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DJ Audio and Lighting Troubleshooting Tips
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There’s no getting around Murphy’s Law,
but here’s how to avoid paying dearly.
You remember Murphy. That pessimistic fellow who once said “…anything
that can go wrong will.” Sometimes he’s all too right—like when a
gremlin gets in your system and says “gotcha” right when the crowd is
singing “The Bride Cuts The Cake.” How do you avoid being a victim?
Here are some troubleshooting tips to keep Murphy from wreaking havoc on
your next event.
TOOL TIME
A tool kit is a big help when things go awry. Include a pair of
needle-nose pliers, wire snips, a couple of screwdrivers, fuses, vise
grips, duct tape, electrical tape, and light bulbs for your lighting
system. I also recommend an electrical tester of some sort, which you can
get at any hardware store, so that before you plug into that VFW outlet,
you can make sure it is wired correctly! If you know how to do continuity
tests, then a continuity checker, which checks for bad wires, is another
good item for your tool box.
SPARE ME
Faulty wires and cables cause most problems. You should have at least one
backup cable for every type and style of cable in your system. But
sometimes things go wrong that you can’t fix on the spot. This is why
it’s so important to bring backup equipment. If you use wireless,
don’t leave home without a spare wired mic also. If your disc player
quits, a Sony Discman can save the show. A Gemini PMX-7, for example,
sounds great and fits in the bottom of your toolbox, just in case your
mixer goes on the blink.
If something big is going to fail on you during a show, it will most
likely be your amplifier. Your spare should be a professional, not
consumer model. It doesn’t have to be big, but it should be as reliable
as your main amp. Lightweight amplifiers, such as the MTX P850 are an
option. Soundtech has a couple of full-sized models that will also fit the
bill. For full main amp force, check out the PLX series from QSC.
Generally an amp even half the power of your main will still be good
enough to get you out of a bind.
TESTING 1, 2, 3
What do you do if a failure occurs? Start by working backwards from your
speakers to your sources (phono, CD player, etc.). Inspect the cables,
checking for frayed ends. If one speaker channel is dead or humming, swap
the cables. If the problem moves from one speaker to the other, the
speaker is good and the problem is elsewhere, or in the speaker wire
itself. Swap the cables at the amplifier. If sound now comes out of the
speaker that was previously dead then the problem lies further up and not
in the wire.
Next, check the amp to see if it’s getting a signal from the mixer. Are
the meters moving normally? If so, then you either have a bad channel on
the amp or a bad cable. Follow the same procedure as with the speakers.
You should shut off your amp every time you change wires to avoid damaging
pops and clicks. If you determine that you have a signal from the mixer,
and the wires are OK, the problem is in the amp. If both channels are dead
or humming, but the meters on the amp are moving and you’re getting no
sound, see if the amp is in “protect” mode. Most models have built-in
protection from bad loads or short circuits. You could have a wire that is
shorting at the terminals or is frayed. If the two bare wires touch
together, that will shut down the amp.
If your mixer’s outputs are fine, check to see if the problem is
isolated to one source. If you have output on both channels from
everything but one unit, then the problem could be in the unit or its
wire. If so, break out the Sony Discman. If not, there is a problem with
the mixer.
With turntables you may have a loose connection in the tone-arm or needle.
Make sure the headshell is firmly seated in the tone-arm and that the
contacts are clean. If you are getting a nasty hum check the turntable’s
ground wires.
As for lighting systems, most of them are self-contained, so if you have
trouble with a unit, it will be out of commission with two exceptions: the
bulb and the fuse. Always spare fuses and bulbs for each lamp you have in
your system.
PREVENTATIVE MAINTENANCE
You can also use this procedure when checking your system before a gig.
Checking your wires in between gigs can reveal potential “hot spots.”
As far as your equipment is concerned, most of the checking should be done
with the system on, at low volume. Turn the gains down on the amp for best
results.
Being prepared ahead of time will definitely reduce your visits with
Murphy to a minimum.
System Failure
BE PREPARED! You should keep equipment backups (as well as other essential
items) on hand, ready to go should you have a problem. You should also
carry a toolbox that has screw and nut drivers, pliers, cutters, jumper
wires, plenty of audio adapters, fuses and light bulbs.
For the average system you should have at least one backup cable for every
type of cable in your system. The most common system failures can be
traced to bad cables. You plug them in and out, you step on them and run
over them with your hand truck. Do yourself a big favor and carry backup
cables. If you use a wireless mic, keep a wired mic handy as a spare. I
find that a Sony Discman can be your best friend when a CD player fails.
