Re: 96kHz, or 88.2 kHz for eventual CD audio

Mike Rivers <mrivers@xxxxxxxxxxx> writes:

On Oct 29, 7:22 pm, Randy Yates <ya...@xxxxxxxx> wrote:

Wrong. Very, very wrong.

No. Oversimplified, very oversimplified.

It's really stupid to obstinately argue about something you have no clue
about. It belies a wrong attitude, and that portends a failure to learn.

I tell you this because I've learned it the hard way myself. It's HARD
to learn difficult things. I have spent DECADES learning and applying
this material. As Ringo Star sung in his 70's hit, "It Don't Come Easy."

Delta sigma ADCs REALLY DO get M*F_s samples samples per second (where M
is the oversampling ratio and F_s is the "baseband" sample rate). There
is NOTHING false about the samples, and they're NOT all the same
sample. Obviously that would buy you nothing.

In that case, why not USE all those samples and just call it a higher
sample rate? There must be a difference between what you're describing
and simply having a higher sample rate.

Do some reading on the subject:

Not just yet, thanks. I'd like to hear your simplified explanation
first rather than just stating that I was wrong.

Well, the simplest explanation is that the front-end (low-resolution)
ADC in a delta-sigma data converter really does sample at M*F_s samples
per second. I guess the point you're missing is that this is a very
coarse sampler - usually only 1 bit.

The problem is that delta sigma data converters are not simple; it is
not a one- or two-paragraph topic.

I do have a simplified explanation of delta sigma _DACs_ here:

http://www.digitalsignallabs.com/presentation.pdf

Most of the same concepts apply to delta sigma ADCs as well - just
substitute a decimator for the interpolator and reverse the order of the
decimator and modulator. Additionally, part of the modulator must be
analog - see Figure 6-2 in

http://www.digitalsignallabs.com/SigmaDelta.pdf

which is also a nice tutorial on the subject by Sangil Park of Motorola.

Key things to take away are that a) the quantization noise of an ADC
does not change with the sample rate, and b) the ability of a simple
oversampling converter (without noise-shaping) followed by a lowpass
filter to extend the precision of the front-end ADC, and c) the concept
of noise-shaping to yield much better improvements in precision (see my
Figure 9).
--
% Randy Yates % "She's sweet on Wagner-I think she'd die for Beethoven.
%% Fuquay-Varina, NC % She love the way Puccini lays down a tune, and
%%% 919-577-9882 % Verdi's always creepin' from her room."
%%%% <yates@xxxxxxxx> % "Rockaria", *A New World Record*, ELO
http://www.digitalsignallabs.com
.

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