Microphone Shock!

Naggon

Naggon

Nov 8, 2006
215
23
4,551
Vancouver, BC
#1
Hi all,
I've seen a few other threads about this, but never with a good conclusive solution, so I figured I'd try here.

I play bass and sing, and I'm been getting zapped by the microphone all the time lately! I recently went on tour, and it was a problem and about half of the venues we played. I recently moved into a new rehearsal room, and it's a constant issue. Whenever my hands are touching my strings and my mouth touches the mic, I get a jolt.

-I've tried plugging my amp into the same outlet as the PA, didn't solve the problem.

-I've tried plugging into a different outlet, didn't help either.

-I've tried different basses, no difference.

I've resorted to just tying a handkerchief around the mic, but this only works for a song or two until it gets wet. Using a pop filter/not touching the mic isn't an option as I play loud music in small-ish clubs, which usually have poor PA systems, and I'm constantly fighting to be heard/to hear myself.

Help, please!!
 
#2
First thing is to stop crazy things like wrapping the mic. There's a real possibility you will die. It's not rumour and fallacy - you have a real fault and it needs sorting out.

First thing is to find somebody you trust who is competent to test it. Stick a meter between the mic body and the guitar strings and measure the voltage. It's probable that it is around half your supply voltage. This usually indicates a tube amp with a fault and the centre tap of the transformer putting this voltage onto the ground. It's far less common to find a similar fault in the sound system. Tube amps generate high voltages to make the tubes function and a breakdown in the transformer windings can easily produce this problem. In some cases, the current - which is the killer, not the voltage can be substantial - and it takes milliamps, as in thousandths of an amp, to stop your heart. The old saying in the UK is Volts Jolts, but Mills Kills.

If you're the path between the mic and your guitar, that goes directly across your heart. Get a bit sweaty and the current can go up!

The test process should be to check your guitar amp first - volts between the ground of the jack and the real ground. Anything more than a few volts and there is a fault! If there is no voltage between these points, then move to your PA and repeat - is the ground and the mic body at the same potential? It should be.

If you cannot do these tests safely, find somebody who can.

This is not a minor issue - it's a life changing process waiting to happen.

DO NOT try to do anything yourself if you are not competent - tingles like this usually make you wince and get cross, but this is because the current passing is small. 30mA could kill by stopping your heart, or starting it fibrillating.


Please don't use it - while most times it won't be anything more than a minor low current leakage, it IS a fault and faults often suddenly get worse.
 
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#4
Is your amp properly grounded?
ditto on the PA

Do you have a plug tester for making sure the outlet you're plugging into is grounded?

reciptical-outlet-tester.jpg
 
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#6
@paulears Thank you for the warning. I had no idea the issue was so serious. It's happened to me dozens of times by now, but never more than a slightly painful jolt that makes it practically impossible to comfortably sing. I certainly take it more seriously now.

@Killed_by_Death I've read that you can get these outlet testers quite cheaply, so I'll get one today. My primary amp is a brand new Orange Bass Terror 1000, which doesn't have a built in ground lift. I also use a Mesa Boogie Bass 400+ which does have a ground lift, however, I'm still having the same problem with both amps, (and with the ground switch in both positions) at many different venues.

@Oddly No, I don't typically bring my own mics to a gig, so this is with many different mics and cables at different venues.

Does anybody know if there's a way to check if an amp is properly grounded/to properly ground an amp? I'm still quite confused on the issue and not sure how to solve it.

Thanks so much, kind people!
 
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#7
A ground lift on an amp doesn't do what it appears you think it does.

Measure continuity (Resistance of 0 Ohms) from the grounded side of your instrument cable (when plugged into the amp) to the ground prong of the amp's power plug (also when plugged into the amp & not the wall socket).
 
#9
@Killed_by_Death I've read that you can get these outlet testers quite cheaply, so I'll get one today. My primary amp is a brand new Orange Bass Terror 1000, which doesn't have a built in ground lift. I also use a Mesa Boogie Bass 400+ which does have a ground lift, however, I'm still having the same problem with both amps, (and with the ground switch in both positions) at many different venues.[/QUOTE]at the risk of repeating something mentioned above, let me add a caveat !!

NEVER, EVER, EVER, GROUND LIFT a TUBE AMP.... DOING SO can KILL YOU !!

One should never, ever ground lift any amp to be honest, as it's masking the symptoms of a larger problem.
If you are getting shocked at multiple venues with multiple different mics, amps and basses.. I'm a bit stumped.
Usually the event indicates bad grounding somewhere in the power loop.. either the outlets, a ground-lifted bass amp, or somewhere in the venue.
My first thought was are your basses grounded and shielded?
Do they make noise when plugged into your amps?
We these your amps or house amps and mics?
 
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#10
@s0c9 Woah, ground-lifting a tube amp can kill you - another thing I certainly did not know. Not sure why so many amps have built-in ground lift considering its so dangerous, but I'll take your word for it. No need to risk that.

I certainly assume my basses are grounded and shielded... I have a p, a ricky, and a lado, never messed around with the electronics, and I've had the same problem regardless of which one I use. They generally don't make much noise when plugged into my amps besides the usual bit of occasional feedback when playing with gain at high volumes. Never much compared to guitars, etc.

