By Full Compass LiveStar Trek fans are familiar with that moment when Scotty the engineer, upon being asked to make the spaceship do something impossible, says "I can’t give you any more power, Captain!" Although doing a mobile DJDefinition:
DJ (Disk Jockey): 1. Traditionally applied to people who played recorded music on the radio or at events. 2. Artists who perform using any combination of pre-recorded music, samples, turntables, and musical instruments. gig or being on stage may not present the same hazards as avoiding Klingons intent on destroying you, there can still be a plethora of potential power problems.
Many of these issues are inherent in venues because of the number of high-current devices (lighting, PADefinition:
(Public Address) A sound system intended to provide audio coverage to large groups of people. systems, kitchen or bar equipment, etc.) drawing power from the ACDefinition:
(Alternating Current): Current whose electrical flow alternates between positive and negative quadrants, and whose magnitude varies periodically. Alternating current is used in most commercial power transmission, and is also the basis of audio or video signals. line. There can be momentary sags, power spikes, over-voltageDefinition:
Also called electro-motive Force (EMF). The "charge potential" or pressure of electrons that causes current to flow in a circuit. conditions, and "dirty" AC lines that carry noise. We can’t help but notice catastrophic power failures, like blackouts. However, there are a less obvious issues that can affect not only a performance, but impact the life of your gearDefinition:
Musical or performance equipment. and cause unreliable operation.
There’s been much written about how an X-class solar flare could fry a lot of our microprocessor-controlled gear—and that’s a spike coming from 93 million miles away! Much of our computer gear is susceptible to spikes; as just one example, if a heavy spike hits a hard drive while writing to diskDefinition:
A storage medium, typically applied to magnetic-based media (e.g., floppy disk, hard disk)., it could alter the dataDefinition:
Information used by a computer in order to arrive at a decision. Although this is a plural term, it's often treated in the singular. being written or worse case, damage the drive.
Spikes
Power spikes—momentary, high-voltage transients–don’t always kill equipment outright, but instead chip away at component reliability until some parts eventually fail. This is because many electronic components (like capacitors) have specific voltage ratings, and exceeding them stresses their internal structure and can shorten their lives. Gear that shaves power supplyDefinition:
A device (internal or external to another device) that provides power for active circuitry. Can be AC, DC or battery-powered. quality to the minimum necessary in order to reach a price point are most susceptible to these kinds of issues. If the power supply isn’t protected internally–and any protection that’s there is probably minimal–then it needs beefier, external protection.
Unfortunately, the inexpensive consumer-oriented surge protectors (and even some expensive models) you find at hardware stores don’t come close to meeting pro audio’s demands. They often require a very high voltage (the clamping voltage) before protection kicks in, and with less expensive models, the spike suppression circuits essentially sacrifice themselves to protect your gear. This can happen after a major spike, or multiple smaller spikes, and then leaves your gear unprotected. Once the surge protector is damaged, you need to either repair it, or buy a new one. This is just one of the reasons it became apparent that voltage protection for liveDefinition:
Live broadcast of an event or program without substantial delay or editing. use needed to be designed for zero down time–after all, whether there’s been a major voltage spike or not, “the show must go on.”
Extreme Voltages
Even if a venue is wired to code, problems can happen like an intermittent neutral connection, accidentally plugging into a 208V or 240V line intended for air conditioners and other heavy-duty appliances, or voltages induced into the AC line from a lightning strike a considerable distance away. (No protection device can survive a direct lightning hit–but if there’s a direct lighting hit at the venue, you probably have more important concerns anyway.) Over-voltage conditions can, in fact, kill gear, not just eat away at it, so it’s important to shut down power going to your equipment immediately in case of an extended over-voltage condition.
Noise
People don’t always associate noise with power issues, but there can be a measurable correlation. Some electrical equipment is "dirty," and puts noise on the AC line. This noise can travel along groundDefinition:
A common zero-volt potential connection, commonly used for both electrical noise control and safety, and usually connected to the ground of the earth through a spike, plumbing, or electrical wiring that leads eventually to an earth connection. AKA: Earth. lines, and within audio circuits a lot of stages (like preamps) use ground as a reference. A high-gainDefinition:
The amount of amplification provided by an amplifier circuit, expressed in dB or numerically as in "3X" = "3 times". circuit like a mic or phonoDefinition:
Short for phonograph. preamp can pick up this noise and amplify it. Fortunately, proper AC line filtering can often reduce noise by several dBDefinition:
1. A deciBel is a logarithmic ratio between two quantities, and is a nonlinear measurement that mimics human perception. 2. A unit expressing sound levels relative to a nominal level just audible by the average human ear, and equal to 1/10th of a Bel. 3. (slang) Database.. While you may not notice this onstage when the crowds are screaming and going wild, the difference can be very apparent in the studio.
