I noticed that the more performing your system and, namely, the preamp you use, the more you have to regularly check the volume setting during your listening session.
I noticed every time I changed the preamp in my system... I have a sort of personal hit parade of which's which the most responding to different music solicitudes among my preamps: the Marantz 7C was better than CAT SL 1, Mayer's was better than 7C, Le Solstice IS better than Mayer's, Silver Rock is better than Le Solstice... unfortunately Serge's masterpiece is only good for line.level, so I've to constantly swap to Le Solstice for phono and Garradzilla's glorious sounding joys.
On every of the above gears, I've to more and more times have to go to the preamp pot and set a different volume setting,,, every disc or disk, almost every track needs its very own setting... the overall trueness greatly improves, size and harmonic blossoming changes are more right when right;-)
Cannot explain in all my ignorance whythis happens...
Maybe the improved resolutions makes the volume setting more sensitive and as sure every disc is recorded at a different level, this difference is more or less apparent.