More Power To You!

Ask any working band what's the most important thing they need for a good show, and they'll likely name off a myriad of items, substances, or mental states. And while something can be said for all of that, they'll likely miss something much more basic.

Namely, electrical power. 

Electricity...juice, power....whatever you call it everything from your vintage Marshall to your modern PA system needs it. We don't think about, because most of the time we just plug in and it works. But like the liquor you get from the bar...it can vary wildly in quality. And sometimes, how you plug everything in can make a difference as well.

When going into a new venue (or one I haven't played in a while) the first thing I do is assess the power situation. The things I want to know are: 

  - What outlets are live and wired correctly
  - What outlets are on what circuit breakers.

The first is pretty simple if you have an outlet tester like we described last week. The second is a little more challenging, but with the proper tool can be accomplished. This is where I break out the trusty circuit sniffer.

This device is actually sold for the purpose if identifying what breaker controls an outlet (and that's a handy thing to know if the breaker panel is accessible). But what I'll use it for is to figure out what outlets are on the same breaker. For the purpose of finding shared outlets, just plug in the transmitter and go around to different outlets with the "sniffer". If it beeps, the two outlets are on the same circuit. No beep...you've found a separate circuit.  Quite the handy thing to have...it will set you back about $40 at Lowes or Home Depot.

Electrical codes (for the most part) say you can have up to 4 outlets on a single breaker. What we want to do (at a bare minimum) is to try to find at least a couple of different circuits...especially if you're carrying any appreciable amount of lighting. The idea here is to get your sound on one breaker and the lighting another.

The advantage to doing this is two fold. First, you're more likely to trip a breaker with a lot of lighting than you are with your sound gear (unless you're just carrying an insane amount of both). If you do blow the lighting breaker, you don't stop the show completely.

Second, lighting tends to be more of a noise maker as far as the power line goes (it's referred to as Conducted Emissions in UL speak). Keeping your sound on a separate circuit helps keep some of this garbage from coming out of your speakers. We'll talk more in a bit about electrical power quality. For now, we're more concerned with quantity.

Grounding is one of those things that everyone has heard of, knows it's important, but really can't explain. There have been volumes written on the subject, and there can be some really hairy mathematics associated with the principles. If you want to know that stuff, it's out there. However, this discussion is all about putting a show on...not a math lesson.

A functioning ground performs a couple of important functions for us.

• In the event of an internal short in a piece of gear, it gives the current a return path other than you!
• It gives the noise, buzz, and hum that your cable shields pick up somewhere to go besides your amp.

The first is an obvious safety issue. This is why you've always heard that you shouldn't defeat or remove the ground pin on an AC plug. I know, this is where you tell me "...but my stuff hums if I don't do that." We'll talk more about that next time, but for now know that the reason you have a hum is because you have multiple ground paths and you have violated the cardinal rule in audio system grounding:

Ken's Road Tip #3 - Though shalt have one and only one path to ground.

  

Some clubs and venues have the power thing figured out. They will have a few dedicated circuits on stage for the bands use. Where you have to be careful is in those venues where bands were an after thought. If there are outlets on the stage area (ie; corner of the dance floor), it's quite possible they were run from the beer cooler, air conditioner, or the signs on the outside of the building (I've seen this one first hand). While your sound checking, listen to your gear for changes in sound quality, hums or buzzes that come and go, or any other gremlins that might plague your performance.

Of course, short of carrying your own power distribution system and pulling your power from the electrical service entrance (this is how we did it when we were carrying 64,000 watt lighting rigs), then you're at the mercy of the club wiring. The best thing you can do it make sure you have some decent amount of power conditioning/filtering between your equipment and the outlet.

Lets talk about what constitutes "decent" power conditioning. A decent power conditioner will provide a path to ground for noise that is on the lines prior to getting to your gear. It will also function as a clamp for any high voltage spikes that come along. Spikes...I've seen them as high as 300 volts on a 120 volt line. They happen when motors or compressors (the refrigeration kind) start and stop. They typically only last a fraction of a second, but the detrimental effects are cumulative. You want the conditioner to take the brunt of this abuse...not your gear.

  

A "decent" power conditioner is not one of those strips you get for 3 bucks at the check out line at Walmart. Those things might have some clamping in them, but they're typically so slow to react that the majority of the spike gets through before they kick in. Nope, this is one of those times where you get what you pay for.

Personally, I like the power conditioning gear from Tripp, Furman (not the RackRider stuff...it's crap unless you rebuild it), APC, and Monster. Whether you get the rack mount stuff or the power strips, make sure that you've got something protecting your investments.

Here's something that doesn't get mentioned much...power conditioners wear out! Yep, you read that right. Remember when I said that the damage from spikes adds up over time? Well, there's a component inside power conditioners that absorbs these spikes (it's called a "varistor" if you're curious) that does break down over time.

So how do you know when it's past it's prime? Some of the better conditioners have an indicator to tell you. For my stuff, I have the ability to check it on a test bench (which I do twice a year). For everyone else, I would recommend replacement every 5 to 10 years or if your gear has gone through a major electrical event (noticeable power surge, nearby lightning strike, etc). It's a lot cheaper to replace a couple of hundred bucks worth of power conditioners than it is a few thousand dollars worth of gear.

With more and more gear being essentially dedicated purpose computers, it's getting more and more important to deliver clean power to your equipment. One thing we haven't talked about is voltage regulators. These are a different animal from conditioners, in that their purpose in life is to make sure that you actually have 120 volts delivered to your gear...not 105 (less than optimal), or 140 (really bad).

Regulators actually turn the voltage up and down as needed to keep a consistent output. The really good ones use a multi-tap transformer, but they can be heavy and are expensive (typically north of $500). The less expensive ones perform the function using solid state devices, but the downside is they introduce their own noise. If you're carrying any significant amount of digital equipment (keyboards, mixers, etc) you owe it to yourself to look at adding voltage regulation to your set up. They even make a difference with tube amps, and help cut down on that "man...my amp sounded great earlier...what happened" syndrome.

Next time, we'll wrap up our discussion on power by going into more detail on grounding and the potential issues (there's a pun in there) that you can run into. And we will attempt to answer that age old question, "Why is my mic shocking the $#!+ out of me?"

Until next time, keep the meters out of the red!

Ken

Ken Carver has been a musician and performer since the early 70's, and involved with live music production since the mid 70's. He worked for 15 years as a broadcast engineer, building numerous studios and transmitter sites around Texas. He's also worked in Critical Care Communications for the medical industry, R&D for an automated lighting manufacturer, and owned Project Lighting & Sound in the 80's. He currently heads up an R&D Hardware Technician Team at National Instruments in Austin, and still performs on the weekends in the Central Texas area. You can reach Ken at kcarvertx@gmail.com