Quantcast
tired of getting shocked at gigs - Gearspace.com
The No.1 Website for Pro Audio
tired of getting shocked at gigs
Old 21st May 2007
  #1
Lives for gear
 
1 Review written
🎧 15 years
tired of getting shocked at gigs

from ground loops going between the vocal mic and guitar strings.

what can I do?? Is there a way to ground the guitar off of the strings? or to put a capacitor in the path to block dc voltage? or to do this in the mic cable? anything?? I thought mic transformers weren't able to pass dc....?

though my drummer gets a good laugh just from the look on my face every time it happens...
Old 21st May 2007
  #2
Lives for gear
 
Wavebourn's Avatar
 
🎧 15 years
Use your vocal and guitar gear properly grounded. There should be a safety ground connection from chassis of your gear to power outlet through 3-wire connections.

Also, when you are too close to mic it boosts lows and pops.
Old 21st May 2007 | Show parent
  #3
Gear Guru
 
tINY's Avatar
 
1 Review written
🎧 15 years


You need to make sure there are safety ground connections on your amp and your mic.....



-tINY

Old 21st May 2007 | Show parent
  #4
Lives for gear
 
code green's Avatar
 
🎧 15 years
oops

Last edited by code green; 21st May 2007 at 11:28 PM.. Reason: oops--doublepost
Old 21st May 2007 | Show parent
  #5
Lives for gear
 
code green's Avatar
 
🎧 15 years
just DON'T do this: "test" for shock by touching the mic with one hand, with the other hand on your guitar strings...that puts the path of the current right across your heart, and that's where the danger lies.stike

Last edited by code green; 21st May 2007 at 11:30 PM.. Reason: meant to use tut, tut smiley but accidentally gave the finger!
Old 22nd May 2007 | Show parent
  #6
Lives for gear
 
1 Review written
🎧 15 years
Quote:
Originally Posted by tINY ➑️


You need to make sure there are safety ground connections on your amp and your mic.....



-tINY


sorry for being dense, but what does this mean? and if the building the particular club I am playing in that night isn't grounded, or if the PA isn't grounded properly, will it even matter?
Old 22nd May 2007 | Show parent
  #7
Lives for gear
 
Berolzheimer's Avatar
 
🎧 15 years
Those things are all important but there's one other simple thing you can do, esp. when you don't have control over the grounding scheme.


Carry some foam windsceens with you & always put one over your vocal mic.

Easy.
Old 22nd May 2007 | Show parent
  #8
Lives for gear
 
1 Review written
🎧 15 years
uhh.....when was the last time you saw someone do this live at a gig? Part of the reason I bring my own mic is because I do like to get up on it...especially in quieter vocal parts where the guitars are still loud...and shouting and screaming don't really sound as intense without the proximity effect. i'm only half joking there.

really though, can someone please explain how DC voltage gets into a mic with an output transformer in the first place? And if there is anything I can do? I gig out quite a bit and there is really no way of knowing what you are gonna get until you get up on stage and start singing. I need to build in some sort of protection to my gear so that this doesn't ruin any more performances.

edit: ooohh, you mean foam windscreen like on a reporter's mic? would this work? I guess it would be a way of fixing this...not as geek as I was trying to get but it might work.
Old 22nd May 2007 | Show parent
  #9
Lives for gear
 
max cooper's Avatar
 
🎧 15 years
A guitar tech put EMG's on my live guitar and I never experienced the problem again.

Always carry your own vocal mic. Imagine the germs.

If you really want to avoid the shock, go wireless.
Old 22nd May 2007 | Show parent
  #10
Gear Guru
 
tINY's Avatar
 
1 Review written
🎧 15 years


stellar -

Does your amp even have a ground pin?

The other thing you can do is get a wireless transmitter......



-tINY

Old 22nd May 2007 | Show parent
  #11
Lives for gear
 
1 Review written
🎧 15 years
nice thoughts, guys....but EMG's just aint my thang. I am usually using either P-90s or Gibson PAF's.

not sure if the amp does have a ground pin...its a stock marshall that I use live...it does have a 3 prong plug. but who knows when you plug it in at a club if it is really grounded or not... or plugged into the same outlet as the PA....

