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
It does. I researched them for a while but since it is new in the marketplace there were obviously no reviews. I ended up going with the Holo Audio Spring Dac but couldn't help but think for the money the Soekris represents a great value. Hope you enjoy it!
I do, love it.

While i tend to switch between the Soekris and the Yggdrasil constantly (depends on the style). Im waiting for the Spring DAC :)
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."
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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.