-231a- Electricity, Lighting, Amps, Routers and Patch bays.


While seeking fresh ideas for this article, I visited veteran studio builder, Norman Rosenshein, president of Nortel Television Systems, Inc. in Elizabeth, NJ (908-289-0900). Here are some of the things he thought potential studio builders should consider:

Electric power (AC) -

If you live near an industrial park or in some cities, you may experience brownouts, surges, and electrical spikes. These raise havoc with sensitive electrical equipment such as time base correctors and sync generators. You may wish to provide regulated power to your control room equipment to insure that it gets the juice it needs. (I remember years ago when VCRs used to run a tad slow in New York City during their brownouts. The problem wouldn't become noticeable until the voltage came back to normal and none of the tapes would track correctly.)

One way to dampen spikes and surges is to install a power transformer on your studio electric line. The transformer will smooth out irregularities in the sine wave we call alternating current.

Lighting -

To save money on air conditioning and electricity, consider deviating from the Paleolithic practice of using incandescent studio lights. Videssence, Lowel, LighTech, and Belcar make fluorescent studio lighting fixtures that consume less than half the power of their incandescent counterparts for the same amount of usable light, are dimmable, and come in various color temperature ranges, which make it possible to mix these lights with conventional fixtures which are more focusable. Remember that a watt saved in lighting is saved twice: once in the lamp and once in the air conditioner.

Distribution amplifiers -

Most distribution amplifiers are differential amplifiers which means that they can reject hum (common mode interference) much like audio balanced lines do. A distribution amplifier is an obvious choice when you have to send one signal to several places, but here's a situation where a differential amplifier with one output is useful: You have video cables running from other buildings or areas outside of your shop. Video signals come in on these cables and you might patch these signals to routing switchers, processing amplifiers, VCRs, or various other gear. The problem is, most of these machines don't have differential inputs. As a result, any hum or interference that got into the line on the way to you, ends up in your picture. If you route the signal to your differential amplifier first, the hum is cleaned up and a pure signal is passed along to the next device.

I asked Mr. Rosenshein if it would be smarter to install the differential amplifier just before the patch bay so that the signal at the patch bay was always hum free. This would keep from accidentally patching the uncorrected signal directly to some device. His answer was no, don't do it. You should have the raw signal appear at the patch bay, normalled to the differential amplifier, and the amplifier's output would appear at the patch bay normalled to the next destination. The reason: if the distribution amplifier poops out (which they do), you can patch around it easily and save the day with a less-than-perfect but still visible picture.

Another little known use for distribution amplifiers: Say you are using a processing amplifier with two outputs and you are using both outputs. Did you know that in most cases if you switch the proc amp to "bypass" or turn off its power, the first output will loop the signal (not losing it); the second output dies. If both outputs are important to you, it is better to place a distribution amplifier after the primary proc amp output and send that signal to both places. Thus when the proc amp is switched to bypass, everybody still gets a signal.

Differential distribution amplifiers cost about $300 to $500 and are available from Datatech, Grass Valley, Sigma, Lenco, and others.

Routing switchers -

Routing switchers are needed in edit and duplication areas more than you'd think, and are too often omitted. Reasons: A VCR (or other device) has probably one video output. You can patch it to go wherever you want, but it is still only one output. With a routing switcher, you can press several buttons and send one signal to several places. If patching, your only choice would be to send the signal to a distribution amplifier and manually patch its outputs to several places. Mr. Rosenshein perfers a belt and suspenders by installing a distribution amplifier before the routing switcher; the DA sends one output to the routing switcher, another to the studio switcher, and a third to a monitor (you always need a monitor).

Most routing switchers have an audio-follow-video feature allowing the sound to switch along with the picture. The better models have a multilevel breakaway permitting you to switch just the picture, or just one or two channels of the sound individually. And speaking of sound, professionals who can afford it would probably buy four channel audio in their routing switchers. Industrial users can probably get by with just stereo.

Patch bays -

Buy the 3.5" patch bays; avoid the skinny ones. Why? Because you can't read the lables on the skinny ones without an electron microscope. The 3.5" patch bays leave plenty of space for legends.

Make sure your patch bay panel block (the part near the BNC connectors) is an insulator. You want the coaxial shields from the video cables to be completely isolated from all building metal. This way, when you patch a signal, the center wire connects all the way to its destination and the shield wire connects all the way to its destination, and nowhere else. If per chance the shield were to touch building metal or become grounded in some other way, it would "fool" the differential amplifier allowing hum and interference to infiltrate the line.

For audio patch bays the opposite is true. Balanced audio lines come into the jack bay as three wires, two signal carrying "hot" wires and a ground shield. The ground shields can all be tied together and grounded to the jack field and to what other ground straps you have. The wires leaving the jack field may go to distant places and the books say to lift (disconnect) the ground at the far ends. Thus the ground wire never gets to make a complete circuit which causes hum, ground loops, and other interference. Mr. Rosenshein feels, however, that it is no big deal if you leave the grounds connected. His answer is: If it works, fine. If it hums, plug in a ground lifter which will probably solve your problem. So what is a ground lifter? It is NOT one of those little adapters that allows you to plug a 3-prong (grounded) appliance into a 2-prong electrical socket (a move which may have shocking results). The audio ground lifter is a little adapter with a male XLR plug at one end and a female at the other. The two hot pins are connected straight through but the ground pins run to a switch that can be opened, breaking, or "lifting" the ground connection (adding no danger of electrical shock).

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