Power Conditioning Devices
At the hardware store level, whole-house protection circuits are a step up from the barrier-strip-with-the cheap-varistor option. However, stage use has far different requirements than protecting a house. You don’t have the option of a permanent installation, so the protection has to be part of your stage setup. Few traditional protection devices take noise into account, and some of them actually add noise because the filterDefinition:
1. (audio) A circuit that reduces certain frequencies, e.g., a low-pass or high-pass filter for audio. See also: Equalizer. 2. (optics) reduces certain color wavelengths or polarizations. circuits they use have resonant peaks. Music gear can also be more delicate than appliances like refrigerators and HVAC (heating/ventilation/air conditioning) systems.
Furman’s PL-PRO DMC is a good example of power protection designed specifically for stage and studio use. Instead of using spike absorbers that fail after a few spikes, the PL-PRO DMC uses multiple stages of protection. This distributes suppression over several devices to avoid putting any of them at risk. The main benefit, aside from better protection, is that if there’s a major spike there’s no downtime required to replace the spike suppression element. There’s also a lower-than-usual clamping voltage of 188V, which remains in effect even with 6,000V peaks and 3,000 ampDefinition:
Abbreviation for either Ampere or Amplifier. surges. Other protection devices will often clamp at 300V or more, which doesn’t provide a suitable safety margin.
Furman’s PL-PRO-DMC Power Conditioner features Furman’s revolutionary Series Multi-Stage Protection (SMP), Linear Filtering Technology (LiFT), and Extreme Voltage Shutdown (EVS).
The way this device handles extreme voltages is by constantly monitoring the incoming voltage, and tripping a relayDefinition:
A mechanical, electrically-controlled switch. above 140V to shut off all power until the over-voltage condition stops. As extra protection, you then need to do a manual reset once you’ve determined the over-voltage condition has ceased. Note that the PL-PRO DMC also protects against under-voltage conditions (under 90V), which can be just as damaging to some gear as over-voltage conditions.
As to noise, this is another consideration that’s unique to devices intended for stage (or studio) use. Furman’s filter design is independentDefinition:
A electrical circuit that is separate for lighting control, or a light board channel independent of other controls or programming. of ground contamination, so noisy ground lines can’t get into your gear. Furthermore, power is separated into two isolated banks to minimize inter-component interference. The amount of noise reductionDefinition:
A technique for reducing noise in recording or transmission systems. Single-ended noise reduction systems use filtering to isolate the noise, and expand this signal downward using downward expansion. See Expansion and Downward Expansion. Double-ended systems use symmetrical compression and expansion. See Compansion. is often enough not just to be measurable, but audible.
Furman’s exclusive SMP (Series Mutli-Stage Protection) technology provides the highest level of surge & spike protection available. LiFT (Linear Filtering Technology) offers AC power filtering to ensure clean power for unequaled audio & video clarity. Furman’s EVS (Extreme Voltage Shutdown) protects equipment from sustained over-voltages.
Applying Protection
Any stage situation benefits from power protection, but mobile DJs arguably have the most to gain because the venue, power, and conditions change constantly, while lighting draws lots of power that can cause AC power instability. Here, filtering is important to reduce noise, but of course spike and over-voltage protection matter as well. Because mobile DJs often carry their own amplification systems, make sure that whatever unit you use has enough protected outlets for all the required gear, and can handle the needed amount of power. For example, the PL-PRO DMC’s current rating is 20 Amps—more than enough for a typical mobile DJ setup—and has nine AC outlets with full protection.
In any case, when you consider your investment in gear, power protection isn’t just about salvaging a performance but also providing insurance. You might be surprised at how your gear seems to work just that much more reliably, and last just that much longer, once you start feeding it a diet of the purest possible power.
