Don’t Kill The Artist

From Roadiepedia

Jump to: navigation, search

HEAD: Don’t Kill The Artist! DECK: Electrical safety on stage

By Dave Rat

http://ratsound.com/mwiki/images/7/76/RatTales0106_Proof1.pdf

Although the musicians we work with tax our patience at times, and occasionally unfriendly thoughts about them cross our minds, I seriously doubt that watching them fry from high voltage is something any of us would want to be responsible for.

With that in mind, here are some basic precautions and tests to reduce if not eliminate the possibility of electrocuting our musical friends.

Let’s start by stating that it is important that the mixing console with the shortest snake cabling distance from the stage utilizes the same AC ground as the band’s instrument amps (the backline).

You want the backline and close console grounded together really well. Do not depend on unknown lengths of wires, hidden in walls, to give you reliable grounds. Use outlets that are physically grounded together by short wires or solidly connected metal boxes.

Each microphone is grounded to the mixing console by the ‘pin 1’ of the XLR connector. The mixing console then grounds the XLR pin 1’s to the AC ground. All microphones have an internal connection between pin 1 and the casing of the mic, for ground shielding. The console closest to the stage should not be pin 1 lifted as it provides the critical shielding ground to the mics and that keeps the hum down.

Eliminating hum issues in sound systems often involves lifting various AC and audio grounds. Without getting sidetracked into system grounding techniques, I want to stress that the band backline and at least one console must be grounded if you value your musicians lives.

One of the more difficult things to get a handle on is the grounding and safety of the backline gear itself. Unlike a sound system, it’s often something that you often have little or no control over.

The affinity over “vintage” gear combined with multiple amp setups can often present an even more unwieldy situation. Though I can’t cover all possible configurations, here are two rules of thumb that help keep musicians safe:

1) Whether there is one or multiple guitar (or bass) amps all connected together, at least one piece of gear in the signal chain must be AC grounded, preferably the one that the guitar (or bass) plugs into.

2) When presented with a “vintage amp” that has a non-polarized ungrounded plug, pay extra attention to how it is plugged in. At the very least mark the plug and actually, it’s best to replace it add that ground! The musician killers are the AC plugs that don’t have the “fat” and “skinny” flat blades - both blades are “skinny.” On all modern ungrounded plugs the “fat” blade is neutral and the “skinny” blade is hot, therefore making sure the plug cannot be reversed in the outlet.

PESKY GREMLINS I was on tour with a well-known band and everything was going very smoothly until out of nowhere, bam! The singer takes a “blue light special” from the mic right on his lips.

Dazed, the poor guy struggled to finish the song without getting shocked again. It only happened that one song and the rest of the show was fine. The stage techs investigated, but to no avail. A few days later, it happened again.

So I spoke with the tech that religiously tests this guitar rig for shock prior to every show and he was at a loss as to the cause.

After further evaluation, we were able to determine that the guitar player, mid-tour, had purchased a small vintage amp (with two-prong old-style AC plug) from a pawnshop and he only played it for one song a night.

Before each show, the guitar tech would dutifully touch the guitar strings to the mic, and if it buzzed or sparked, he would flip an AC polarity switch on the back of the amp. After soundcheck ended he would go to dinner. Then each day the support act would unplug the vintage amp and use that AC box for their guitar rig.

After their set, they act would put the AC box back and plug in that little vintage amp. Some days it would get plugged in one way, some days the other way, and the problem was that when the plug was reversed, 120 volts would show up between the guitar strings and mic.

I just put a three-prong, grounded plug on the amp, and though it’s no longer “vintage,” it’s no longer trying to kill our beloved performer.

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 question or 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 be safe, but if there’s a hardwired spare, it must be checked. 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 between the mic and any metal that the performer may come in contact with. You want to see less than 1 volt or so, and be sure to check for both AC and DC voltages.

2) Turn on the guitar rig and the monitors and with the guitar plugged in, touch the guitar strings to a bare metal part of the mic.

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 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 with your finger, then work your way up to a solid grab of the mic.

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 was threatening to cancel the show, 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 asked for a different mic!

I can already feel the backlash of those who will shout unsafe practices and not testing test 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.

Personal tools