Dude. The tiniest offset in "about same volume" makes you EXACTLY imagine "tone, texture, soft/not solid" kind of things. why do you think that carefully normalising volume (as
@amirm has done for several DACs already) makes these differences instantly disappear??
You are operating from a
total broscience kind of approach where you hear
exactly the kind of thing you want to hear. The kind of proper testing is hardly a kept secret and I'm honestly surprised at your careless approach to this. Blind test or not, if you aren't properly matching things will doubtlessly sound just that little bit different enough that you'd hear differences!!
Of course you are free to conduct tests as you please but I'm surely not alone in taking this kind of "obvious to you" experience with a great grain of salt (no offense)