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
Interesting in that Soekris states

 "It have the fantastic clean and natural sound of a 27 bit R-2R sign magnitude DAC..."

whereas Schitt states

"If your 24 bit recordings actually have 24 bits of resolution, we’ll eat a hat. And those "32-bit" DACs? Well, they have this measurement known as “equivalent number of bits.” This means, in English, how many bits of resolution they really have. And that number is 19.5. And 21 is better than 19.5, in all the math books we know."
Post removed 
16 bit for every problem,<100 dB resolution happy home.
17 kHz on max natural frequency in nature. The higher the resolution, the deeper the sound image of the natural sound section.

It can’t. John Atkinson review of the DAC clearly states that while the analog performance is excellent, the digital performance is less than desirable especially on high signal levels (which is the majority of pop rock music).

Hello @shadorne 

Please allow me to preface this post by stating I am *not* looking to be argumentative (with you are anyone else). And I do know you are aware that I have recently purchased the Yggy, and sincerely appreciate your feedback in another post of mine. :)

Your response to the OPs question "How can the DAC be 21 bit if the chips are 20 bit?" technically does not answer it. Irrespective of what JA claims, Schiit - the manufacturer of the product - clearly states "Yggdrasil is the world’s only closed-form multibit DAC, *delivering 21 bits of resolution* with no guessing anywhere in the digital or analog path. "

So, wouldn't you agree that at a minimum the Ops question should be posed to Schiit? Seems to me they - and not me, you or Atkinson - would be the best people to ask.
@gdhal

I don’t want to argue either. I posed a simple question in the OP. I got some good answers, but was also viciously attacked by some aggressive individuals here.

One’s logic almost compels one to ask: how can you get 21 bit resolution out of 20 bit DAC chips. Since independent verification is essential in science and engineering, JA’s (and other people’s) measurements are crucial. That is why we have reviews.

You are not against independent reviews, are you?