1. News headline: "GM Will Increase XLR Output." Actually, General Motors is not getting into audio connector manufacturing,
but rather the Cadillac XLR roadster.
2. "Cable Makes a Difference." I recently installed a 21" CRT computer monitor and noticed "ghosts",
on text, i.e. a gray area to the right of each vertical black line. I have 15' of cable going to the monitor from the computer which is behind a closed
door. I had cascaded two cables to get the length. Joel Cohen suggested that the connectors are not truly 75 ohms and reflections can occur. I replaced
the two with a single 25' cable and the effect was much worse! Then he loaned me a 10' cable to cascade with the 6' one that came with the monitor and
the problem disappeared. The 10' cable was larger in diameter than the cables I was using. He said that the 5 conductors in his cable were individually
shielded miniature 75 ohm coax instead of loose wire with overall shield and no characteristic impedance.
3. "Cable Doesn't Make a Difference." I was needing to make some long cables for audio with my computer, a secondary
application. I didn't want to use expensive cable so I looked in the MCM Electronics catalog. They list only one bulk stereo cable, #24-2580, 100' for
$9. I had ordered their budget cables and measured a high 100 pF/foot, so I was wary. Sure enough, the bulk cable was 100 pF/foot. Still, if the length
is less than 20' and the output impedance of the source is less than 1000 ohms (a good bet since it is also a headphone output) it is acceptable. A
plus is that the cable is flexible and small enough to fit in miniplugs. For regular RCA's I like to add a layer of shrink tubing before clamping the
strain relief.
David Hadaway
President, Boston Audio Society
email:
dhad000@yahoo.com
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