Star 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 DJ 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, PA systems, kitchen or bar equipment, etc.) drawing power from the AC line. There can be momentary sags, power spikes, overvoltage 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 gear 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 disk, it could alter the data being written or worse case, damage the drive.
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 supply 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 live 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.”
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.) Overvoltage 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 overvoltage condition.
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 ground lines, and within audio circuits a lot of stages (like preamps) use ground as a reference. A high-gain circuit like a mic or phono preamp can pick up this noise and amplify it. Fortunately, proper AC line filtering can often reduce noise by several dB. 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 filter 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 amp surges. Other protection devices will often clamp at 300V or more, which doesn’t provide a suitable safety margin.
The way this device handles extreme voltages is by constantly monitoring the incoming voltage, and tripping a relay 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 independent 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 reduction is often enough not just to be measurable, but audible.
Furman's exclusive SMP technology provides the highest level of surge & spike protection available. LiFT offers AC power filtering to ensure clean power for unequaled audio & video clarity. Furman’s Extreme Voltage Shutdown (EVS) protects equipment from sustained over-voltages.
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 overvoltage 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.