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

Showing 5 responses by nugat

It's really striking when audiophiles ask engineers to tell them how good something sounds. I'd love Stereophile to put on their bench a Guarneri 
vs a Stradivarius. My next concert will be incomplete without precise measurements.
JA is wrong, Schiit uses rounding, not truncation.
JA believes that MQA (lossy, proprietary, licensed platform)
is " the birth of a new world".
The "extra" 1 bit in Schiit balanced multibit Dacs is deducted from the 2 phases +6dB.
After a failed appeal to authority now  comes a referral to youtube and arguing ad hominem. Scores of other logical fallacies still at hand.
Mike Moffat knows a thing or two about DACs  since his theta digital dac in 1988  and MoFi Gain system. Introducing dither to Yggdrasil is a software change. He chose not to do so because with the 20 bit chips there is no significant difference between rounding and dither. Last but not least  let's not forget that there are hundreds of milions of digital tracks in 16 bit in distribution and only thousands in higher resolution. 
The video from Nigel Redmon is all clear and right on truncating /rounding, especially with the examples of going from 24 bits to 16. To get his whole message it’s worth going to his site and read about dithering. When and where to use it to make recordings sound better. Surprisingly he advises against dithering at many stages of production.