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From: fc@lexicon.com (Frank Cunningham)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: audio digitiser
Message-ID: <577@lexicon.com>
Date: 16 Mar 90 18:57:44 GMT
References: <8649@chaph.usc.edu>
Organization: Lexicon, Inc., Waltham, MA
Lines: 22
In-reply-to: wdao@castor.usc.edu's message of 16 Mar 90 06:13:25 GMT

In article <8649@chaph.usc.edu> wdao@castor.usc.edu (Walter Dao) writes:
> In this month issue of Popular Electroniss (april 1990) there is a little 
> circuit that you can build that will improve the quality of digitised sounds.
> It is supposed to do some extra filtering and do some fiddling with the sound
> and make it more process-able by the available sound digitisers.
> ....
> ohhh , by the way, the gyzmo's name is called the "ditherizer".
						    ^^^^^^^^^^^^^

Dithering is often used in professional audio systems to improve the
low level performance of A-D convertors and DSP stages. To dither a
signal, one adds noise to it at a level of around the LSB, ahead of
the A-D convertor, thus randomizing the conversion. The randomized
conversion has uncorrelated noise added instead of the correlated and
usually inharmonic stuff that results from converting music to square
waves (which is what you get if the low level parts of the signal
wiggle only the LSB).
-- 
-Frank Cunningham   smart: fc@lexicon.com	phone: (617) 891-6790
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