John, thanks for trying to explain, but I'm still confused. Your very first paragraph is completely at odds with what I have always understood to be the purpose of oversampling in a DAC:
JohnSwenson wrote: > A 44.1 stream still needs to get filtered with a sharp cutoff filter > close to 20KHz in order to properly supress aliases. This is because we > know that there is going to be real input data all the way up to 20KHz. > A filter for 176.4 can get away with a less steep filter because we > assume that there will be no (or VERY little) actual data close to > 88KHz. If you take that 44.1 stream and zero stuff it and feed it into a > 176.4 filter with a shallow filter function it's not not going to get > properly filtered. I thought that the effect of oversampling (ie. zero-stuffing) was that it moves the aliasing artefacts up the frequency spectrum. If you 4x oversample a 44.1kHz signal, then the aliasing artefacts will begin at 88.2kHz instead of 22.05kHz. Hence you can use a much gentler reconstruction filter - indeed, you can in this case use EXACTLY the same filter that you would use on a non-oversampled 176.4kHz signal. Are you saying that I've been misunderstanding the purpose of playback oversampling all this time, and that when you oversample the aliasing artefacts are NOT moved up the frequency spectrum? If that is the case, then what IS the purpose of oversampling? ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=94352 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
