Stage Electrical Safety — Part 1: Volts

Aug 21st, 2010 | By | Category: Musician Safety
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The No~Shock~Zone:  Stopping Hums, Buzzes and Shocks on Stage — Part 1: Volts
©Mike Sokol 2010 – All Rights Reserved

If you’ve read the survey we’re running at www.prosoundweb.com, you’ll discover that 71% of the musicians and sound technicians surveyed have been shocked by their mics, instruments and sound systems.  What follows is the first in a 12-part series about basic electricity for performers and technicians and how to safely stop hums, buzzes and shocks from your amps and equipment. 

Review the 71% report at http://www.noshockzone.org/musician-shock-survey-in-progress/.

This series of articles is provided as a helpful educational assist with sound system setup and musical performance, and is not intended to have you circumvent an electrician or qualified audio technician. The author and the HOW-TO Sound Workshops will not be held liable or responsible for any injury resulting from reader error or misuse of the information contained in these articles. If you feel you have a dangerous electrical condition in your PA system or instruments, make sure to contact a qualified, licensed electrician or audio installer.

Amp Safety

Guitar amps and mixing boards as wired from the factory are inherently safe, but they can become silent-but-deadly killers if plugged into an extension cord or wall outlet that’s improperly grounded. This is because guitars are held in your moist hands while your wet lips are touching another electrical circuit, the microphone. It’s up to you, the musician or sound tech, to make sure your guitar or microphone is never electrified due to poor maintenance, bad connections or a broken-off ground plug. This so called Hot-Chassis problem is what causes a tingle or shock when you touch the mic with one hand or your lips while holding a guitar with your other hand.

Just the Basics

Most musicians really don’t want to learn about electrical engineering, or even how basic electricity works. Everyone, however, should learn how to test for and avoid electric shocks on stage. With that in mind, there are some novel ways to think about and teach basic electricity to the musician and technician. This article series promises little or no math, no fancy schematic reading and certainly no memorization of formulas. It’s our privilege to teach you basic electrical safety as long as you do one thing for us — let us know if the information is making sense and is helpful to you. So after reading this post, give us some feedback — good or bad. The failure of the student to learn is the failure of the teacher to teach, and we take our teaching job seriously. So feedback is encouraged.

Why Do We Get Shocked? (What is This Volts Thing?)

What’s so hard to understand about electrical shocks in general is that they don’t seem to happen for any obvious reason. For instance, you can watch a pigeon on a power line that’s not being shocked, yet sometimes just holding a guitar while standing on wet ground can bring you to your knees. Just why is that?
 
Well, the first thing to understand about electricity is the concept of Voltage. Think of Voltage as electrical pressure, just like the pressure in a tank of water. Now in a tank of water we measure pressure in something called PSI (pounds per square inch), which will, of course, increase if we get a deeper tank. This pressure is caused by the pull of gravity from the Earth and if you hook up a hose to the tank, the water will flow toward the ground. So while 10 PSI of water pressure from a short tank might give you a trickle of water when hooked up to a hose, 100 PSI of water pressure from a really tall tank gives you a stream that will spray much farther.
 
Water — and electricity — tries to flow to the side of least pressure. You can imagine that if a pipe is connected between two tanks with exactly the same water level and pressure (say, 100 PSI) there will be no flow of water through the hose. It just sits there and does nothing because the system is equalized. However, if you connect one tank with 100 PSI of water pressure to another tank with 10 PSI of water pressure, water will flow from the high tank to the low tank. We measure this water flow in gallons per minute.

Under Pressure

The same thing happens with electricity. You’ve often heard of “completing an electrical circuit,” but think of it as pipes between different electrical pressures. Getting back to the pigeon on the power line, if both of the bird’s feet are on the same wire, they’re at exactly the same electrical pressure. Because they’re at the same pressure, there’s no electrical current flowing through the bird. If, however, the pigeon is unlucky enough to touch one foot on a power line and a wing to the grounded metal power pole, then his foot will be at 1,000 volts (think PSI of water pressure) and his wing at 0 volts (think an empty tank with zero pressure). This will cause a lot of current to flow through the bird, which we’ll measure in Amperes. And indeed 1,000 Volts across a pigeon can cause a bird explosion.
 
