If you’ve read the survey we’ve been running here on ProSoundWeb (Haven’t taken it? Please do!), you’ll discover that 70% of the musicians and sound technicians surveyed have been shocked by their mics, instruments and sound systems. 

What follows is the second 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. 

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.

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. 

Just the Facts
In Part I of this No~Shock~Zone Stage series you learned what voltage is and a bit on how it’s measured. In this article we’ll cover how to use a basic digital voltmeter to measure any power outlet or extension cord for proper voltage.

The reason this procedure is so important is that sometimes venues do crazy things with power outlets. For instance I was teaching a seminar last year in a “gymnatorium” and plugged in my little demo rack along with my RF headset receiver.

As I was getting ready to flip the switch on the Furman rack distro, I noticed the built-in voltmeter was pegged to the right of the 120 volt scale. Luckily, I didn’t go further and did not flip on the switch that powered the full rack.

But unluckily for my RF receiver, it was ahead of the Furman power switch so it was already “on” and burning quite brightly for a few seconds. A quick meter test on the power outlet confirmed it had been jury-rigged for 240 volts, even though it was a standard NEMA-5 “Edison” outlet, which should always be wired for 120 volts.

The janitor told me that was his “special outlet” they had rewired for his 240-volt [floor] buffer. But it should have had a 240-volt plug and outlet, not an Edison outlet modified for 240 volts. My bad for not checking.

My RF receiver was toast, but all the rest of my gear was fine. Live and learn….

Shake & Bake
Remember when you were a child and first started to help with cooking, and there were all sorts of measuring devices and abbreviations to take into consideration?

There was a Tablespoon (Tbsp), teaspoon (tsp), Ounce (oz.), with 8 oz. in a cup, and so on. And you better not get your tsp and Tbsp mixed up or bad things would happen to your cake.

The same types of rules apply when you’re measuring any electrical values. You just need to know how to use a few electrical measuring tools and then you’re ready to test your stage power.

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