In Reply to: Not quite right. posted by Ted Smith on February 13, 2007 at 12:50:30:
Ted,
you are absolutely right about Nyquists theorem. Of course when it says 'bandlimited waveforms' this actually means that it is not possible to reproduce a square wave of any frequency as square waves contain all harmonics at equal level. Personally I like my kit to be able to reproduce any waveform successfully, at least within the range of human hearing.
And I don't know about you or anybody else but I can quite easily hear the difference between sine, sawtooth and square wave up to at least 16kHz (thats were my generator cuts out).
It is also true that I have not read the "real book on sampling theory"; my sources here are a lecturer at a technical college (his subject: Digital Audio) and my uncle (Phd in higher mathematics and >10 years of R&D for the European Space Agency specialising in all things digital ie digital data transmission, fractals etc).Either way I can't really see how it would be possible to recreate a sine accurately if during the recording process the actual peak values are missed. You can't recreate what has never been encoded. By the way last time I looked the 'reconstruction filter' was nothing more then a slew generator which leads to a phase delay which tends towards 90deg as the 'two samples per cycle' situation is approached. Feel free to elucidate...
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Follow Ups
- Re: Not quite right. - b.l.zeebub 02:07:27 02/14/07 (11)
- it IS a little confusing - tunenut 15:01:06 02/15/07 (1)
- Re: Not quite right. - andy19191 03:13:20 02/14/07 (9)
- Re: Not quite right. - b.l.zeebub 10:53:10 02/14/07 (8)
- Here's a picture - Ted Smith 14:42:32 02/14/07 (0)
- Re: Not quite right. - andy19191 11:54:06 02/14/07 (0)
- Re: Not quite right. - Ted Smith 11:17:27 02/14/07 (5)
- Re: Not quite right. - Werner 04:21:29 02/15/07 (4)
- Thanks - Ted Smith 09:13:49 02/15/07 (3)
- Re: Thanks - Werner 23:19:14 02/15/07 (2)
- Re: Thanks - Ted Smith 00:30:07 02/16/07 (1)
- Re: Thanks - graemme 00:46:18 02/21/07 (0)