On 7/13/2012 9:46 AM, Pete Smith N4ZR wrote: > Interesting point on phono plugs. I wonder if it would be useful to use > one of the Caig Labs chemicals on those shells to enhance their contact > with the jack.
Better to buy and use proper connectors. Switchcraft makes EXCELLENT phono and 3.5 mm plugs, and the lower cost plugs and jacks made by Neutrik's Asian subsidiary are pretty good. I buy them from Full Compass, a very good audio distributor in Madison, WI. But there's another more fundamental issue than the plug itself -- 99.9% of the time, the shell of the phono JACK built into the equipment doesn't go to the shielding enclosure, but instead goes to the "common" on the circuit board and wanders around for a while before it finds the chassis. This serious engineering mistake is a major cause of RFI. In the pro audio world, it's called "The Pin One Problem." And because it's a passive network, it both sends and receive RF trash. Now, it IS possible to terminate the cable shield to a properly implemented "ground layer" on a PC board, but as Henry Ott has observed both in his EMC seminars and in his classic text on EMC, any signal traces that cross a break in that layer can render it useless, putting RF trash on those external cables. Another point -- improper shield termination can also introduce instability in the circuit, because current doesn't flow where the designer hoped it would flow. Henry Ott's text is required reading. 73, Jim K9YC _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
