Cause of different sound between dacs

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.

Two DACs can sound identical just because you are using a poor quality preamp or any active preamp at all in the system. These can totally homogenize all sources.

I don't use any preamp, active or passive. Makes a world of difference.

If you must use one, use a passive transformer. Requires the DAC to have decent output drive though...

Steve N.
Empirical Audio

Power supply is a huge factor. Also the output caps used are very, very important.

Great active tube preamp is the best option IMHO with any DAC.

"I was hoping for a simpler answer and a simple way f
of making sensible choices."

Listen to them both and pick the one that sounds the best.

That's too simple.