Re: [ARSCLIST] Sampling Theory (was Fred Layn's post on the Studer list re: Quantegy)

["Richard L. Hess" <ArcLists@xxxxxxxxxxxxxxx>]

Hello, Steven,

Ken Pohlmann's book on digital audio is a good reference. The
reconstruction filter on the output is similar to the anti-aliasing filter
on the input. In both instances, they are sharp cutoff slightly below half
the sampling frequency.

Charles Poynton's books are also good -- although they deal mostly with
digital video, the concept is the same. There may be some stuff on his Web
site http://www.poynton.com/

Cheers,

Richard

At 07:03 PM 1/15/2005 -0500, you wrote:
> ----- Original Message -----
> From: "Richard L. Hess" <ArcLists@xxxxxxxxxxxxxxx>
> > At 09:35 PM 1/13/2005 -0500, Steven C. Barr wrote:
> > >There is a difference, easily demonstrable by an a/b comparison
> > >using a pair of oscilliscopes. By definition, a digital waveform
> > >is a series of finite steps, not a smooth curve. Just as in integral
> > >calculus, the goal is to obtain an infinitely large set of
> > >infinitely small variations. However, the experts tell us that
> > >beyond a certain point the human ear and human mind cannot notice
> > >an identifiable difference.
> >
> > Steven,
> >
> > If you can see the steps on an oscilloscope on the analog output of a
> > properly designed digital to analog converter, it isn't properly designed.
> > The "reconstruction filter" on the output is defined and will not show the
> > steps. This is brother Nyquist.
> >
> > This is debated ad nauseam on the Pro-Audio list, and I'm not trying to
> > bring that discussion here, but you shouldn't be able to see the
> difference
> > on an oscilloscope or hear the difference.
> > Cheers,
> > Richard
> So...the d/a converter actually creates a smooth waveform rather than a set
> of steps. Is this done by averaging the values of adjacent "steps" somehow?
>
> I had no idea this was done...would the unfiltered signal sound essentially
> the same, or could we hear a distinct difference?
>
> Steven C. Barr