This is switching the burden of proof. There is a lot of evidence that people can't tell the difference between amps, DACs, sample rates,and wires of all sorts when they don't know what is playing (see "
Catalogue of Blind Tests"). There is ZERO evidence of that quality that they can. There is also a lot of audiological science suggesting that the differences among well-measuring equipment measure below the sensitivity of human hearing. The properly formed
Null Hypothesis, even before all that evidence, should be that there is
no audible difference. Those claiming DACs make a difference should produce a blind, level-matched, controlled ABX test demonstrating it. The burden of proof is on those asserting the Alternative Hypothesis (you), not those saying the Null Hypothesis has not been rejected (most of us here at ASR). And it is VERY telling that the makers of kilobuck DACs have never come up with such a test. Not once. Think about it.
Given the balance of the evidence to-date, it is
overwhelmingly likely that the changes you hear do not arise from the equipment, but elsewhere - level differences, room differences, and/or changes in your own mood or physiology.