[pd-ot] electric circuits in software

Christian Klippel ck at mamalala.de
Thu Apr 27 07:55:50 CEST 2006


hi,

Am Donnerstag, 27. April 2006 05:39 schrieb Chris McCormick:
> On Wed, Apr 26, 2006 at 11:30:34PM -0400, Mathieu Bouchard wrote:
> > On Wed, 26 Apr 2006, Hans-Christoph Steiner wrote:
> > > but then there are many audiophiles that say things like "double-blind
> > > tests hide the differences in equipment".
> >
> > So, basically, they are acknowledging that the differences in equipment
> > are due to prejudice, branding, advertisements, colour of the case,
> > gadgetism, and corporate/academic equipment procuration policies ;-)
>
> Heheh. One thing I've always wondered about (and I could be about to
> highlight my total lack of signal progressing understanding) is the
> representation of two waveforms at Nyquist; if you have a squarewave
> and a sawtooth wave, both sampled at 44100 and playing at a frequency
> of 22050, these waves will both be represented by two samples each,
> correct? So when they are sent back into the analogue domain, won't these

yes. but in analog audio adc's, you usually have an digital and/or an analogue 
antialiasing filter. also, frequencies close to nyquist are always 
problematic to reconstruct, due to the nature of the sampling.

often, the output is modulated when you have frequencies very close to sr/2.

> two waveforms look identical? Wouldn't they look like exactly the same
> sound? On analogue gear, wouldn't it be the case that the exact shape
> of the waveforms would be more accurately represented (e.g. a sawtooth
> and a squarewave at 22050 would look like such)?

on analogue gear you have no samplerate at all. its continous.

when played as digital source, a waveform at sr/2 will always look sine-like, 
regardles of the osc source beeing a sine or rectangle osc. (at least on my 
scope ....)

depending on the used dac (=quality, circuitry), even a 10 khz wave looks more 
sine like, even if the source is meant to be a rectangle....

>
> Best,
>
> Chris.
>

greets,

chris

> -------------------
> chris at mccormick.cx
> http://mccormick.cx
>
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