Toss one in your toolbox (carefully) along with a selection of premixed or
compilation CDs just in case your mixer should go down. As a backup, I
suggest having a small mixer available.
Now here is where things get a little bit more involvedx your amplifier.
Next to cables, the amplifier is the most common item to fail. Never skimp
on a spare amp either; get a professional model. It doesn't have to be
big, bad, and brawny, but it should be as reliable as your main amp.
Whatever you do, don't try to use a home stereo system. They are not built
for the heavy demands of pro sound. A used, professional amplifier, even
if it has half the power of your main amp, will be good enough to get you
out of a bind. After all, a little music is better than no music.
Speakers are another matter when it comes to backups. Unless you have a
large van with room for a spare set of speakers, carrying a second set
around is probably not feasible. The best thing to do is to protect your
speakers from burning out in the first place by using a compressor/limiter
or speaker fuses.
If you have extra room in your car or van, you might want to carry a spare
tweeter or midrange, as these are the most common parts of the speaker to
burn out and are small enough to put under a car seat. If you work alone
and have a problemx BE COOL! Don't look at the guests; look immediately at
your system. Begin tracing where the problem may be; it might be as simple
as you hitting the wrong button! Work as fast as you can to solve the
problem. Then when everything is running again, return to the festivities.
Quickness is of the utmost importance. Practice this at home with a
friend. Have him "cause" a problem on your system and you try to
figure it out. Pretty soon you will become familiar with potential
problems and, should it occur during a real live performance, you will
recognize it and solve the problem quickly.
If you've checked and determined it wasn't user error, you should next
check your cables. A typical sign of a bad cable is having a channel
suddenly drop out without the amp going into protect. You may also get a
hum or buzz in the system suddenly. Do a physical inspection of the cables
first. Make sure you have no frayed ends. Then start tracing your way
backwards. Start with the speakers; if you have one channel dead or
humming, swap the cables. If the problem moves from one speaker to the
other, the speaker is good and the problem is further up, or in the
speaker wire itself.
Next, swap the cables at the amplifier's output. If the problem shifts
between the speakers, then the problem lies further up the chain and is
not the wire. Move on to the amp. Make sure it is getting a signal from
the mixer. Are the meters moving like they normally should? If so, then
you have either a bad channel on the amp, or a bad cable. Follow the same
procedure for determining if you have a bad cable to check your speakers.
You should shut off your amp every time you change wires to avoid any pops
or clicks from surging through your system. If you determine that you have
sound coming out of the mixer, and the wires are OK, the problem is in the
amp. It is time to break out your spare amp.
If your mixer's outputs are fine, check to see if the problem is isolated
to one source (CD player, turntable, etc.). If you have sound coming out
on both channels on everything but one unit, then the problem could be in
its connecting cable or the unit itself. If so, break out the Sony
Discman. If not, then there is a problem with the mixer!
If you are using turntables, sometimes you may get a loose connection in
the tonearm or needle. Make sure the headshell is firmly seated into the
tonearm and that the contacts are clean. Also, if you are getting a nasty
hum out of the system, check the turntable's ground wires.
Should your microphone go bad, and you don't have a spare, you can
effectively use your headphone as a mic. It will work fine, although the
sound will not be very good. Always keep a spare headphone in your tool
kit. Keep an assortment of Adapta-Plugs on hand as well.
This is a pretty straightforward approach should you have a problem with
one channel. If both channels are dead or humming, the first place to look
is the amp. Is it getting an output from the mixer? You can determine this
if the meters are moving and the amp is on, but you get no sound. If so,
then the problem could lie in the amplifier. See if the amp is in its
"protect" mode.
Many amplifiers have this built-in; it is designed to protect the
amplifiers from bad loads or short circuits. You could have a wire that is
shorting at the terminals or is frayed. If the two bare wires touch
together, that most likely will shut down the amp. The best way to deal
with problems on the job is to avoid them in the first place. Don't try to
use the same system you use for a 50-person backyard party as you would
use for a 300-person high school prom. These are totally different gigs
which need totally different systems. If you push your system beyond its
limits, you will damage it. Don't shout in your mic, and watch those clip
lamps! (Most amplifiers have an overload indicator called
"clip." If it lights, lower the volume!) And REMEMBER! Be
prepared, and don't panic!
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