President's Message
March 2003

1. The standard RCA connecting cable has two conductors: hot and ground (or shield). The nomenclature is misleading since just as much signal passes through the ground lead as the hot lead. This can be a problem if external radiation (60 Hz hum or radio frequencies) induces current in the shield which becomes part of the audio signal. This happens no matter how perfect the shield. A way around this is to have an overall shield which doesn't carry audio. Professionals use balanced cables for this reason, but the expense of interfacing with standard gear makes this option prohibitively expense for most consumers. A simpler solution is to use two insulated conductors with a separate shield and drain wire. This is almost unknown in the marketplace, but you can easily make your own. The drawback is that most multiconductor cables are relatively high capacitance and there can be some crosstalk between left and right channels. However with typical equipment outputs and cable lengths up to 25 feet this is not a problem. The overall shield can be handled in various ways: connect at both ends to ground (not advised since this brings you back to the original problem), leave both ends floating (probably not the best), ground at one end and float the other (most common method), ground one end and connect the other to ground through a .1 microfarad capacitor (I like this one--it provides an open circuit for hum frequencies, a short circuit to ground for RF), or connect both ends to ground through a .1 microfarad cap (probably not as good as the previous). A 20 foot cable made this way measured 850 pF. For comparison a cable made with Belden 9454 stereo cable would be about 250 pF. One could wrap aluminum foil around the Belden and spiral wrap buss wire around the foil to achieve both low capacitance and complete shielding.

2. A new device, announced at the Consumer Electronics Show in Las Vegas, allows ripping [webmaster's note: wouldn't that be shredding?] 30 CDs a minute. The name tells how this is accomplished. The MD100 Media Destroyer, from Royal Information Products, will be available this spring at major office supply stores for $130. It has a 5-inch slot on top for inserting diskettes or CDs. Special rollers inside the machine obliterate any data on the surface of the disc so that the shards will be unreadable. It also shreds 7 folded sheets of paper at once. NYT 23Ja03

3. For several years Stephen Webber, professor of music production and engineering, has been trying to introduce a course on turntablism at Berklee College of Music. It would teach the basics of manipulating a record back and forth against the needle to create percussive scratches, jagged beats and abstract sounds. But so far the college has turned him down. Meanwhile he has written a book "Turntable Technique" The Art of the DJ." He includes exercises like basic back-spinning and beat matching and advanced ones like the four-finger crab scratch. "It has become a musical instrument...Once I saw DJ Q-Bert and Mixmaster Mike who elevate this to a virtuosic level, I realized this could be around for a long time." NYT 11Fe03

David Hadaway

President, Boston Audio Society


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Boston MA 02126

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updated 11/11/04