In Reply to: Re: The Importance of Audio Measurements posted by jj on November 20, 2002 at 20:45:51:
Setup a PA system for touring the magnet division factory last summer. Found that balanced mike runs, when they hit the floor, produced exact replica's of the cable to floor impact through the speakers. Not noise, but perfect microphonics. With the mikes off. And every cord I tried. Six in all.I do suspect, however, that it was a combination of the plus to minus wires in the cable bouncing w/r to each other, and the stray magnetic fields present in the concrete rebar, on the order of tens of gauss.
The braid shielding of course, doesn't stop the external magnetic field from penetrating to the conductors.50 ohm cables are microphonic also. Take a scope, plug in a cable, and hit the cable end on the floor. There will be an interesting waveform on the scope.
TTFN, John
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- cable microphonics - John Escallier 10:38:05 11/21/02 (0)