Upsampling for EQ

[ipeverywhere]

I’m hiding my uniformed response as a simple forum search (I should have done this) shows Roon explained this back in '17

Parametric EQ and DSD playback

We do indeed process DSD without performing a DSD->PCM conversion first. The signal path is reflecting that accurately. I’m going to explain how it works–keep in mind that there are some subtle technical details here, and some background knowledge is required to understand them fully. Processing DSD isn’t nearly as straightforward as processing PCM. With the exception of a few simple operations, you can’t process it directly in the 1-bit representation. There are more steps involved, but it’s p…

Summary

I’m going to throw a guess here…
EQ only works on PCM. What you’re not seeing in the first path is a conversion from DSD -> PCM -> EQ -> new PCM -> DSD. I have no idea if there would be any benefit to converting upsampled DSD128 to PCM and then back again. When keeping DSD as the output format then it coverts the “native” DSD to PCM to hand to EQ which then hands it back to the DSD engine for upsampling. Again, this is a bit of a guess.

When you output PCM then DSD is converted to PCM first and the hidden path is 384k PCM -> EQ -> new PCM. So there is not conversion back to DSD out of the EQ filters.