mic (our singer doesn't play any instruments or have anything plugged into mains). There was no unecessary phantom power and the problem was only on the main vocal. I was splitting it into 2 channels and using 1 to drive monitors... could it have been something in the desk? Anyone got any ideas how this can be fixed if i encounter it again?
Cheers
Pete

Tried to search in this thread about it, but i was surprised to see that noone came with the suggestion to put a DI between the amp and the guitar to prevent shocks.
Of course you have to plug the DI into the mixer or remotebox on the stage, just to even out the differences in current between different outlets. But with that done, you won't have any problem with shocks while grabbing your guitar and singing.

Best regards
Sylvester

That won't fix any problems with earthing on the mains sockets, though...

You could still injure/kill yourself.

Although, on the bright side, that annoying hum will have been stopped...

Dodgy socket wiring would be my bet for the shocks from the (non guitarist) vocal mic.
Get a simple three lamp socket tester, and use it every time, you will find some amazing things.

On the subject of guitars, I have one that has had a low value class Y cap added in series with the lead that connects the bridge to the screen.
It has little effect on the screening, but means that the path to the amp will be too high impedance to deliver a belt that is likely to be fatal (Cheap insurance, and I commend this modification to the house).

Not of course that this makes lifting the safety ground safe, but it does provide some protection against muppetry.

Regards, Dan.

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Audiophiles use phono leads because they are unbalanced people!

Quote dmills:

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Not of course that this makes lifting the safety ground safe, but it does provide some protection against muppetry.

Regards, Dan.

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LOL.
Good one.
Should be in 'Top Tips'.

Cheers Dan,
I'm not totally sure what you mean by the socket tester.. the only power she could have been connected to was from FOH.. on it's own feed from the distro... maybe test that output? I don't get how we didn't encounter the same problem with other (vocal) mics.
Cheers
Pete

Quote PeteJ:

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At the weekend I was getting small shocks from the main vocal mic (our singer doesn't play any instruments or have anything plugged into mains).

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By small shocks, do you mean static 'zaps' -- short, sharp zaps that are not continuous -- or do you mean half mains voltage continuous electric shocks?

The former is caused by clothing or flooring, generally and isn't lethal but can be startling. The latter is potentially lethal...

I'm ubnclear when you say you got shocks but the singer doesn't play anything. Was the singer getting shocks too?

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There was no unecessary phantom power

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Phantom power is DC and low voltage, so it's not a factor in this.

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and the problem was only on the main vocal.

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That is very odd... and quite unlikely if it is real faulty-earth style electric shocks! But could be possible if it was static shocks.

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I was splitting it into 2 channels and using 1 to drive monitors... could it have been something in the desk?

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Do you mean two channels of the same desk, or split to two different desks?

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Anyone got any ideas how this can be fixed if i encounter it again?

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Check all the mains earths on all the equipment, mains leads, and distro boards. Check the wall sockets at the venue before using them. And power eveything via RCDs.

hugh


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Technical Editor, Sound On Sound

Thanks Hugh...
Static shocks I reckon. Sorry about the confusing bits.. I just mix the band so when I said myself and the singer it was me during soundcheck and her during the show. Maybe it was floor / clothing related.. I'll check out what she's wearing next time. Any other ways of minimizing this? Changing cables / stands / mics?
The channel thing was just that I had to mix mons + foh from the same board so I y-split the main vocal into 2 channels of the same desk - then used one for out-front and one to send to monitors with different eq.
Thanks for your help..
best
Pete

Quote PeteJ:

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Static shocks I reckon.

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Yes, sounds more likely.

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I'll check out what she's wearing next time. Any other ways of minimizing this?

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Can't do anything with the mics/stands etc. They have to be earthed for safety. Best to check your lady singer for static-inducing underwear before every gig

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Best to check your lady singer for static-inducing underwear before every gig

hugh

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You could always attach some of those static tails you used to see under the rear bumpers of cars in the 80's.

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Best to check your lady singer for static-inducing underwear before every gig

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Something I've made a point of for years. Sometimes a visual check alone is not enough, as you're doubtless well aware. However, no matter how the check is carried out, I find the best option is to ensure it's removed, and held in safe keeping pending further investigation.

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