You're confusing "different" with "better".
If you compare 2 products that measure well (thereby indicating that there should be no audible differences), the only way to establish an objectively verifiable difference in sound is through double-blind testing. Without this, it is impossible to isolate the cause of the perceived difference. In other words, any differences in sound are far more likely to originate in cognitive bias rather than in the audio equipment used.
I agree. Which is why I put "better" in quotes since it is subjective. It's like the amount of salt you want in your food or the amount of sugar, you like in your tea.
On the flip side, there have been ABX tests with devices that measure pretty much the same (where there should be no audible difference) that have shown that an "educated" listener (by "educated" I mean some familiar with both the products being tested) is able to distinguish with a degree of regularity that is more than random. I am not referring to any snake oil stuff (I do not subscribe to the Peter Belt mindset).
In the "old days" have been part of a few such tests myself. The DIYer/Cheapskate in me always hopes the less expensive product wins a test (besides who doesn't like a David vs Goliath story) but even given this bias I have had to concede that in many cases while the price of the more expensive amplifier may not be justifiable, it did have more authority; or that the more expensive CD player (this was the day when Wolfson, BurrBrown, TI and Cirrus Logic DACs were considered to be the ones to compare) was more "musical"/ "organic" or less "digital".
Audio is both, objective because we like to be able to measure what we are hearing; and subjective because we all have our preferences (sometimes these may be subconscious).
When it comes to DACs, most people will say it is the implementation that matters most. At the same time, we hear whispers and opinions of AKM-chip based DACs being smoother (in general), and ESS-chip based DACs having a hotter, more extended high end. Without even getting into other DAC topologies, even chip-based DACs are "said" to sound more different, than their measurements would suggest.
Unfortunately, I now live in a country where access to outboard DACs is almost non-existant. We don't have any "high end" audio market. Otherwise, I would happily subject myself to ABX tests and report my experiences.
Which is why I am on this forum. I hope to live vicariously and learn from you guys!
"
You can take the boy from audio, but you cant take the audio from the boy"