I do always carry my own vocal mic, and I am a germ-a-phobe. In fact, I always ask permission from the sound guy before attempting to plug it in. The last guy I asked, "would it be okay if I use my own mic" replied, "I would recommend it. unless you want herpes." nice.

wireless aint gonna happen, though also not a bad idea. I dont think it fits with the 'image' of the band though.
Old 22nd May 2007 | Show parent
  #12
Lives for gear
 
JohnRoberts's Avatar
 
🎧 10 years
Assuming both the mixer and the guitar amp are OK and grounded, you may be seeing a problem with power ground quality (or lack therof). One obvious fix is to run an extension cord from stage to where the mixer the mic is coming from is plugged in, and plug them both into the same power.

JR
Old 22nd May 2007 | Show parent
  #13
SK1
Lives for gear
 
SK1's Avatar
 
🎧 15 years
Quote:
Originally Posted by stellar ➑️

...........
wireless aint gonna happen, though also not a bad idea. I dont think it fits with the 'image' of the band though.
I don't follow you ........ your not thinking about a wireless headset are you ????

I think he was saying just a regular old wireless shure 58. If it sits in a mic stand I don't see how it would mess with the band's image. Most fans wouldn't even notice.

Old 22nd May 2007 | Show parent
  #14
Lives for gear
 
A27Hull's Avatar
 
🎧 15 years
I'm an electronics noob...

If it is not static build up, what causes this?

How can a voltage exist across either guitar, or mic if it is not a static charge or a potential difference?

In improperly grounded situations, is it possible for voltage to drain back to the guitar from amp/back to the mic from a mixer--thereby accumulating at each end, only to spark when you (the conductor) complete the circuit?

Do performance cables wired from ground pin & the actual connector cause this more frequently?



The reason I say this is, having experienced this phenomenom in my own performance, the shock seems more like a static discharge than a continuous stream.
Old 22nd May 2007 | Show parent
  #15
Lives for gear
 
1 Review written
🎧 15 years
Quote:
Originally Posted by SK1 ➑️
I don't follow you ........ your not thinking about a wireless headset are you ????

I think he was saying just a regular old wireless shure 58. If it sits in a mic stand I don't see how it would mess with the band's image. Most fans wouldn't even notice.

yeah you're probably right.......

I guess I was hoping for a way to 'safeguard' this from happening in various situations.... usually its just 'set up and play'.
Old 22nd May 2007 | Show parent
  #16
Lives for gear
 
1 Review written
🎧 15 years
Quote:
Originally Posted by A27Hull ➑️
If it is not static build up, what causes this?

How can a voltage exist across either guitar, or mic if it is not a static charge or a potential difference?

In improperly grounded situations, is it possible for voltage to drain back to the guitar from amp/back to the mic from a mixer--thereby accumulating at each end, only to spark when you (the conductor) complete the circuit?

Do performance cables wired from ground pin & the actual connector cause this more frequently?



The reason I say this is, having experienced this phenomenom in my own performance, the shock seems more like a static discharge than a continuous stream.

You may be on to something there... now might also be a good time to ask how many volts are you getting whent his happens?
Old 22nd May 2007 | Show parent
  #17
Lives for gear
 
A27Hull's Avatar
 
🎧 15 years
well, as I said I'm a noob...just starting electronics tech school next week.

well, one things for certain, there has to be a small amount of current, maybe a few mA for you/me to get that uncomfortable shock

anything around 50mA would be a serious jolt (i.e. you'd drop your guitar, maybe spill your beer... ) and 100mA could cause death...(through chest cavity)--according to this self-learn book i'm reading.

depending on the resistance...volts could be high, and as far as I know the voltage is variable,

What is your body's resistance/or anyother resistance in the path?
Old 22nd May 2007 | Show parent
  #18
Led
Lives for gear
 
Led's Avatar
 
🎧 15 years
Also, what kind of shoes are you wearing when you gig? I have a few pairs of shoes, in particular the ones with a rubber sort of compressed foamy sole that create static shocks to just about anything metal including door handles.
Old 22nd May 2007
  #19
Lives for gear
 
