Re: [LAU] Audio over WIFI

On Saturday 17 January 2015 22:12:20 Ralf Mardorf did opine And Gene did reply: Any of them unless they are built with matching but reversed biased from side to side stationary plates. The capacitance between 2 objects has a square-law relationship when the distance is varied. Since its a difficult problem trying to drive the central plate, the diaphragm, the movable by air pressure plate when its in close proximity to a stationary plate on both sides, they are are built only with a stationary back plate. As long as the spacing variation is a small fraction of the overall spacing, its not too bad, and has even been compensated for by using a FET preamp with the correct bias etc to introduce a compensating 2nd harmonic of the opposite polarity. The electret condenser type has a huge advantage in this case because they contain their own permanent charge, and its a quite high voltage, so the spacing can get sloppily large (= cheap to make) and still have adequate output to drive the FET buffer in it at quite low distortion. Radio Shack used to sell, for a tenner, a pencil mike that ran the FET on a pair of AAA cells, and it was pretty darned good for a 10 dollar mic. Way the heck and gone better than the $60 Shure clones they had at the same time. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS