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Thursday, March 20, 2008

You Complete Me (and the Circuit)

posted by on March 20 at 15:30 PM

shock1.jpgThe Croc’s Jim Anderson talks about electricity and grounding and how to safely check a mic to see if there is current running through it.

Ever get the shit shocked out of you when you touch the mic?

Something’s not grounded. When you touch a microphone plugged into a PA that’s not properly grounded, you complete the circuit. Voltage passes through you. It’s unpleasant and can wipe your mind. It can make you wish you were in diapers. It can also be lethal.

Electrical current can come through the wall, through the plug, into your amp, through the metal quarter inch cable, and into your guitar or bass with its metal strings. Then it goes through you, until you touch something else metal, like the microphone. The human body is made up of lots of water and salt and therefore is highly conductive.

The term “ground” refers to a connection to the earth, which serves as a reservoir of charge. A ground wire provides a conducting path to the earth which is independent of the normal current-carrying path. This protects against electric shock. Electricity is always trying to find that ground. Sometimes you become the path of least resistance.

Older guitar amps with two-prong plugs like the Airline are notorious. That missing third prong is the ground. The Airline also doesn’t have a polarity switch. There you are at the club, excited to use your vintage Airline which is pulling 120 volts. The chorus pedal you’re playing is pulling 110 volts and everything is plugged into the same ungrounded circuit. Can you say unstable? It’s mic check time:

Testing, testing, Z-BAM! A shock is delivered to those gentle lips. Shock the monkey. Flash of white. Surge of current. You jump back, can’t remember any of your songs, and sing the Kermy version of “Somewhere Over the Rainbow” over and over for the rest of the night.

Jim Anderson says:
The ground is there to dispose of, relieve, and neutralize any excess current in case there’s a fault. You want the current to ground so it will blow a breaker or a fuse, before it blows through you. In Europe the 220 volts will knock you on your ass. Here, the lower voltage is sometimes even worse, because people can become stuck there and defibrillate. I’ve seen people put their wet full cocktail on top of an outlet. That’s a frustrating thing to see.

Is there any safe way to check the mic to see if there’s any current running through it?
Jim: Yes. Set the guitar down, hold guitar chord between your thumb and forefinger, wrap the cable through your other fingers, and touch the back of that hand to the mic. The skin on the back of the hand is more sensitive. Also if there is current running through that mic, the natural muscle contractions of the hand and arm will pull you away if there’s a big shock.

RSS icon Comments

1

My friend's Fender Bassman is notorious for this. It has a 2-pronged plug and and no polarity switch. Getting shocked is usually mild and annoying, but this thing can knock you on your ass.

How hard would it be to replace the power chord in something like this? Can it be wired for a 3-pronged plug?

Posted by Jeff | March 20, 2008 4:06 PM
2

I have the same problem with my 1961 Fender Super that play through everyday. I leave it plugged in at our practice space, so the plug never gets reversed there. But when we play shows, it's always a crap shoot, and I usually get hit.

You can replace the entire cord, but there are two small issues: 1) Finding something metal inside the amp to land the ground on, and 2) Losing the vintage aspect, because of modification.

But I'm starting to think that it might be worth it.

Posted by Daniel G. Harmann | March 20, 2008 4:21 PM
3

Oh I love getting shocked. Its best if the club is real dark and you can see the arc from the mic to your lips. Yummy!!!

Posted by drheavy | March 20, 2008 4:32 PM
4

Don't modify - electrify.

Posted by Frankenstein | March 20, 2008 4:43 PM
5

I saw a couple of people get the crapped shocked out of their lips at sxsw. Not pretty.

Posted by rk | March 20, 2008 4:55 PM
6

Radio towers...

For all the times I've been shocked by improperly grounded equipment, it was climbing one of the the WMAL radio towers in Potomanc, MD that I learned a lucky lesson in grounding.

Radio towers carry a pretty heavey charge, and are coated in a thick, latex paint. One night, some friends and I were climbing the WMAL tower in MD after a show. I was about 75 feet up the ladder, my friends just ahead of me, when I felt what I thought was a bad bee sting. Drunk as I was, I remember clenching the ladder and drawing my hand away. Finally manuevering to look at my hand, there was a white circular burn mark where I'd touched an exposed peice of metal where the paint had chipped off the back of the ladder. When I looked up, I reallized my friends were far ahead of me. I'm pretty sure I lost 15 - 30 seconds of memory just kinda stunned, hanging onto this ladder like an idiot, staring into space like a deer.

I love telling this story, and I appreciated Jim sharing his tecnique for checking with the cord/back of the hand. Very cool.

Thanks Trently

Posted by Blue Nordie | March 21, 2008 2:06 AM
7

This article may save somebody's life one day... especially my own ::)

Posted by WOLF BLITZER: SPECIAL REPORT | March 21, 2008 3:48 AM
8

Fuck the vintage value--you have to be alive to collect that money. Adding a three-prong is so minor that the pricing impact is inconsequential compared to all the other things that have probably been done to a 40 year old amp over the years--new speakers, recones, various internal components, wear and tear, etc. And it affects the sound not at all.

Posted by Tiktok | March 21, 2008 7:30 AM
9

wet full cocktail? um...never mind. I hate that feeling of shock. It's been ages since it last happened but I really hate it. Jim Anderson is damn smart. I'm having a hard time visualizing how to test the ground with my hands.

Blue Nordie's radio tower story freaks me out. I used to know this guy who used to plug stuff in and pretend he was getting electricuted. He'd plug something in and then shake his leg real fast. He was so convincing.

Posted by Cedric | March 21, 2008 7:06 PM
10

wet full cocktail? um...never mind. I hate that feeling of shock. It's been ages since it last happened but I really hate it. Jim Anderson is damn smart. I'm having a hard time visualizing how to test the ground with my hands.

Blue Nordie's radio tower story freaks me out. I used to know this guy who used to plug stuff in and pretend he was getting electricuted. He'd plug something in and then shake his leg real fast. He was so convincing.

Posted by Cedric | March 21, 2008 7:06 PM

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