I experimented lastly a lot with audio player software (Audirvana/Roon/Volumio/HQplayer) and different configurations including Raspberry Pi, Uptone Regen and USB cables.
The point was that I heard differences, but only small ones and when I finally went back to the simplest setup Macbook - USB cable - anTidac, honestly I missed nothing compared to the more complicated setups!
I also tried upsampling with HQlayer several times but in the long run it made the sound not better, perhaps because my computer os too old and slow for advanced signal processing.
Then I saw in a German forum an offer for an used USB cable made by a forum member who manufactures cables in a semi-commercial way and sells them mainly to friends and in the forum. It had a nice blue-metallic braid hose and cost only 50 €, so I thought, why not try an ambitious USB cable, even it's only for the good feeling. I didn't expect anything ele than marginal changes in sound but, my god, was I wrong!
Here is what I heard and wrote to the seller after the first listening:
"The sound of the cable troubles me currently very much!
I do not really believe in USB cable sound and just thought that having a good USB cable for a manageable amount would not hurt.
But it sounds subjectively different than my other USB cables. Bigger stage, with better depth layeringring and better dynamics. I've heard subtleties that I have not yet noticed. Actually, exactly what I yet have missed a bit in digital.
Strangely enough, the cable adds a somehow "dark" connotation, which I can not quite describe or classify which gave me after prolonged listening a slight ear pressure which was not the case otherwise.
I'm curious if that still changes with prolonged use or if it was possibly an autosuggestion."
I was lucky enough and the sideeffects of the "dark connotation" were not longer noticeable the next day and I could again not really believe what I heard. All sort of drums from bass drum to tom-toms had an enormous, almost frightening but totally effortless impact, same with the bass which had content down to never heard subsonic regions which means that the perceived dynamic has increased.
Everything is more pronounced layered in the depth and also the height of the virtual stage has increased, singers have a more realisitc height.
But also filigrane and quiet music like track 18. "Castor et Pollux, Acte I, Scene III: Prelude - Air accompagne 'Tristes apprets'" from the Rameaau recording by Teodor Currentzis sounded more intense and spatially better defined. The strings and voice act here often at the subtle threshold of tone creation which is presented very exquisitely.
And when powerful and quiet things are happening at the same time, they are now much more distinct and present. At the same time everything is connected in a musical way and the flow is much more natural.
Of course this makes me happy - and disturbs me a lot because I don't have any reasonable explanation for that!