Protection & Regulation
Surges are spikes in power that last three nanoseconds (billionths of a second) or more. Spikes, meanwhile, are differences in voltage above the normal line level that last about two nanoseconds or less. A quick increase in voltage may not seem like much trouble, but it can put extra strain on components or even damage/destroy them.
Surge and spike protectors are designed to mitigate the problems, reducing the higher voltage on the hot leg of the circuit. Some also include sacrificial parts (like fuses) that get destroyed – better to blow up an inexpensive fuse than an expensive amplifier or mixer.
Rack-mounted protectors are popular in live production. On most units, the outlets are located on the rear and the power switch and a possible courtesy outlet are placed on the front. Many of these units also have dimmable lights on the front panel that can illuminate the faces of other racked gear, allowing easy adjustment in the dark.
Power conditioners (a.k.a., line conditioners) distribute the proper voltage to their outlets. They regulate the incoming power within the specified output range by increasing lower voltages or decreasing higher voltages, and they normally also contain spike and surge protection circuitry and noise filtering. The IEEE (Institute of Electrical and Electronics Engineers), NEMA (National Electrical Manufacturers Association) and others have standards for power conditioning.
The Furman PL-PRO DMC is a 20-amp unit offering a multi-stage protection circuit and an extreme voltage shutdown that can help save gear.
A UPS (uninterruptable power supply) is outfitted with a battery to keep the juice flowing to the gear in case of an AC power outage. In normal use, wall power charges the battery and an inverter circuit changes the battery power to AC. If the wall power goes out, the battery power can last for a specified amount of time. These units, also available in rack-mount versions, aren’t likely to get you through a gig but will do the job for shorter power outages, and they also provide added time for safely powering down audio electronics and computers.
Power sequencing is another popular tool in pro audio. Sometimes electronics need to be turned on in a specific order, such as a console and then amplifiers, and a power sequencer makes this an easy one-button process. (The same for powering down components.) Timing is fixed on some units, while on others it can be adjusted.
Some also allow multiple sequencers to be joined together, and a few can be connected to a network and controlled by a master program.
Remember, every gig starts with power. And it can also end that way, sooner and with possible damage, if best practices aren’t followed.
Editor’s Note: Both Craig and fellow LSI contributor Mike Sokol have contributed several useful articles regarding AC power as it relates to pro audio over the past few years. Be sure to check them out on ProSoundWeb, and further, Mike heads up the AC Power and Grounding forum on the Live Audio Board at PSW containing even more information as well as the ability to get informed answers regarding key issues.