Sign up for ProSoundWeb newsletters
Subscribe today!

Don’t Kill The Artist! Electrical Safety On Stage
Some basic precautions and tests to reduce if not eliminate the possibility of electrocuting our musical friends
+- Print Email Share Comments (3) RSS RSS

Testing, Testing
So let’s say you’ve managed to make your system hum-free while maintaining your solid console and backline grounds.

Now the overwhelming goal should be proving, beyond doubt, that the system is absolutely safe. Four steps of progressively increasing intensity should be taken to insure this:

1) Meter the mic to the instrument strings. Touch bare metal on the mic - some mics have painted grills, so the meter will read “0 volts,” but there are often small spots where the paint has chipped away that can zap a singer.

Wireless guitars will always measure safe, but if there’s a hardwired spare guitar, it must be checked with the meter.

Even if a singer doesn’t play an instrument, keep in mind that barefoot singers and/or wet stages can be a problem if the stage is metal or if there are screws in the stage that attach to its metal frame.

Therefore, meter any metal that the performer may come in contact with. You’re looking for less than 1 volt or so, and be sure to check for both AC and DC voltages.

2) Turn on the guitar rig, and with the guitar plugged in, touch the guitar strings to a bare metal part of the mic. The XLR connector often provides a good bare metal connection.

Keep a volt meter handy to thoroughly check for any unwanted electricity dangers, and that includes testing mics and instruments like electric guitar

If the guitar rig produces an audible buzz when the strings touch the mic then there is a potential hazard.

And if the strings melt and a blue spark erupts, it’s a sure sign of things being not so good. If this happens, do not proceed to step 3 without resolving the problem.

3) Now comes the “fun” stuff. If you’re willing to let a performer touch the mic and hold a guitar, then you should be willing to do it yourself (or at least the potential of a lawsuit may inspire you a bit).

Hold the strings of the instrument and touch the mic gently with your finger, and work your way up to a your way up to a solid grab of the mic.

If you measure 0 volts and get no buzz from touching the strings, then the mic is quite likely going to be shock-free.

The main purpose of this step is to prepare you for the next one.

4) The last and final proof is to do as the performers will do themselves: put your lips to the mic while holding the plugged-in instrument.

Feeling Electricity
I’ve been called on many times over the years to resolve shock problems in a wide variety of situations.

Once, at a well-known Hollywood nightclub, a performer refused to play, swearing she was getting shocked by her vocal mic - but the AC meter consistently read 0 volts.

It turns out that it was the 48-volt phantom power going to her acoustic (and active) direct box, combined with a poorly grounded snake. AC metering showed no potential, because the voltage was DC.

I replaced the active direct boxes with passive ones, and then while she watched, licked the mic while holding her guitar. This reassurance was convincing enough to save the show, although she wanted a different mic!

I can already feel the backlash of those who will shout unsafe practices and not testing electricity with your own body. I agree wholeheartedly.

However, my point is that if you don’t trust that a setup is safe - so safe that you will subject yourself to the same situation you put performers in - then get someone qualified that knows what they’re doing and is willing to stand behind their work.

The consequences are far too serious, folks.

Dave Rat is the co-founder and owner of Rat Sound, a leading sound reinforcement company based in California.

With Live Sound, You Can Make Anyone Sound Good

A free subscription to Live Sound International is your key to successful sound management on any scale — from a single microphone to a stadium concert. Written by professionals for professionals, each issue delivers essential information on the latest products specs, technologies, practices and theory.
Whether you’re a house monitor engineer, technical director, system technician, sound company owner, installer or consultant, Live Sound International is the best source to keep you tuned in to the latest pro audio world. Subscribe today…it’s FREE!!

Comments (3) Most recent displayed first
Posted by Mark Phillips  on  05/13/10  at  04:22 AM
I agree with Frank - good solid stuff but a bit confusingly expressed in parts. One way of achieving that common ground in smallish venues, where there's a single desk mixing the monitors as well as FOH, is to run a fairly beefy-gauge power cable with the snake in order to power the desk (& its associated gear) from the same stage supply that's being used by the backline. Using a good heavy gauge of power cable isn't because the mixer etc needs a lot of power, it's to keep its grounding conductor resistance low (especially if the cable has to be fairly lengthy) - essential for safety. Alternatively, run a standard power cord and a separate beefy ground-wire with it (but connecting this at the two ends in a suitably safe & reliable way can be quite problematic).
Posted by oliver  on  11/01/09  at  01:17 AM
thanks for the info. it help us o lot.. we encounter this problems very often.
Posted by frank  on  07/22/09  at  01:54 PM
My apologies. I read, and re-read the first 10 paragraphs of your article before I figured out what you were saying. This is SUCH an important subject for ALL, including roadies and weekend warriers, that this needs to be written so it is crystal clear on the first reading. Sorry, it is not. I'm not an EE but I cared enough to sort out what was being said - many who need to understand will have their eyballs rolled into their head by paragraph 3. When you start in on "...shortest snake distance to the stage use the same AC (electrical alternating current) ground as the backline power." and then follow up with "... backline power should come from a circuit that shares a common close proximity ground with the “close” console.". Huh? I'm guessing this is not an issue (generally) in a small club, but in locations where the power distribution is complex and decentralized, that can be a problem. You never mention how one can determine a "close proximity ground". Hell, most of the time (again, small clubs) one can't tell if therte is one circuit or many involved. Your message is absolutely on target - I just don't think too many folks can decipher it, or apply it to their situation. Again, my apologies.
Commenting is not available in this weblog entry.

Audio Central