Ike Zimbel's Avatar
 
🎧 10 years
Exclamation

1st of all it's AC voltage, not DC that you are most likely dealing with. 2nd, the voltage is not coming from the mic, it's going to the mic from your amp.
The mic, of necessity is grounded through the Pin-1 connection on the XLR, and has to stay that way or it will be very, very noisy. The amp should be grounded through the ground pin on the AC plug. If for some reason it is not making a connection there, it will be "looking" for a ground, in this case finding one through your lips.
Here's a few things you could and should do:
1) Make sure that you really do have an AC ground going to your amp. This means checking your whole set-up and making sure that the ground pin has not been broken off anywhere in the chain (like if your amp plug is definitely ok, but you plug into a power bar or extension cord that has a missing ground pin, you are still not grounded). If it is an older amp, or you purchased it used, have it checked by a reliable shop or tech (IOW, if it's new, it really should have the ground pin).
2) If the plug for you amp has ever been replaced with a DIY plug from a hardware store, MAKE SURE it is wired properly. It should be:
Green wire>Green Screw
White or Blue wire>Silver Screw
Black or Brown wire>Gold Screw
3) For less than $10.00 you can buy a simple ac tester from any hardware outlet. These are usually yellow or orange plugs with three lights in them. When you get the two clear lights on, the outlet you are checking is good. If you get a red light it's bad, and if you get only one or the other of the clear lights it's bad for different reasons (which are all explained on the side of the device). Once you have this use it to check an outlet before you plug in. That will answer the question about the state of the ac wiring in the club.
4) To safely test whether or not you are going to get a shock: Hold the neck of the guitar, with your thumb or other fingers making contact with the strings and then, WITH THE SAME HAND stretch out your little finger and touch the ball of the mic. If you don't get a shock, you are good. If you do, see the above, again. Good luck!

Old 22nd May 2007 | Show parent
  #20
Lives for gear
 
A27Hull's Avatar
 
🎧 15 years
Quote:
Originally Posted by Zapaudio ➑️
1st of all it's AC voltage, not DC that you are most likely dealing with. 2nd, the voltage is not coming from the mic, it's going to the mic from your amp.
The mic, of necessity is grounded through the Pin-1 connection on the XLR, and has to stay that way or it will be very, very noisy. The amp should be grounded through the ground pin on the AC plug. If for some reason it is not making a connection there, it will be "looking" for a ground, in this case finding one through your lips.
Thanks!!

But...amps are high power devices, pulling 11* volts from the wall, ramping it up within the amp..not to forget higher than 100mA worth o current, right?

you talking about voltage or current drain? to a ground that isn't there, but looking for one...

that seems like an awful lot of voltage/current at/within the amp to be simply feeling an incomfortable spark.

can you elaborate?
Old 22nd May 2007 | Show parent
  #21
Lives for gear
 
A27Hull's Avatar
 
🎧 15 years
Zap-

can one totally rule out static charges of potential difference between the guitar/mic?
Old 22nd May 2007 | Show parent
  #22
Gear Addict
 
CoteRotie's Avatar
 
🎧 15 years
Quote:
Originally Posted by Zapaudio ➑️
1st of all it's AC voltage, not DC that you are most likely dealing with. 2nd, the voltage is not coming from the mic, it's going to the mic from your amp.



[Snipped for brevity]

3) For less than $10.00 you can buy a simple ac tester from any hardware outlet. These are usually yellow or orange plugs with three lights in them. When you get the two clear lights on, the outlet you are checking is good. If you get a red light it's bad, and if you get only one or the other of the clear lights it's bad for different reasons (which are all explained on the side of the device). Once you have this use it to check an outlet before you plug in. That will answer the question about the state of the ac wiring in the club.
4) To safely test whether or not you are going to get a shock: Hold the neck of the guitar, with your thumb or other fingers making contact with the strings and then, WITH THE SAME HAND stretch out your little finger and touch the ball of the mic. If you don't get a shock, you are good. If you do, see the above, again. Good luck!
This post is exactly correct. Many times the issue is cause by EMI suppression capacitors in equipment with 3 prong plugs. These small value capacitors are placed between the AC conductors and ground (the third prong) to short out any high frequency noise from getting on to the power grid and therefore into every piece of audio and radio equipment in the place. They also allow a small amount of 60HZ AC leakage to the equipment's case ground. There are special safety-rated caps for this called Y-capacitors that you must use to meet IEC and UL regulations. The manufacturers assume that the third prong will be grounded, so the potential of the metal grounded pieces (guitar strings, TRS shields, etc.) will not rise above ground (or your mic's potential). When the third prong isn't properly grounded, you get a nasty tickle. The good news is that the value of the Y-caps is small enough that in general a dangerous level of current can't flow. If equipment is poorly or cheaply designed and a Y-cap fails shorted or something else "hot" shorts to the case THEN the ungrounded third prong can be harmful or fatal. Yet another reason to use quality equipment and carry an outlet tester.

To test for potentially fatal potential, touch the guitar strings to the mic before grabbing both. If the strings evaporate in a shower of sparks you might want to check the wiring. And put new strings on.

