[CLUE-Tech] Sound card/speaker "feedback" problem

[Grant Johnson]

I, however, am an audio engineer.  If it is a buzz or a hiss, it is 
noise. As opposed to a squeal that starts low, then the pitch rises to a 
squeal, and the distance from the speaker to the mic, which is a 
feedback loop.

Things you can do for noise:
1) Identify the noisy part, and turn down everything after it in the 
signal path.  For instance, you may get better results by turning down 
the knob on your speakers, and using the PC mixer to increase overall 
volume and individual sources.  Try each way around.  One will be better 
than the other.
2) Get better equipment.  Not much of a consolation, but sometimes, this 
is all you can do.  
3) Isolate, combine, or improve grounds.  If this hum is at 60 hz, you 
can ground isolate on the signal line, ground tie on the power side, or 
at least make sure you have good grounding on everything.  If one thing 
has more resistance to ground than the other, the ground will use the 
signal path as the route of least resistance, and cause sound problems.
4) Switch to a balanced setup.  If you go from the standard 2 conductor 
audio cables, to equipment designed fro, and using 3 conductors per 
channel, you can make longer runs without noise problems, because it 
uses distance from ground on 2 signals, and a differential amplifier to 
remove noise.  This should not be needed for runs under 10 to 20 feet, 
and would be VERY EXPENSIVE.

Bubba style diagnostics:
Plug a pair of headphones straight into the sound card.  Is the noise 
there?  If so, you are jammed.  Buy a sound card.  If not, hook the 
speakers to a walkman running from batteries (not an AC adapter, this 
could be ground related)  Is it there?  If yes, buy speakers.  If it is 
there neither way, but it is there when they are hooked together, it is 
probably a ground problem.  you can try to improve your grounds, and 
make sure they are on the same ground circut, but if one or both is a 2 
prong plug, go to Radio Shack, spend $11 and buy a "Ground Loop Isolator"

Joe 'Zonker' Brockmeier wrote:

>On Tue, 12 Feb 2002, Kevin Cullis wrote:
>
>>>If it's just a loud hissing/buzzing noise, that's just the speakers
>>>amplifying the signal noise. (Note, I'm not an audio engineer, so
>>>that's probably not the correct technical term.)
>>>
>>This is what it sounds like, a humming/hissing noise. I've turned down
>>the speaker sound and it helps, but I was wondering if there is
>>something else I should consider to help out.
>>
>
>There probably isn't much you can do. It might help to turn down the
>sound on the computer, but you're probably going to get the buzzing
>and hissing to some degree when you push the speakers close to
>maximum volume.
>
>Take care,
>
>Zonker
>--
>Joe 'Zonker' Brockmeier -=- jbrockmeier at earthlink.net
>http://www.DissociatedPress.net/
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>"Crime made its appearance during the dawning age of literacy. What
>this means is that, as soon as people started to write, they started
>writing laws; this is because writing enabled them to do something
>they hadn't been able to do before. Writing enabled them to define
>in exact, fixed terms the behaviors they wanted the state to regulate,
>punish, and suppress." -- Daniel Quinn
>
>_______________________________________________
>CLUE-Tech mailing list
>CLUE-Tech at clue.denver.co.us
>http://clue.denver.co.us/mailman/listinfo/clue-tech
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://cluedenver.org/pipermail/clue-tech/attachments/20020212/e78826aa/attachment.html