Schiit Yggdrasil -- 21 bit?


Schiit says that Yggdrasil is a 21 bit DAC. But the DAC chips that they put in the device ( Analog Devices AD5791BRUZ, 2 per channel) are 20 bit with the error of plus-minus 0.5 LSB.

How can the DAC be 21 bit if the chips are 20 bit? Using two chips per channel does reduce the RMS voltage of the noise by  a square root of 2. But how can you get to 21 bit from there?

Can someone please explain.
defiantboomerang
@gbmcleod I’m in the camp that finds the Yggy needs time to break in. A week will be a good start. I suggest 3 weeks. (This is for a brand new Yggdrasil).
David, I agree.

Anecdotally, last night, I had friend over who ONLY LISTENS to the Chicago Orchestra’s Scheherazade. ONLY. He replied, upon prompting, "I think it sounds pretty good." I said, "We’ll listen tomorrow morning and we went to sleep.
We heard it again this morning and it had lost some of the dynamic compression, which Dave heard immediately. 3 days down, 5 to go. Nordost takes a month.I’d be ungenerous - not to mention foolish - to not allow the Yggdrasil its full time to blossom. I hear small vaporizations of dynamic compression, especially on lower midrange instruments. Fear not, it’ll have as much time as it needs.

IMO, whenever you plan to listen - even after break-in - it's nice to have run the Yggy with a source for 30 minutes to an hour prior to your listening session.
IMO, whenever you plan to listen - even after break-in - it's nice to have run the Yggy with a source for 30 minutes to an hour prior to your listening session.

+1!

Most bands have an "opening act". Prior to my listening to a live recording of a two to three hour show, I throw something on. This flies in the face of those who intentionally leave the Yggy on 24/7. I do not. I power off/on each listening session. I suppose if the Yggy were left on 24/7 it could forgo the need/desire to "warm it up". :)