[BC] CD vs LP

[RichardBJohnson at comcast.net]

Dithering in a digital information system allows one to use
portions of bits, effectively pulse-width modulating the
bits. This improves the resolution which can improve
just about everything at low levels.

Suppose you had a signal that was so small that
only one bit was being exercised. It is either ON
or OFF. Basically, the harmonic distortion would
be that of a square wave, about 33 percent. Now,
if you dither the signal or the sample clock with
a noise signal with frequency components outside
the region of interest so the high-frequency junk
you are adding can be filtered out, the result, when
low-pass filtered will add signal information in
between the individual bit levels, effectively adding
resolution.

Of course, this only works with time-varying signals.
However, information is conveyed in time-varying
signals anyway, so in the "real world" we can obtain
real improvements in resolution, significantly reducing
low-level distortion, for instance. 

--
Cheers,
Richard B. Johnson
Read about my book
http://www.LymanSchool.org


 -------------- Original message ----------------------
From: Fred Gleason <fredg at paravelsystems.com>
> On Tuesday 23 September 2008 04:33:09 am RichardBJohnson at comcast.net wrote:
> > Dithering improves RESOLUTION, never DYNAMIC RANGE
> 
> Interesting Richard.  I always thought dithering was a technique for reducing 
> perceived noise and distortion, especially when transcoding between different 
> sample rates or sizes.  See, for example:
> 
>  	http://en.wikipedia.org/wiki/Dithering
> 
> I'd be interested to hear how this works with resolution as well.
> 
> Cheers!
> 
> 
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