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Engineering Extra
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The Reference Room
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Wired for Sound: Steve Lampen
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| I’m the Man Who Found the Lost Cord |
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by Steve Lampen,
9.26.2007
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Steve's latest book, "The Audio-Video Cable Installer's Pocket Guide" is published by McGraw-Hill. He can be reached at shlampen@aol.com.
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Do you understand the joke in the title? The “Lost Chord” is a serious piece of music, one might almost say a hymn, by Arthur Sullivan of Gilbert & Sullivan fame. The title of my column is a British music hall joke song adopted by Jimmy Durante, the “schnoz,” here in the U.S. Of course, it should be the lost “chord” but I wrote the lost “cord,” as we’ve been talking about power cords. We’ve talked about gage size, current draw, even the melting temperature of the jacket.
One other factor you need to consider in choosing power cords is ruggedness. Most power cords, certainly the ones you get free with a device, are almost always PVC. Simple, cheap and not particularly rugged, they work fine in a protected environment, such as a rack or other permanent install.
Rubber
In you’re on the road, however, or plugging and unplugging constantly, or if people are stepping on these things, you might want to consider alternatives. Rubber, real hole-in-the-tree rubber, is extremely rugged and lasts virtually forever. There is artificial rubber, called EPDM, and similar artificial rubber-like materials made by others manufacturers. Some work well when wet, or in sunlight, or are scuff-resistant, or are very flexible.
Most of the artificial rubber compounds are “thermoset.” These compounds are “cured” (“Vulcanized”). Thermoset is set, and can’t be recycled. In contrast, plastics (correctly “thermoplastics”) can be chopped up, re-melted and made into new cable (or pop bottles, plastic bags or park benches).
If you’re a roadie or a truck guy/gal, you might want to get an example of each of these rubber or artificial rubber power cords and do some tests. If you are constantly throwing away cut and damaged power cords, you might give this more than a passing thought.
I don’t have to tell you that damaged power cords represent a much greater risk than a damaged mic cable or speaker cable. The liability aspect alone should make you vigilant in making sure your power cords, extension cords, plug strips and all things electrical are in perfect working order. Having someone injured or worse would buy a lot of power cords, if not the whole factory.
And, finally, we come to my favorite subject about power cords: length. In most rack installs, you have a plug strip right next to the device. You don’t need a six-foot power cord, you need a 3 ft., 2 ft. or even 1.5 ft. cord. So what do you do? Tie it up with a cable tie? Some installers (laboriously) cut down their 6 ft. cables and put on AC plugs at the length they need. A much easier way is to buy short power cords, such as those made by Volex (www.volex.com).
If you take any road trips outside the U.S., you can easily buy adaptors for each country. An adaptor might be fine for a laptop but it’s probably not a good idea for serious audio, video or broadcast gear. An adaptor adds yet another point of failure. And most adaptors are, shall we say, made to be cost-effective (i.e. cheap!). I shudder to think that a $250,000 mixing console is dependent on a $1.29 plastic adaptor.
The other end of a detachable power cord is most often the international standard IEC-320, rectangular hole with three flat pins, easily available everywhere. You might check your gear just to see what has removable cords and what doesn’t.
While you’re at it, what will run on 240 volts, as well as 120 volts, and what won’t? There was a great two-page spread titled “Plugged In” by Peter Gwinn in the June 2005 National Geographic Magazine on the world of power plugs. It showed most of the plugs around the world. The trick is, of course, to buy the correct cord for each box. Here’s a checklist:
- Gage size. Remember that, as you go up in voltage, you go down in current for the same wattage (VA), so you can often take smaller cords to Europe than American cords.
- Ruggedness. If the cord you’re replacing is extra-rugged, obviously its replacement better be just like it, or as close as you can get.
- Length. There’s nothing more frustrating than having the right plug, the right ruggedness and the right wire gage on a six-foot cord, only to realize the original cord was a ten-footer.
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