Last month, we discussed the concepts of power requirements, and ensuring that the in-house service is up to the task of powering your P.A. system. This time we’ll look at some specific power distro products that can help make life on stage a bit easier.
Easy As One Two Tree
Any power distro has a few basic requirements that include (1) ensuring that enough current is available to power the gear, (2) keeping the power supply clean so that no audible noise is generated by the presence of electric motors, fluorescent lighting or lighting dimmers and (3) that the system meets electrical code to maintain safety. We’ve already visited the first item on the list, and the second is fairly simple to address: no motors, lighting, dimmers or fog machines should be using the same distro as the audio gear. In terms of safety, DIY power distros should be considered a “no-no.” Even if you are a licensed electrician capable of creating your own distro system that is perfectly safe, a mishap could make you responsible for property damage or physical harm to another person. So we’ll stick with UL-approved, commercially-available products.
Regarding power-up sequence of audio gear: audio amplifiers typically draw heavily from the AC supply when they are fired up, due to the fact that this is the time when the power supply capacitors charge. It’s probably a bad idea to use a single switch to turn on three or four monster amps at the same time — the temporary AC demand could blow a circuit breaker. Some distros take this into account and provide the ability to create a timed “sequence” for turning on the breakers [On a related topic, some digital effects do not like being switched on and off via power strip, and may behave erratically. Use the power switch on the device instead].
Plug Me In Already
So what should you do when you need a safe way to supply electricity to multiple power amplifiers and/or other audio gear? Here are some suggestions.
Peavey Distro (peavey.com) is a rack-mounted power distribution unit featuring six independent 20-amp AC circuits. Each circuit has its own magnetic breaker that also serves as a front-panel power switch. The Distro is intended to be housed in a rack along with the power amps, and eliminates the need to find an individual outlet for each amp every time the system is moved. Since all amps share the same ground, the ground-related noise issues that often arise when amps are connected to multiple AC services are reduced.
Power is supplied to the Distro from a (kitchen range-style) NEMA 14-50 socket that typically would be rated for 50 amps at 240 volts; the unit includes the requisite cable and plug. A pair of front-panel lamps indicate “feeder hot” in accordance with requirements specified by the National Electric Code.
Note that just because the Distro provides six 20-amp circuits does not mean that you can load it up with gear requiring a total of 120 amps. It’s rated to deliver 80 amps maximum, but allows you to split up the load, perhaps connecting the house speakers (or amps) to one duplex, monitor system gear from another and backline from a third.
Gear Box Pro Ltd. (gearboxpro.com): offers a variety of rack mount portable power distro products. Their SLP-233 (Slim Line series) is a 220-volt/30-amp, single-phase power distribution unit that’s two rack spaces high and less than four inches deep, enabling it to be mounted in a rack on rear rails behind gear so that you can save rack real estate. Four 20-amp circuit breakers on the front panel feed four circuits on the top of the chassis, with parallel-connected duplex receptacles on the bottom of the box. This enables you to connect AC cables at 90° to the power inlet connector, leaving the back of the unit clear of electrical plugs and cabling that might otherwise obstruct cables connected to gear mounted opposite the rear of the SLP-233. Power is supplied to the SLP-233 through a NEMA 15-30 receptacle on the front panel; the front also features status indicators for the feeder supply.
Gear Box Pro’s PCD series takes a slightly different approach, distributing AC via powerCON connectors. The PCD 238 is two rack spaces high with all components mounted on the front panel, so you won’t need access to the rear panel. The PCD 238 uses a NEMA L15-30 power inlet to feed six 20-amp circuit breakers. Instead of the typical Edison outlets, these breakers feed powerCON outlets (though a paralleled duplex outlet is provided for convenience), which can be used to distribute power via a variety of products such as the Power Cube® 4E. A modern take on the old quad box, the Power Cube 4E (roughly 6x6x2 inches) can accept AC from the PCD 238 via powerCON cable, offering two duplex receptacles, a powerCON thru connector and a power indicator light. The powerCON inlets and outlets are parallel connected, supporting a combined maximum electrical load of between 12 and 16 amps depending on the rating of the supply cable employed to make the connections. Multiple Power Cubes can be daisy-chained, and the 4E is available in right or left handed versions. No more wondering “…is this extension cable getting power?”
Whirlwind Audio (whirlwindusa.com): Designed primarily for use in amplifier racks, the Power Pack modules in Whirlwind’s Power Link line convert a multi-phase input into breakered, branch circuits to feed individual amplifiers. All are fully enclosed, UL-listed devices. The company also makes a series of NEMA twist-lock boxes that break out into multiple circuits with 20-amp Neutrik powerCON connectors as well as a modular system of in-line 8-outlet Edison outlet strips that link together via powerCON cabling, creating single-circuit AC distribution chains.
In Short (Pardon the Pun)
There are a few things we should mention regarding power that may seem like common sense, but then again…
When visiting unfamiliar venues, make sure that the AC service can actually supply the amount for which it has been rated (and has not kludged together by a DIY’er).- Carry a pocket outlet tester so you can ensure that club wiring was done correctly.
- Be aware of the fact that retractable extension cords on a reel should be completely unwound before use, as they create heat. In fact, if you look at the specs carefully, you’ll often find that they have different load ratings for wound and unwound operation.
- Never remove the ground pin on the AC connector of any electrical device. The ground pin is there to protect people and wiring from harm in the event of a system failure. Remove it and that protection is lost. If you have ground hum in an instrument line, find another way to fix it, such as a DI with an audio ground lift or an isolation transformer.
- Avoid sticking your tongue into a circuit breaker box. “Just sayin...”