Hot Chassis Shocks

Now, consider your guitar. Sometimes you may feel a shock when you touch one hand on the guitar with the other hand on the mic. What’s happening is that there could be an electrical voltage (think pressure) on the strings of your guitar, which is waiting for some different electrical voltage level to head towards. If your entire body is at the same voltage, then like the pigeon every part of you is at exactly the same voltage. And like the pigeon, there’s no current flow and you feel no shock. However, if your one hand is on the mic at essentially zero volts and your other hand is on your guitar at 120 volts due to a wiring problem, you become the pipe and the different electrical pressure (Volts) will push current (Amps) through your hand, arm and chest cavity, then out through your other hand. If your hands are dry, there might be so little current flow that you might not even feel it. But put a damp hand on your guitar strings and wet lips on the mic and you’ve made a good connection from the power plug of your guitar amp to the ground of the PA system. In the case with an ungrounded guitar amp, a lot of current will flow through your body, which you’ll quickly recognize as a shock  and potentially an electrocution.

Heart to Heart

The dangerous part of shocks is when this electrical current flow goes through your chest cavity since right in the middle of you is your heart, and hearts don’t like to be shocked. That’s because your heartbeat is controlled by electricity which comes from your own internal pacemaker. And just like a clock radio can be scrambled by a nearby lightning strike, even a small amount of electrcity passing through your heart can cause it to start skipping beats and cause a heart attack. Just how little? Glad you asked.

I’m sure by now you’ve seen the 20-Amp marking on a circuit breaker. That means it can supply 20 Amps (Amperes) of current flow when asked to do so.  Again, you can think of it as gallons per minute of flow, and Amps are indeed a count of electrons per second flowing through a wire (think pipe). Much more on that later, but it takes less than 5 milliamps of current to cause your heart to go into fibrillation mode. That’s just 5/1000 of an Amp or 0.005 Amps of alternating current to cause what’s essentially a heart attack. It takes just 30 Volts of Alternating Current (AC) to stop your heart if your hands are wet. On the strange-but-true side of the coin, while 60 Hz Alternating Current (AC is what comes out of your wall outlet) can cause your heart to go into fibrillation and stop pumping blood, the emergency rescue crew will use Direct Current (DC) of several hundred Volts to reboot your heart and get it beating regularly again. That’s what they’re dumping through the paddles placed on your chest — Direct Current from big capacitors like you see charging on the TV dramas before they yell “Clear!”

Play It Safe

The first rule of staying safe from electrocution is to keep your heart out of the current flow. You can see that getting shocked from hand to hand or hand to lips or feet is about as bad as it can get. That means if you’re plugging in your guitar amp with one hand, the last thing you want to do is hold onto the metal rail around the stage with your opposite hand or be kneeling on the wet ground. If you have two points of contact and something goes wrong (like you touch a bare wire), the current will flow to your opposite hand or feet, passing through your heart in the process. So always use just one hand when plugging or unplugging your power cords for your amps. Not doing so is to invite death by electrocution, and, really, who wants that?

Keep Grounded

Take a look at a typical 120-volt grounded wall outlet on the left. The top half of the illustration shows the sideways slot of a 20-amp outlet, while the bottom half shows a more common 15-amp outlet. In both versions you’ll see a HOT connection (the short blade), a NEUTRAL connection (the tall blade), and a U-shaped GROUND connection (called the safety ground). Those ground blades are on the power outlets and plugs  for good reason. If something goes wrong internally with your amp (say a wire shorts to the chassis or a power transformer gets leaky), that ground blade is supposed to divert the voltage from the strings of your guitar through the ground in your power panel which will then trip the circuit breaker. If the circuit breaker doesn’t trip because you’ve eliminated the safety ground by breaking off the ground blade of your power cord, then you may have an electrically hot guitar or microphone in your hands. And you may not realize it’s electrically hot until you touch something else that’s grounded with your other hand or lips, just like the bird holding onto the power line with his feet doesn’t get shocked until his wing touches the grounded metal power pole. Then it’s lights out!

So if you circumvent that safety ground by cutting off the ground blade or using an adapter plug like you see on the left  in an attempt to stop hums or buzzes in your sound system , you can put your heart in the middle of the ground path and risk your life every time you plug in your amp. Don’t do it.  Always ground your amp and PA system properly.

Make your stage a No~Shock~Zone

By grounding every amp and mixer in your sound system properly you will help create a “No Shock Zone” on stage, making it a safe place to perform without fear of getting shocked or electrocuted. So take this seriously… if you or anyone in your band is getting shocked by a guitar or mic on stage or even in your practice basement, now is the time for action. We’ll be running a 12-part series on how to stop Hums, Buzzes, and Shocks on stage right here at www.NoShockZone.org, so read along and learn how to keep safe from shocks on stage while getting rid of those pesky hums and buzzes in your sound sytem.  

Quick Tips
  
  • Use only one hand to plug or unplug any power cables for your amps.
  • Don’t cut off the ground blade of your amp or mixer power plug to stop a hum in your PA.
  • Never stand or kneel on wet ground while touching a guitar, keyboard or microphone.
  • If you feel a shock on stage, avoid further contact until you can determine the source of the problem.

