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Subject: Re: Is it Possible?
NNTP-Posting-Date: Mon, 13 Jan 2003 08:12:25 GMT
Organization: AT&T Broadband
Date: Mon, 13 Jan 2003 08:12:25 GMT
Ken McDonald wrote:
> I want to build a circuit to eliminate the center channel from a
> stereo input. I think I can do it by inverting one channel and sum
> it with the other channel.
Bravo. That's the right idea. Keep going.
> Or feed both inputs into a differential amplifier. The only
> problem is I end up with a mono output.
Uh-oh, let your idea simmer and stew just a little longer. I think it
is only yet half cooked.
> What I really want is to eliminate the center channel and still have
> a separate left and right channel. Is it possible?
Of course! Just think symmetrically and prepare both channels with the
same design recipe. For example, to decimate a center mixed vocal while
maintaining the rest of the stereo information try the following from
the Karaoke Cookbook(tm).
First use a pair of opamps to individually invert the left and right
vocal portion of *both* channels. While you're at it, trim well all
excess non vocal fat from both signals by band limiting them
appropriately to taste (say, 200 to 2kHz). Now fold over and mix an
equal portion of each processed signal into its unprocessed stereo
counterpart. Serve up the cooked left and right signals via a second
set of opamp summers. Left "cooked" should equal left "raw" minus the
inverted vocals from the right channel, and right "cooked" should equal
right "raw" minus the inverted vocals from the left channel.
Bon Appétit! -- analog
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