It was when I heard the difference between the Mac and the Innuos Zenith Mk3 and the differences between usb cables when I truly began to understand that a streamer was sending an analog representation of a digital wavestream and that all of the analog variables applied to digital streaming.
@ghasley I have always believed that differences in digital outputs must be because of something in the time domain.
Noise and frequency response are easily measured and these streamers tend to measure ruler flat and noise tends to be down something like 100dB below the main tone...so inaudible.
But time domain....that's where we get jitter from optical....we can of course measure jitter. The other thing in the time domain is the wave form. We see R2R resistor ladder DACs producing a much prettier sine wave than Delta Sigma DACs. We see DACs where their slower filter produces a nicer sine wave than their fast/sharp filter.
We see DACs being ranked based on THD & Noise...but THD and noise are so low already, who cares if SINAD is 120 or 95? Only Audio Science Review people care...and that's measuring an ANALOG output stage.
So a digital out on a streamer? These suckers measure incredible with THD, SNR, and Frequency Response. Which leads me to the belief that the real issue is in the time domain and very few people are paying attention to the time domain...and that is why your DAC and its inputs are so important.
When people say they like their streamers coaxial but not not USB, this is one example IMO. Some people like Zen Stream coaxial but not USB....maybe this has to do with the streamer, the DAC, or both.
I draw the same conclusions with speakers cables and crossover parts. Things can be smeared in the time domain. Well known technical reviewers like Brent Butterworth still like to measure speaker cables using frequency response...but are IMO using the wrong tool.