I always use my own amps (Orange Terror and Mesa Boogie 400+) but house mics and PA systems, and the problem is consistent regardless of which of my basses/amps I'm using, at many different venues. I don't ALWAYS get shocked - just perhaps around half the time. It's utterly baffling to me.

And @RoadRanger Yes, I'll certainly take my amps into a tech and see what I can learn. I agree, haha, this is much cheaper than a funeral, and I'm very happy to treat my gear right and take good care of it - I've just been baffled and unsure of even which pieces of equipment I needed to get looked at.

It sounds like the general consensus is that the issue most likely is coming from my amps. Although it's a bit odd and unusual that I'd be having the same issue from both amps, perhaps reality is just bizarre and they've both suffered a similar malfunction at the same time. Stranger things have happened.

I'll take them in to the tech and see what I learn.

Thanks for the help, amigos. Perhaps you've saved my life! TalkBass is good for something after all, it seems.
 
#11
Naggon said:
Not sure why so many amps have built-in ground lift considering its so dangerous,
Click to expand...

Ground Lift isn't what you think it is. The ground lift on amps today is for removing the amp's internal ground wire from the DI output.

The Mesa Boogie Bass 400+ that was mentioned does have a selector for ungrounding the power input, which seems pretty reckless.
 
#12
Killed_by_Death said:
The Mesa Boogie Bass 400+ that was mentioned does have a selector for ungrounding the power input, which seems pretty reckless.
Click to expand...
I believe that just switches off the "death cap" for when you are using a proper three prong outlet - the early three prong cord amps had that so they could still be used with two prong outlets for those who didn't value their lives LOL.
 
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#13
Naggon said:
@s0c9 Woah, ground-lifting a tube amp can kill you - another thing I certainly did not know. Not sure why so many amps have built-in ground lift considering its so dangerous, but I'll take your word for it. No need to risk that..
Click to expand...
as @Killed_by_Death stated above "Ground Lift isn't what you think it is. The ground lift on amps today is for removing the amp's internal ground wire from the DI output."
the "ground lift" I"m talking about is NOT that switch on the back of the amp.. It's using an adaptor that removes the "ground" pin from the wall plug, often used to remove "hum" or "noise" induced into the amp due to bad house grounding ..
AGAIN.. NEVER "GROUND LIFT" the POWER SUPPLY on a TUBE AMP!

This is standard 3-pin US 15-amp plug

upload_2017-8-22_8-25-14.png


This is a ground lift adaptor - NOTE the missing GROUND PIN !! You put the 3-pin into the back, and it "LIFTS" the ground...
I CANNOT OVER-EMPHASIZE it enough !!

DO NOT USE THIS WITH ANY TUBE AMP!

upload_2017-8-22_8-24-23.png
 
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#16
s0c9 said:
as @Killed_by_Death stated above "Ground Lift isn't what you think it is. The ground lift on amps today is for removing the amp's internal ground wire from the DI output."
the "ground lift" I"m talking about is NOT that switch on the back of the amp.. It's using an adaptor that removes the "ground" pin from the wall plug, often used to remove "hum" or "noise" induced into the amp due to bad house grounding ..
AGAIN.. NEVER "GROUND LIFT" the POWER SUPPLY on a TUBE AMP!

This is standard 3-pin US 15-amp plug

View attachment 1911984

This is a ground lift adaptor - NOTE the missing GROUND PIN !! You put the 3-pin into the back, and it "LIFTS" the ground...
I CANNOT OVER-EMPHASIZE it enough !!

DO NOT USE THIS WITH ANY TUBE AMP!

View attachment 1911983
Click to expand...
That's not a "ground lift". It's a three prong to two prong adapter. The tab on the male side is supposed to be connected to the screw of the wall outlet's cover plate making a mechanical ground through the wall box. Yes. Most people use them for the purpose you describe but that's not the intended purpose.
 
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#17
Yes, it's supposed to provide an alternate way to ground it, which is why the the ring/loop sticks out the top.
You can ground it to another device that's already grounded, or link it up to another device you're pairing with to stop a ground loop.

I think I wouldn't last very long as a performing musician, because I wouldn't even play if I had to play on an amp that wasn't grounded properly.
 
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#18
Gluvhand said:
That's not a "ground lift". It's a three prong to two prong adapter. The tab on the male side is supposed to be connected to the screw of the wall outlet's cover plate making a mechanical ground through the wall box. Yes. Most people use them for the purpose you describe but that's not the intended purpose.
Click to expand...
Come on, be honest! Have you EVER seen one of those used as intended screwed into the wall.. ?? In 25 yrs of doing sound... I never have.
Yes, they are supposed to be used like this, but I've never seen one at at a gig.
3_groundADAPTER_w.jpg


They are used as ground lifts IME. I have a couple in my gig bag :)
blog-post-the-principle-of-ground-lift.jpg
 
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#20
s0c9 said:
Come on, be honest! Have you EVER seen one of those used as intended screwed into the wall.. ?? In 25 yrs of doing sound... I never have.
Yes, they are supposed to be used like this, but I've never seen one at at a gig.
View attachment 1940853

They are used as ground lifts IME. I have a couple in my gig bag :)
View attachment 1940850
Click to expand...
What you have and how you use it is up to you. You can call it a pogo stick if you like. That's not what it is, and yes, I have seen them used as intended. I'd be a lousy electrician if I used them any other way. My guitarists, that own and set up our PA, tried using those and I refused to play if they did.
 
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