+1 @reubent , digital volume controls will sacrifice resolution to control volume. An analogue pre-amp solves this issue and will bring a wider, more dynamic sound too, however good pre-amps will reveal shortcomings of the source components too if not properly matched.
Resolution drop
Long ago, I was working with a dealer to learn if a certain component would work for me in a certain system. I was reading over some emails I have from then and the dealer wanting me to ask oppo if the resolution stayed the same when volume dropped from 100 in my bluray player. I wasn't aware that resolution dropped in any component. Does this effect have a name? What drops... bit rate, sampling frequency, clarity, intelligibility?
Resolution Definition pertaining to music
a. The progression of a dissonant tone or chord to a consonant tone or chord.
b. The tone or chord to which such a progression is made.