What's In Your Tool Box?

If you're a musician who uses electricity and cables in the course of your performance, then you need to read this post.  

There are a couple of basic facts in life that directly affect you and your performance:

 - Cables are the the weak link in most audio systems
 - There are a lot of ways for the electrical system in a building to be screwed up

Let's talk about the power first.  In the coming weeks I'm going to do an article on AC power, grounding, and other related topics.  But for now, this is about your safety and the well being of your equipment.  

The main thing to remember is A Faulty Ground Can Kill You.  Period.  Even the "famous" guys aren't immune to this.  One of the most famous incidents was in 1972 when Les Harvey of the Scottish band Stone The Crows was killed on stage when electrocuted by a microphone.  Gary Thain of Uriah Heep was severely electroducted in Dallas in 1974 and never really recovered.  Ace Frehley of KISS got a 220 volt jolt due to a ground fault between his guitar amps and stair railing on the stage set of the Destroyer tour in the late 70's (and yes, that was the inspiration for his song Shock Me).

So, how do you know if that cruddy outlet you're plugging your PA system into is wired correctly?  You spend $5 and get yourself an outlet tester:

That's what I live for...two yellow lights!  Buy plugging this in, I know that:

• The outlet is actually functioning (it's no fun troubleshooting equipment when the problem is the outlet is dead).
• The outlet is wired to the correctly polarity (more on that in our AC power article)
• Most importantly, we have a functioning ground

Knowing that the ground is intact means that the noise and hum that gets on the shields of our cables has a place to go.  But more critical is that in the event of an electrical fault in our equipment, the AC current has a place to go besides through us!  

You can pick these things up at home improvement stores (Lowe's, Home Depot).  Think of it as a $5 life insurance policy.  I check every outlet at a new venue before plugging in anything.

And then there are cables.  It's not "if", but "when" are they going to fail.  Buying (or in my case building) quality cables helps, but at some point someone is either going to pull the wire from the connector or roll the road case with all of the mic stands over one.  

So if you have more than a few mic / speaker / instrument cables, you should own a cable tester.

Plugging in this mic cable, I can see that not only are all of the individual wires are good, but it's also wired in phase (yet another future topic).  My long time favorite has been this Behringer CT100, and it's the best $25 I've spent on troubleshooting tools.  It does XLR, 1/4", 3.5mm, RCA, and MIDI.  It also has a latching function on the indicators to catch intermittent shorts or opens.  Other people make 'em (Peavey, Nady, Hosa)...this just happens to be the one I have.  The one thing it's lacking is being able to test Speak-con connectors, so I'm probably looking at getting one to do that since those connectors are becoming a lot more common now.

Keep in mind that a balanced XLR mic cable can have 1 conductor open and still function...just not as well.  You loose your noise cancellation, the signal level drops, and you can have problems with phantom power if you're using that.  So, a few times a year I get the band over to the house and we go through and check all the mic cables.  While we're at it, we run them through a damp bar rag to clean who-knows-what off of 'em.  It's call Preventive Maintenance...and there's yet another future topic.

This is a "luxury" item to a lot of people, but if I've got any question about the power in a building I'll break out my Digital Multi-Meter (aka DMM).

The outlet tester can tell me if an outlet is wired correctly, but it doesn't actually tell me the voltage at the plug.  If you're working where there's permanent power, it's pretty safe to say that the line voltage is going to be around 120V (but not always...more in a moment). However, if I'm playing an outdoor show where we're on generator power, I always check it! I saw first hand several years ago an improperly connected generator take out 2 Mesa Dual Rectifier amps (about $4000 worth of amps up in flames).  If someone had taken 2 minutes to check, they would have seen that the "120V" outlets were actually wired to 277 volts!

Sometimes you run into a situation where you have the opposite problem...low voltage.  There's a club in south Austin I used to play where my digital amp would actually reboot, and the other guitarist's tube amp just sounded bad.  We measured the voltage coming out of the outlet, and found that when the walk-in cooler compressor kicked in, the outlet dropped to 87 volts!  We found another outlet to plug into (and I started carrying a voltage regulator after that).

A DMM is also nice for checking if a wall wart power supply is working or not.  And, you can use it for finding faults in cables (although the cable checker above it a lot easier to use).  The one above is a pretty fancy one that I keep on the bench for troubleshooting.  You can pick up a basic model for about $15 when you get your outlet tester.

You should be carrying a lot more than this in your tool box, such as tools to work on your instrument, batteries, fuses, strings, picks, bail bondsman's phone number, etc.  But these are gadgets I see a lot of folks not carrying.  It's not a lot of money, but they sure lower the aggravation factor!

Since we've kind of started the discussion about AC power and such, we'll continue that next time.  We'll talk about grounding...that's a term that everyone throws around, but I find that very few people actually understand the concept of.  I'll try to take the hyper-tech out of it, and just relate the points that are important to us as musicians and performers.  We'll also talk about balancing your power loads, and I'll show you another gizmo that I find very useful in new venues.

Until then, 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