@ecolnago
All digital cables affect sound of the DAC differently. In order to make sure DAC receives just right amount of data it has to synchronize internal D/A conversion rate with incoming data (S/Pidif) or receives data at different rate, but signals back to increase or reduce amount of incoming data (async USB, Ethernet). In case of async USB or Ethernet D/A conversion clock is independent of incoming data timing, but it might be affected indirectly by noise injected by the cable into DAC. S/Pdif delivers data in real time and the average rate of this data adjusts rate of D/A conversion. S/Pdif cable can affect this rate two ways. Coax S/Pdif cable transitions are fast, hence susceptible to electrical reflections in the cable, that add to and modify shape of transitions affecting timing. DAC corrects most of it by adjusting to average of the frequency, but it is not perfect. In addition cable injects picked up electrical noise. Optical cable is different. It doesn't inject electrical noise and doesn't create ground loops (like coax cable can), but transitions are very slow. Slow transitions in presence of electrical noise can affect exact moment in time of level recognition (crossing threshold). It all comes to making clock of internal D/A conversion stable in time. Jittery conversion clock produces noise added to music.
In case of Ethernet or USB I would pay attention only to quality of shielding and run cable away from other cables. Same goes for coax S/Pdif, but matching characteristic impedance of the cable (to avoid reflections) is also very important. It is also desired to keep cable very short - less than foot (to avoid reflections) or longer than 1.5m (to avoid first reflection). With optical cable, quality of the cable (clarity, etc) plays role, but the most important is to keep system electrical noise low, by using power conditioners for the source of the signal and the DAC.