Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!jarthur!rspangle
From: rspangle@jarthur.Claremont.EDU (Randy Spangler)
Newsgroups: sci.electronics
Subject: PC speaker to stereo (update)
Message-ID: <6062@jarthur.Claremont.EDU>
Date: 10 Apr 90 23:40:00 GMT
Distribution: na
Organization: Harvey Mudd College, Claremont, CA 91711
Lines: 30

Well, Heath Roberts suggested I have the leads that were going to my
stereo go to one side of an audio transformer, and then take the other
side and attach that to my stereo. 

Result: massive improvement in sound quality

Problem: I still get a high whine (mostly >2KHz) even when the speaker isn't
doing anything.  I figured it was probably RF interference from the monitor
cable, since the whine changed timbre (sound, but not pitch) when my 
display changed (when a directory listing popped up or whatever).  So I 
wrapped (separately) my entire circuit and the entire monitor cable in 
aluminum foil and grounded them to the chassis.  

But the whine remained.  In fact, it remained even when I unplugged the 
monitor cable from the computer and turned off the monitor!  The whine also
still changed sound when I updated the display.  So I figure it's the card
which is putting out nasty RF somewhere inside the computer.

How do I fix this?  I'm a little nervous about waving aluminum foil near my
computer's chips (crack!  Oh, good, the noise went away.  Oh.  Oh.  Oh.)
Would wrapping the cord around an RF choke help?

(BTW, the card is a Paradise Pro 16-bit SVGA)


-- 
 --------------------------------------------------------------------------
|    Randy Spangler                    |    The less things change, the    |
|    rspangle@jarthur.claremont.edu    |    more they remain the same      |
 --------------------------------------------------------------------------