I’ve been using my FiiO X3ii and Schiit Vali 2 for 3-4 years now. Originally I was only playing mp4a’s and mp3’s from my player. Recently I started reloading certain favorite CDs onto my computer as FLAC files at 44.1kHz 16 bit. Also recently I’ve started downloading some choice albums from HD Tracks, particularly last night with their 20-45% off sale. Couple of the Stones albums I got last night - Sticky Fingers and Let It Bleed, sound almost at the edge of distortion thru my setup with my HD6XX’s. The mix seems kind of “hot” compared to the same albums I loaded from CDs. Also I noticed the only sound quality option for these files was 44.1kHz 24 bit. I’ve downloaded 192kHz 24 bit files and never experienced this. Is 44.1kHz 24 bit an odd bitrate? Am I just hearing distortion from when they recorded these albums in 69/71? Do higher resolution tracks impact the tube in the Vali differently?
44.1 / 24 bit is very common. Just speaking from experience, a higher bit and sample rate will generally somewhat smooth over those rough edges you're hearing. I listen to primarily rock and metal, so that little bit of distortion can be a bit more pleasing. It mostly depends on the original recording, and how it was engineered and produced. Again, this has been my experience.
Most of the time it is 16 bit / 44.1 kHz.
24 bit / 44.1 is rare.
As 0 dBFS is the max in a DAC, 16 bit goes down to -96 dBFS and 24 to -144 dBFS.
So 24 bits can play those tiny detail below -96, it won’t play louder.
De most likely explanation is that you downloaded a remastered version.
These are in general louder than the original (the loudness war) and might by so hot you get digital clipping.
You might try a spectrum analyzer like https://www.sonicvisualiser.org/ to compare CD and download.