In my experience there is zero question that the most important thing determining sound quality - more than nearly any component, is the recording/mastering. They need not be new - some of the best "digital" are well mastered CDs from 1960s jazz recordings and orchestral by Verve, Blue Note, Mercury Living Presence (mighty Fine recordings).
Could your preamp be warming up? Maybe. Is it the big difference? Unlikely.
I have no heard the 3 you refer to, but may go listen to them.
Could your preamp be warming up? Maybe. Is it the big difference? Unlikely.
I have no heard the 3 you refer to, but may go listen to them.