Cause of different sound between dacs

That's too simple.

Look inside. No two are exactly the same. They are all different. Only question is how similar or different any two are.

If you ever try two brands of vanilla ice cream, that taste EXACTLY the same, they probably are, ie same stuff under a different label. That happens on occasion with audio gear (exact same product marketed under two different brands) but not often.

Look inside. No two are exactly the same. They are all different. Only question is how similar or different any two are.

If you ever try two brands of vanilla ice cream, that taste EXACTLY the same, they probably are, ie same stuff under a different label. That happens on occasion with audio gear (exact same product marketed under two different brands) but not often.

It's easy to establish via careful listening that two DACs sound different just by a/b testing. Like vanilla and french vanilla say. But a lot harder to establish which is in fact BETTER. Which is better, Vanilla or Chocolate? Two things that are different cannot be equally good. One may beat another in one aspect of sound and lose in another. Differences might be subtle. Some may not matter to any particular individual, others may. What is better is often determined by personal preferences in choosing between two different beasts.