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Stopping Hums, Buzzes And Shocks On Stage — Part 1: Volts
The first in a multi-part series on based upon our ProSoundWeb electrical safety survey.
Aug. 27, 2010, by Mike Sokol
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  Audio Basics, Audio, Church Sound, Worship Sound, Safety, Stopping Hums Buzzes And Shocks On Stage, Electricity

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).

Click to enlarge.

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.

I’ll be running this 12-part series on how to stop Hums, Buzzes, and Shocks on stage right here on ProSoundWeb, 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 system. For more information, fee free to check out the No Shock Zone Website. 

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 I’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 and the HOW-TO Church Sound Workshops. He is also an electrical and audio expert with 40 years in the industry. Visit the No Shock Zone Website for more electrical safety tips.


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Comments (2) Most recent displayed first
Posted by Jonathan Johnson  on  08/30/10  at  03:25 PM
Do you recommend installing GFI (Ground Fault Interrupter) breakers on stage & PA circuits?
Posted by John E. Lawton  on  08/27/10  at  04:16 PM
A hot chassis is--contrary to the way you've loosely defined it above--a chassis (or metal framework for mounting electrical- or electronic-components) where the metal chassis is purposely connected to a power-supply positive- or negative-voltage, rather than being connected to (0 volts) ground (or "earth" if you speak "British English" rather than the Americanized version). Hot chassis are regularly, commonly--and primarily, inexpensively!--used to make TVs and other equipment and are reasonably safe when properly maintained and operated.

What you're most likely talking about--as a former electronics technician--is a situation whereby a chassis has become "hot" through a wiring-fault.

While most factory equipment should be safe (one shouldn't trust it, but, should test it!), a lot of amplifiers and other sound-equipment get modified, often by people who are not trained to do so. Thus, they have wiring faults.

Modern 110-120 VAC equipment that uses a two-blade, polarized plug, is reasonably safe--without a ground-wire--provided it is used properly. The same should be true--but isn't always--for three-wire, grounded AC equipment. The ground-wire is there primarily to short circuit abnormal voltages to ground, i.e., if a hot-wire to a motor breaks, the ground-wire provides a short-circuit, low-resistance path to ground for the circuit, lessening the chance of accident by shock.

It is relatively simple, using a VOM with one lead with a clip, to check to see if an abnormal voltage exists between two pieces of equipment. Placing the meter on its highest AC range, attach the lead with the clip, using one hand with the other one in your back pocket, to the chassis of one piece of equipment, to a shiny screw, grounding post, etc. Then, while still keeping your other hand in your back pocket (while not standing on a wet-carpet on wet-cement, in a damp basement; staying out of puddles, bathtubs, etc.) touch the other lead to a shiny screw, metal edge, etc. on the other piece of equipment. If you read even the slightest voltage, remove the last lead, reset the meter to a lower range (with one hand in your back pocket unless you disconnect the other lead first!), and repeat to get a better idea of exactly how many volts difference exist between the two chassis (between amp chassis and mike, etc.). Any indication of more than a very small voltage (0.01v to 0.1v) should be checked out further, preferably by someone certified by the manufacturer to do repairs on those pieces of equipment.

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