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
@almarg



As always I agree with pretty much all your comments.

I would add that the 24 bit will always look much better because at the same -90dbfs you have more bits to characterize the signal. The 16 bit looks square because there are only 2 bits to describe the signal. Even with a 20 bit DAC there are 6 bits available to characterize the sinewave at 24bit (so it looks smooth).

The zero crossing errors are the most alarming in those particular measurements.

"Audibly insignificant" depends so much on the frequencies. Low level noise distributed evenly and randomly across the spectrum is harmless. Rounding or Truncation can lead to high frequency noise of distinct tones which is harmful even at low levels which is why studios go to lengths to dither digital when reducing bit depth.

JA notes the jitter performance is less than desirable also. There has been much importance given to jitter even though it is very very low level noise - and this is because non-random jitter creates distinct tones that are not harmonically related to the music. 

What is actually audible as distortion is very much related to tone and frequency rather than purely a signal level.
@almarg 

I'm very appreciative that you would chime in on this thread. I don't want to speak or write on the OPs behalf, but he too should be.

All -

I'll up-the-anti. I'd like to suggest for the moment that you forget entirely about measurements. I don't care if its voodoo. The Yggy sounds spectacular. Please read my last post in the New Yggdrasil - First (and second) Impressions thread.
I would hazard a guess that for several reasons (only 20 bit, R2R and no upsampling), by necessity the filtering in this DAC will be close to Nyquist and therefore quite aggressive or sharp (like Non upsampling CD players). I suspect it is this smoother sound from filtered highs and the fantastic analog section that makes this DAC so musical and desirable to some folks over competing ESS 9018 and 9028 style DACs.

Measurements only validate accuracy or high fidelity capability of a device. The musicality aspects are all in the ear of the beholder.
@shadorne 

You are correct that measurements only validate accuracy or high fidelity capability of a device. The musicality aspects are all in the ear of the beholder.

In my case, there is something else noteworthy.

I already have a "virtual" Benchmark DAC 3. I call it an "Oppo UDP-205". It, has a MEASURABLY BETTER AND MORE ADVANCED DAC chip than the Benchmark.

Some folks might now write back and cry foul; reminding me that the DAC chip itself represents only 20 percent of the story, and that the implementation of said chip, analog stage and grace of God comprises the remaining 80.

I will then write back and point out that because the Oppo uses a Sabre ESS9038 instead of an ESS9028, that my 20 percent should really equate to 30 percent.

And away we go.

@gdhal 
 
The Oppo UDP 205 is indeed outstanding and I expect that it sounds a bit brighter and thinner than the Yggy. It may well outperform the DAC3 as you claim. Perhaps the Oppo UDP 205 will be another Class A or A+ Stereophile recommended player. Per JA above, we can easily surmise why the Yggy is not.