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
Robert Harley is the one who reviewed the yagdrassil dac, he is a very good and accurate reviewer, for Absolute Sound....
A question for Yggdrasil owners: do you still use the stock power cord provided with the unit or have you substituted another cord?
I'm using the stock power cord. 

I substituted the power cord immediately. I also removed the very 'basic' footers.
Hi David. Were you able to detect an audible difference with either the (ones you use in place of stock) cable or footer?

I'm sure you read the manual. The Yggdrasil has "zero stick-on feet (because Yggy already has screw-in feet—you’ve reached the big leagues now, guys)" 

Just a little humor :)
Yes on both counts. I was expecting the differential with the power cord, but I was more surprised at the improvement made when I swapped in footers which was after the power cord swap.

I've posted this elsewhere...the Yggy is designed to a price point and is exceptional at that price point...but the good/bad news is that it will respond to changes such as power cabling and isolation, etc.
Post removed 
Thanks, David.
I just saw your response, but answered my own question earlier, right after I posed the question on here, by putting in an old ESP cord, circa 1995. I only wanted to change one thing at a time, or I’d have put the Shunyata Zitron Python on the DAC and another cord on the Arcam player. My rule, though is, One change at a time! Came back two hours later (as you probably know, cords should have time to "settle", although people scoff at that [ and I ignore that, since I KNOW that I can hear the difference between 5 minutes and two hours ]). Sure enough, it made a difference, even with a 20 year-old vintage - but quite good - cord. I’ll eventually put a Shunyata Python Zitron on it, but not now. As for the footers, I’ll do that again in a week, when I have listened to more music. Still points for now or maybe Nordost Sort Futs, althought the Townshend is - in my experience - the one that kills off the most vibration. I have used the two in combination, but not with a converter as resolving as the Yggdrasil. Since I don’t have balanced outputs on the CJ preamp (which I’m not using yet anyway), I want to give the converter every other advantage I can. Even as it is, being only 5 days old, I played Marianne Faithful’s CD of Kurt Weill’s The Seven Deadly Sins and could hear the piano pedal release waaaay back in the soundstage, something I hadn’t even been able to hear when I had a First Sound preamp or any other components I reviewed along with my own Hurricane amps (still love the realism they are capable of) years ago. Given I’m just using an NAD BEE integrated, I expect to be cross-eyed with admiration when I make that changeover.
I’ve had much more expensive digital in my home than the Yggy back when I reviewed components for TAS, Ultra Audio.com and Fi Magazine, but nothing that rivaled the Yggy in both resolution AND the musicality - and even though it’s FAR from broken in - I suspect a rather spectacular end result with the all-tubed system. I will probably buy another Townshend Seismic Platform, as I have found that to eliminate ALL airborne and structure-generated vibration. The nicest thing so far is knowing that the tonality of instruments will mature further (the upper midrange-lower treble "bite" is still apparent, but doesn’t bother me at all). Nordost’s cables take what SEEMS forever to get rid of the upper midrange glare (at least, as I’ve said in previous thread, 4 weeks 24/7).

Thanks for the response. I appreciate that.

And Gdhal, as you can tell by my response, yes, there is a rather noticeable difference when removing the stock cord. I’d suspected as much, but wasn’t sure of any conclusion until I actually did the experiment and decided that , as old as the ESP cord is, it is FAR better than what comes with the unit. I’ve loaned a friend a Nordost Heimdall cord, and I’m afraid he’s going to have to give it back it for a week or two (he won’t be happy with that, as he’s become used to the sound of his system, and he’ll notice it immediately, but hey, it’s on long-term loan to him, and he’ll just have to suck it up)! I’m pretty generous with my friends, foisting off equipment I have too much of. The only problem is that by the time I ask for it back (if ever), they’ve heard the improvement. By then, they’ve become involuntary audiophiles without meaning to! I let them hear everything I buy. This friend has heard the Townshends, both the Iso-Pods as well as the Seismic Platform and lusts after them. He’ll get one of the two eventually. But he’ll never spring for the Yggdrasil even if I take it over (and I have no intention of unplugging it, although I have an ac converter in my car, and it would take literally 30 seconds to get it out to the car. But he’ll hear the improvement, nonetheless). In fact, on Head-Fi. org, a guy decided to see how long it would take for the sound to "return." He left it off for 5 minutes and then an hour (and then two hours) and said the sound returned within two hours. Here’s his post:

"So tonight is the night. According to my very vague calculation, I was at over 1030 hours of 24/7 music play on my Yggdrasil. As promised a while ago time to turn the damn thing off. So, after this dramatic event, did music, the way I knew it, die?

5 minutes off - no sound changes really. Ok forget it, let’s do this properly.

1 hour off. Dead cold. Back to life. Right off cold the treble was a bit harsh and the rest of FR a bit disjointed. Got back to it less than an hour later (still cold to touch) and the bass, impact, speed and details were all there. The mids were butter smooth, detailed and deep reaching like before (HE-6s/Eddie Current as we know it) and the treble already great. First minutes aside, I don’t think Yggy went back to the first days’ more dubious sound. Two hours later, it’s lukewarm again and it sounds pretty damn impressive already.

I had an warmed up Theta Gen V on the side for comparison and ready to switch over to for a few days, if the sound was crap. But it’s not.

YMMV. FWIW. WTF. etc" [End of his post]



So, this might help those who are afraid to unplug it ( Me? I was FRANTIC trying to get the very stiff ESP hooked up before I "lost" the already stellar performance it delivered after 5 days!) So his post gave me hope. Mine was only unplugged for 2 minutes.