It would be illustrative if someone or some outfit like the venerated or hated depending on your views, like ASR, could take a streamer, feed it a known series of data and then simply measure the digital output to see how accurate that output really is.
Obviously, things like jitter, if the measuring equipment is good enough to discern it, can play a part too in how we perceive the quality of that output. But do you REALLY want to know the truth, or would you rather be happy in simply accepting that you think one streamer sounds better than another feeding the same external DAC via the same digital input?
Like the old Star Trek episode goes, "Is there in truth, no beauty?" or as John Keats put it, "truth is beauty, and beauty is truth". But you might prefer your beautiful girlfriend with a little makeup on.
Are streamers digitally enhanced?
I had a conversation yesterday with a studio engineer friend and I was telling him about the sound of my Innuos Pulse. He has heard my system with the Node 2i and was skeptical about how much difference a better streamer could make.
After I described improvements in soundstage and overall sound quality he remarked that it sounded like some digital enhancement, similar to a studio plugin, was part of the higher end circuitry. I offered that it was revealing, not enhancing, and he replied "how do you know".
How do we know? Digital circuitry is controlled by software/algorithms and these can't be readily seen like hardware. When new hardware comes out, reviewers can open the hood and look inside. But what do we know about how streamers or DACs are processing the signal? Is the goal purity or beauty?