I upgraded to a Topping D70s from an airist audio r2r. And I was simply astonished at the improvement in tonality, stage, depth, separation, clarity, air (all the typical buzzwords, etc). Not really comparable, very different topology associated with the D70s, but it still sounds “r2r” in many ways (Not just my opinion). This one uses two AKMs -one per channel- not a single chip, so maybe not in the category you wanted here. But -as everyone here probably agrees - so much of the cool stuff is in the output stage in combination with the chip output. The reason I got it was for its excellent reviews, good price, and great digital input variety (was looking for I2S to be included). At this point, I can’t imagine upgrading with very much improvement until getting into a Denafrips Pontus II or something else in that offering (or higher).
AKM makes the best DACs
OK, before you flame a reply to my heading please read this section.
It is a terrible idea to judge a DAC based on the chip. I don't think consumer's should ever do that. I think there is a lot that goes into a good external DAC unit and the converter chip is just one of many factors that go into the final sound.
Having said that, it turns out I tend to like the sound of DACs with AKM chips over most others. A long time ago I would have said the same about Burr Brown.
For converters which use an all in one chip what is the brand you find yourfself more likely to like the sound of vs. not?