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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
gdhal's avatar
gdhal
1,641 posts
 
I just found this post/quote from Mike Moffat and it appears to directly answer the OPs question.

https://www.head-fi.org/threads/schiit-yggdrasil-impressions-thread.766347/page-123#post-12342937

"Two twenty bit DACs (one per phase) double the resolution for a balanced signal. Double the resolution only adds 6db (one more bit) for a total of 21 bits. In this case, 20+20 equal 21."



georgehifi's avatar
georgehifi
4,966 posts
 
Just as a side note the AD5791 is close to $100 and the ESS’s around 1/10th of that.
Looks like the AD5791 took over where the PCM1704 left off.
PS Loved the video interview with Moffat and Stoddard.
Cheers George
defiantboomerang OP
141 posts
 
@gdhal 

great find, thanks. 
defiantboomerang OP
141 posts
 
@gdhal 

great find, thanks. 
gdhal's avatar
gdhal
1,641 posts
 
You're very welcome @defiantboomerang. 
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