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[DPRG] Feedback prevention

Subject: [DPRG] Feedback prevention
From: Kipton Moravec kip at kdream.com
Date: Mon Oct 18 09:11:20 CDT 2004

I searched and did not find anything useful yet. Still looking

I did find a discussion from a company that makes such things.
http://www.sabine.com/RESOURCES/FBX/Literature/FBX-Best-Lit-LRZ-030120.pdf

It looks like they use notched filters at the point of the feedback 
frequency.  But that frequency is dependent on a bunch of things like mike, 
amp, speaker, room, position -- basically everything that can very from one 
time to the next, or as the person with the microphone moves.

Does not seem trivial.

Kip

At 07:03 AM 10/18/04, you wrote:
>I tried a google search on "microphone feedback prevention schematic" and it
>returned around 8760 hits for me.
>There has to be a circuit design you could use out of all of that someplace.
>It had a lot of techniques on reducing feedback problems too.
>
>-----Original Message-----
>From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org] On Behalf
>Of Dale Wheat
>Sent: Sunday, October 17, 2004 10:49 PM
>To: dprglist at dprg.org
>Subject: [DPRG] Feedback prevention
>
>Pres. John has tasked me with investigating possibilities for a
>club-owned PA system for our public events that need public addressing.
>
>One of the criteria was automatic feedback elimination.  This is a
>pricey add-on to any system, it turns out.  An outboard unit will cost
>between $300 and $500.  It is also available as a feature of powered
>mixers in the $600-$900 range.
>
>To me this seems like a lot of $$$ for something that surely someone
>amongst us can whip together with a DSP, duct tape & bailing wire.
>
>Any suggestions?  I'd be willing to do most of the
>building/coding/whatever if someone can point me in the right direction.
>   I have extensive microcontroller experience, but have only glanced at
>DSP stuff, and that a long time ago.
>
>Wouldn't a short delay (20-50ms) cancel out most feedback?
>
>Thanks,
>
>Dale Wheat
>http://dalewheat.com
>(972) 486-1317
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>
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