Part II of this series will cover current (amperage) and the basic concepts of why ground loops happen in sound systems. Plus we’ll show you why the ground lift switch on a DI box is so handy. Stay tuned and stay safe.
 
Mike Sokol is the chief instructor for the HOW-TO Sound Workshops (www.howtosound.com) and the HOW-TO Church Sound Workshops. He is also a musician and an electrical and professional sound expert with 40 years in the industry. Visit www.NoShockZone.org for more electrical safety tips for musicians. Contact him at mike@noshockzone.org or mike@fitsandstarts.com.

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17 Comments to “Stage Electrical Safety — Part 1: Volts”

  1. Nick says:

    Thanks for this. I have been looking a long time for an article like this that I could understand.

    I have gotten zapped a couple of times at a particular venue. I went and talked to the guy at the music shop and he said the wiring was bad in the place and that I should buy a power conditioner. Since then I’ve looked online and everything I’m reading seems to say that power conditioners don’t prevent you from getting shocked at all so I’m thinking the guy was just trying to sell me something.

    Do you have any insight into this? Do power conditioners prevent you from getting zapped if the building has old or bad wiring?

    Thanks again!

    • Mike Sokol says:

      Nick,

      The unfortunate truth is that power conditioners do nothing to protect you from shocks due to bad grounds. They only serve to give you a false sense of security. Now from personal experience I know that a “surge protector” can save your freezer in the basement when a nearby lightning strike hits the ground and causes a voltage spike in the power line. In my case it was pretty obvious since the power strip’s circuit breaker had tripped and wouldn’t reset. An autopsy revealed that the little MOV (Metal Oxide Varistor) was shorted out with a big black spot where the voltage punched through it. But that’s about all they’re good for.

      The only real way to protect yourself is to make sure that all of your stage gear has the proper ground blades on the power cables, and that the power outlet you’re plugging into has a proper “safety ground”. Note that there’s a real easy way to confirm if your amplifiers or microphones are “electrified”. If you read the article we just published about RV Hot Skin problems at http://www.noshockzone.org/rv-electrical-safety-part-iv-%e2%80%93-hot-skin/ you’ll see that a Fluke VoltAlert tester will beep if there’s as little as 40 volts on the body of a vehicle. Well, it works exactly the same for guitars and microphones. So this $30 tester allows you to check mics and amplifiers on stage for shock hazards without actually putting your hand on the mic or guitar. Stay tuned to the No~Shock~Zone Musician-Safety area for articles on how to confirm sound system ground safety, but these RV articles have much of the safe information and are online right now.

      Good luck and stay safe…. Mike Sokol

  2. Jonathan Johnson says:

    Would you recommend using GFIs on any circuit that audio equipment is plugged into?

    • Mike Sokol says:

      The problem is that a lot of older audio gear (tube amps especially) have quite a bit of leakage to ground due to internal insulation that’s degraded. And while the safety ground connection of the gear’s power plug should protect you from shock, that same current leaking to ground could cause “false tripping” of the GFCI breaker. That will probably make musicians use a ground-lift adapter on the power plug which now leaves the chassis of the gear electrified. So it’s a real catch 22 that’s not easily resolved. Add in the fact that the 2011 National Electric Code is calling for GFCI outlets on all stages, and it’s going to get a bit crazy. I don’t have a quick answer, but I am developing a simple way to test gear for abnormal ground leakage currents and ways to deal with it. I should have some concrete answers in a few months.

      JMS

      • Jonathan Johnson says:

        I see your point about “false tripping.” If a stage is equipped with GFCI breakers, and a musician does use a 3×2-prong adapter to avoid the tripping, shouldn’t the GFCI still trip if current leaks through the musician to ground? Of course, it will annoy the musician that his amp keeps tripping the breaker. I’d rather he be annoyed than dead.

        • Mike Sokol says:

          Yes, the GFCI doesn’t need the ground wire at all to detect an imbalanced current and trip. So in theory you are correct. But I would think they’ll get a more than little “annoyed” the second time the breaker trips. There’s no way to bypass a GFCI breaker (that I know of) so I’m sure they’ll just run a long extension cord from an unprotected outlet. to power their amp. At least that’s what I would do in a pinch to keep a band running. If that extension cord is grounded, then the musician is still safe. But if it has a defeated ground, then it’s big shock time.

