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In Reply to: Re: DAC ... its getting on my nerve posted by Presto on April 3, 2007 at 09:47:27:
Oversampling is required as a means of implementing a digital filter in order to bandlimit the signal to the Nyquist frequency to prevent aliasing. The Nyquist frequency is solely a result of the original sample rate. Oversampling does, as a consequence, push the D/A conversion artifacts (sample glitches) to a higher frequency which allows the use of a more gentle filter on the DAC output (analog domain) for their removal.Upsampling does change the Nyquist frequency to a degree, or at least spreads the spectrum and allows an anti-alias filter with a more gentle slope. Or something to that effect :-)
Follow Ups:
Slider:Okay - if oversampling does not do it...
So what if you upsample first before you get to your DAC. Is not the Nyquist frequency pushed up in THAT case?
I thought if you upsampled your original sample rate now *is* the new sample rate...
Just wondering.
Cheers,
Presto
Upsampling is kind of like resampling the signal at a higher rate, as you say in your message. If it could be done with a high enough precision, it would seem to be almost a "free" process to increase the sample rate and avoid the problems that result from extremely steep filtering at the Nyquist frequency. Unfortunately, it seems to just add a new set of problems, along with the additional filter stage. Guess nothing comes for free in the real world. But the tradeoffs may result in something better.
Slider:I guess that's why some like upsampling and others don't!!
Thanks for chiming in...
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