I'm a "picky listener" but don't have "golden ears".*
I've NEVER heard ANY defect from a DAC (or a soundcard, or CD player, or AVR, or anything with a built-in DAC)
EXCEPT when I've heard NOISE from a soundcard. For example, I've had a soundcard that put-out noise when the hard drive was accessed (or maybe there was always some audible noise that got worse with the hard drive... I don't exactly remember).
* When I was younger, I used to THINK I had exceptional hearing (and my hearing
was probably better when I was younger
) and I was sort-of an an "amateur audiophile" on a budget, always trying to improve my stereo. But the real deal is, my hearing isn't better than anybody else but most people just don't care as much about sound quality and they don't give it much thought. Back in the vinyl days, the clicks & pops drove me nuts and most people didn't seem to care as long as the record didn't skip. (Of course I knew it didn't take golden ears to hear
that!)