          That’s the problem with stage shocks, it takes a combination of bad circumstances and bad luck to put you in a bad situation, and then you’re seriously shocked or electrocuted. More to think about…

          Mike

  3. jean says:

    Thank you very much for these great articles, and I look forward to the upcoming segments. Having seen a few colleagues get shocked lately, I’m trying to learn more and do what I can to prevent this sort of thing in the future. I’m now checking ground each time I go to a new venue, plugging into GFCI converters, and reminding others that, if there’s no ground when you plug in, the musician becomes the ground wire. That said, it would be good to know if a GFCI converter is a good fall-back for two scenarios:
    1. when someone brings an amp to a gig that has had the ground prong removed from the 3-prong plug, or
    2. when someone brings an older guitar amp with a two-prong plug and a ground switch (I don’t fully understand what the ground switch on an older amp does, but I gather that it doesn’t actually achieve grounding, it just just helps avoid hum).

    I appreciate that leakage from older amps that might cause “false trips”, but how would one know the difference between a false trip and a real safety hazard based only on the number of GFCI trips? If the GFCI tripped a few times, I think I might take that as a sign to go get my back-up amp with the modern, fully intact 3-prong plug out of the car. (It might not have the same sweet tone as the vintage amp, but at least I’d know it’s safe). What do you think?

    Thanks again for the great, user-friendly information you are publishing.

    -jean

  4. Mike says:

    The way I like to explain it to people is that electricity wants to get to the ground, and will always take the path of least resistance to get there. If there is no low resistance path to ground (safety ground through building wiring), and a leak occurs in a piece of equipment, the next person to touch the equipment could easily become part of a new path the electricity takes to reach the ground.
    Something else worth noting is that if a surge protector is ungrounded, it will not protect against surges. It must have a ground conductor to divert the surge to the ground.

  5. KC says:

    Note that the Fluke voltage tester were recalled due to false negative.. Check it out before purchasing new/used and if you already own one.

  6. Jim Conklin says:

    Some older amps featured a polarity switch which would sometimes eliminate the problem.

    Is this a safe circumvention? Are there any external protections that a musician can run the power through to eliminate the shock potential.

    In my experience, it’s usually the house current in old buildings at the source of the problem and even with grounded plugs on both the PA system and the amplifier you can experience a scary and annoying shock.

    If not, what then, is the answer aside from telling the bar owner to upgrade his system, unplugging and foregoing the gig?

    Thanks for any practical advise you can provide.

    Jim Conklin

    • Mike Sokol says:

      I faced the same issues back in the 70’s, but since I was an EE with a Master Electricians License there were things I could do with the wiring in the clubs I played in. I rewired many of the stages with grounded outlets, and finally built my own power distro box when things got really crazy for lighting power.
      However, for most musicians you can either take the gig as is, or walk out and lose that income.
      You can, in fact, add contractor extension cords with built-in GFCI (Ground Fault Circuit Interrupt) breakers. These will trip automatically if you sustain a big shock, thus saving your life. But since they’ll power off your amps and the sound will stop, many musicians won’t have anything to do with them. However, getting your entire back-line (stage amps) powered from a single outlet, and then running a long extension cord from that same outlet strip back to the mixing console position will eliminate any shock potential between your stage amps and the microphones. You can then plug all your PA amplifiers into a separate outlet, hopefully on it’s own circuit breaker. But watch out for RPBG (Reverse Polarity Bootleg Ground) outlets, which can blow up your mixer and power amps/speakers. For an extended discussion I started on a electrical inspectors forum, see http://forums.mikeholt.com/showthread.php?t=146019 and http://www.rvdoctor.com/2001/07/friends-of-gary-mike.html as well as a video at http://www.youtube.com/watch?v=iLk-6pvSlWg

  7. denma says:

    thanks very informative!

  8. Chris says:

    Thank you,

    My teacher brought us to this site to read up on ground plugs and safety. This was very helpful and I liked the diagrams, great stuff.

    • Mike Sokol says:

      Excellent. I’m curious as to what class you’re taking. And please have your teacher contact me if he or she has additional questions about electrical safety or electricity in general.

  9. Boris says:

    Thank you very much for the website. I have been getting shocked for a few weeks and the sound man keeps saying “There is no problem with the electricity. It must be your equipment”. It was hard for me to explain that my guitar is not carrying any power signal just like any other guitar (or hard for him to understand, I guess…) but, thanks to you, now I have nice examples to tell everything briefly.
    But I really want to see the rest of the 12 parts. It looks like you wrote something after 3 years but nothing about the musician safety. If the only problem is financial support, have you thought embedding a PayPal donation button to your website? Most of the musicians (especially those in not US like me) probably can’t help about sponsorship but donate and show how thankful they are as long as they found the website helpful.

    Cheers,
    Boris

    • Mike Sokol says:

      I’m finishing an ebook on Pro-Sound and musician electrical safety next month. It will be available on Kindle for $9.99 which should be affordable by everyone.

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