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Didital Things
Topic: Upsampling vs. oversampling

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Posted by Romy the Cat on 08-23-2010
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People argue out there if a DAC need to do upsampling.  I usually do not like the upsampling DAC and always prefer, or even insist to play in whatever format the source is.  Some DACs do not ask you and upsample the incoming stream to 2x  and higher if you ask it or not. Some of them let to defeat upsampling and some just make you to feel that you defeat something but in reality just inject a different type of dither.

What however everyone misses in the upsampling view is the fact that the upsampling result is very much differs from CD to CD. With some CDs the upsampling does not ruing sound and is absolutely not distinguishable with direct processing. And of course there are some CDs that sound juts horribly after upsampling. I do not know what on CDs made them to be upsampleable or not but as a practitioner I do feel a need to have 2 DACs of my main DAC is upsampling-type with not true defeatable upsampling. (most of the DACs nowadays). I do would like to learn what make CDs not upsampleable…
The Cat
Posted by manisandher on 08-25-2010
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I'm no expert, but my understanding is this. 99.9% of DACs are going to oversample the digital input anyway. Does it therefore matter if the input is upsampled or not? Unless there is a super-duper interpolation algorithm that can create more information from that which is encoded in the 1fs file, I don't see how upsampling can ever improve the sound, over and above what oversampling will do anyway. I've tried many upsampling schemes, and like you Romy, I've reverted back to playing all files at their native rates. Upsampling seems to kill the sound, though interestingly, oversampling doesn't (at least on the PM Model Two). Of course, this is very much dependent on the quality of the filters used.

FWIW, my feeling is that oversampling is absolutely necessary for rates below 4fs - I don't agree with NOS DACs for 1fs. At 4fs and above, I don't think oversampling is necessary and that NOS may work well here, though of course all delta-sigma DACs need to oversample at 128x or 256x in order to work anyway.

Mani.

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