pippin wrote: > So what you are saying is that if you use these kind of DACs with "real" > (that is: unfiltered) HD material like actual HD recordings you will > have all the aliasing down there in the audible band? > This means you have to actually run "real" HD material through a filter > to get a useful reproduction with this kind of DAC at all? > > Oh, and I did not fully understand what you mean with a "simple" vs. a > "complex" filter. Interpolation will certainly lead to rather complex > harmonics so from a purely signal theory POV I would find that way more > complex than what you'd usually do in an anti-aliasing filter.
Let me see if I understand your first question. As long as the highest frequency of the audio data is small relative to the sample rate (say 40KHz maximum signal frequency for a 192 sample rate) you do not need much if any filtering. There are going to be very little aliasing and its going to be above the audio range. The big problem comes with 44.1 where the audio data is right next to the aliases. By a complex filter I mean multiple filters cascaded together (especially different types of filters) rather than one filter (even if it has a large number of taps). All of the DAC chips with filters have at least three (some 4) different digital filters cascaded together. They do this because the individual filters can be a fairly small number of taps. To implement the same amount of alias suppression with a simple single filter would take a lot more hardware. Again I have no idea why the complex filters cause sonic issues, but it does seem like they do. Every time I have replaced a complex filter with a simple filter the resulting music sounds much better. John S. ------------------------------------------------------------------------ JohnSwenson's Profile: http://forums.slimdevices.com/member.php?userid=5974 View this thread: http://forums.slimdevices.com/showthread.php?t=99088 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
