All DACs are different
in one fundamental quality , they all have a slightly or grossly different output levels. I have 3 CD players and several external DACs, no two have the same output level. I have recorded samples from different combos and easiy DBT'd the differences, however when I volume adjust the samples to be approximately the same I fail such tests. We, most of the time perceive slightly louder as better. Thus non level matched comparisons are a bit misleading.
some DACs are really different
some manufacturers like Wadia have tweaks such as aggressive low pass filters that deliberately drop the higher frequencies by up to -3db at 20khz, for younger listeners this is possibly audible in itself. Some CD player/DACs with tube stages can have very uneven FR such as the AH Njoe Tube designs. Some designs are so incompetent (such as the Zanden 5000 which is not even nominally flat till it hits 200hz) that it's massive flaws are perceived as "character". It is trivial to make a DAC sound different if you really want to.
most DACs are however pretty similar
The vast majority of DACs however do a splendidly competent job at recreating an analog waveform with low distortion, low noise, low phase differences, low channel imbalances, flat frequency response, low sample timing variations and so on. In a word accurate. Excluding output levels two competent DACs will be so exemplary on measurable criteria that audibly telling them apart by such criteria will be extraordinarily difficult if not impossible. For instance an SNR of 108db is twice as good as an SNR of 102db but outside of an anechoic chamber with ear-bleeding levels you'd not tell them apart.
at this point
someone usually says but you cannot measure X or Y. Normally something like PRAT or Timbre. Well PRAT is so badly defined and so subjectively perceived that is it not terribly useful. Pace would seem to imply speed or timing variations easily measurable. Rythmn - surely nothing can change the meter of the music, Timing again implies timing variations. Timbre is all about Frequencies, harmonics, phase differences and so on, again measurable phenomenon.