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
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". :)

I ’think’ it even sounds better if run with a source prior to a listening session, even if is left on all the time (as mine is).

Not sure if I could reliably tell either way - maybe it’s my own little placebo... :)
A question for Yggdrasil owners: do you still use the stock power cord provided with the unit or have you substituted another cord? 

I substituted the power cord immediately. I also removed the very 'basic' footers.