What does DSD upsampling do?

Hi I never understood this, maybe someone can enlighten me. I hear that DSD upsampling is the fashionable thing these days, especially with Roon etc.

But what I don’t understand is: if your original recording is let’s say 16/44 or DSD128, how does upsampling to DSD512 help? There’s not any more information in the stream. How does it help sonic quality? Thanks.

The filters needed to decode 44.1/16, if not extremely well designed, can cause audible problems, such as phase shifts, as they need to be very sharp to remove ALL frequencies below 22.05kHz (44.1kHz / 2). By oversampling, you push that frequency much higher, eliminating the need for the deleterious sharp “brick” filters, and also allowing for easier to design, and less costly filters. If they pick a frequency of 56.448MHz, all sampling frequencies currently in use could be accommodated by one filter. You can not get MORE sound, but, in theory, you can get better sound

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I’ve experimented with upsampling from Roon and on some recordings it adds depth (but commonly at the expense of width and height). For most recordings the DSS does a better job with an “unmolested” feed

Both converting PCM to DSD and upsampling of DSD did not work for me. Things become dry and inorganic. However, upsampling PCM to 24/176 or 24/192 improved imaging, vocals, and instrumental presentation.

Even in hardware, it’s not clear cut. Although they offer it, Holo Audio on their May KTE dac recommends not to use oversampling. Denafrips recommends using oversampling for their Terminator Plus dac. Different strokes for different folks.

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