Regards,

John
Old 22nd May 2007 | Show parent
  #23
Lives for gear
 
Wavebourn's Avatar
 
🎧 15 years
Quote:
Originally Posted by A27Hull ➑️
well, one things for certain, there has to be a small amount of current, maybe a few mA for you/me to get that uncomfortable shock

4 mA would be plenty...

Most probably you had 60V through RFI filter capacitors. Not enough to kill, but sensible enough to understand that something is not very right.
Old 22nd May 2007 | Show parent
  #24
Gear Guru
This thread is like that commercial when the guy is choking and everyone stands around discussing the situation until some guy walks up and does the Himlick manuvere.

Yes, there are commonly voltages present due to poor grounding and wiring. Most guys have to deal with the crap a club provides without being able to rewire stuff, measure voltages and all this stuff that can't be done before a show.

The cause for this is very simple: Guitar manufacturer's have been wiring guitars to be potentially lethal since the beginning. They connect the string ground to the audio ground. I'm still amazed that someone who was killed didn't have some litigious lawyer file against Fender and take a 2 million dollar cut out of their profits. That would have solved this problem.

The simple fix is to install a small .02 uf 600v capacitor in series with that wire that connects to the bridge. Replace metal volume/tone knobs with plastic ones.
When you play, do not touch the plug as it's still at DC ground potential if you are to sing.

At your next gig, thank me.

Jim Williams
Audio Upgrades
Old 22nd May 2007 | Show parent
  #25
Lives for gear
 
1 Review written
🎧 15 years
Jim,

I will have no problems thanking you at the next gig!!

.02 uf 600V cap on the ground wire to bridge.....

I am curious can I use any kind of cap, and what is the corner frequency? will this basically just block all DC and let AC through and then I am done?

should I expect a change in tone?
Old 22nd May 2007 | Show parent
  #26
Gear Guru
About any cap will do, you don't need a polyprop audio cap for this. A ceramic is fine. It works like a classic high pass filter. The 60 hz at low impedance is blocked by the cap so only the higher harmonics pass. These are not dangerous and the hand will still "filter" the buzz away like before. The difference is you are dealing with millivolts of the 60 hz's harmonics instead of volts.

Proper shielding of the cavity, the pickups and wiring will prevent the buzz when hands are removed. My Telecasters with stock pickups are dead quiet if I remove my hands as the pickups are shielded. I have no hum or harmonics as they are electronically hum canceling. They have an 80 db s/n ratio, better than many pieces of recording gear.

Jim Williams
Audio Upgrades
Old 22nd May 2007 | Show parent
  #27
Gear Guru
 
tINY's Avatar
 
1 Review written
🎧 15 years


The other thing a lot of guys do is use a wireless guitar transmitter for gigs at small clubs......



-tINY

Old 22nd May 2007 | Show parent
  #28
Lives for gear
 
1 Review written
🎧 15 years
Jim,

are you saying that the electical shock is occuring at 60 hz?


I was in a local guitar shop today and someone told me that someone they know blew up a small PA in that club...apparently the building isn't grounded.
Old 22nd May 2007 | Show parent
  #29
Lives for gear
 
A27Hull's Avatar
 
🎧 15 years
Quote:
"They also allow a small amount of 60HZ AC leakage to the equipment's case ground. There are special safety-rated caps for this called Y-capacitors that you must use to meet IEC and UL regulations."
This explains where the voltage is coming from. Thank you very much John and Jim!
Old 22nd May 2007 | Show parent
  #30
Lives for gear
 
JohnRoberts's Avatar
 
🎧 10 years
I won't guess which common problem is the source of your shocks, but no guitar mfr. is likely to lose a lawsuit for connecting anything to a safety ground. OTOH I wouldn't mind making some of those old 2-wire line cord guitar amp designers, who occasionally grounded chassis to hot through a cap, to play their own amps in the rain. tutt

Common cause of dangerous shocks, other than faulty gear is bad facility wiring, (thus my earlier advice to use an extension cord to plug into same mains circuit). If you have a voltmeter measure the voltage and current between guitar/mic.

I am aware of musicians being killed by properly grounded guitar amps in a house with miswired outlets. UL (the safety agency) testified in court and blessed the amps. The house was condemned, until wiring corrected.

I am not aware of specific deaths, but many serious shocks from mics, axes, and sweaty musos.

Danger Will Robinson.

JR
πŸ“ Reply
Post Reply

Welcome to the Gearspace Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…

Forum Jump
Forum Jump