I will never know how the first three hours of the yggdrasil sounded as I let the DAC warm up for an hour and proceeded to make technical measurements. If the measurements presented are familiar territory, then you should be as impressed as I am. If such graphs are not familiar, then please note that these graphs are  extended, some down to -160 dB for example. Extreme. Much farther than most other graphs you will see elsewhere on other DACs on the internet or in brochures. So be careful when making comparisons. Watch the X and Y axes in other data. The graphs presented here are not marketing graphs. They have not been prettied up as is often the case in mainstream consumer goods.
 
Schiit has specifications for these measurements published on their website and in their operating instructions. In my measurements, my yggdrasil measured better than Schiit's conservative specifications in every single measurement. Every single one. Well done Schiit!
 
Commentary added to the end of this post.
 
The data presented were collected as follows:
 
1.  PrismSound dScope III, picoscope 2205, FLIR E63900
2.  DAC balanced output used for measurements except oscilloscope square wave response which used unbalanced output
3.  100 Kohm load used for measurements
4.  44 KHz  sample rate, 24 bit depth
5.  USB input - cables to go USB cable
6.  Balanced cables Tecnec Canare starquad Neutrik XLR cables
7.  Unbalance cable BlueJeans Belden RCA
8.  Vaunix Lab Brick USB hub
 
Commentary:

By now, some of you probably have noted the THD+N graph may not be the lowest ever seen.
 
The THD+N graph measures artificially high due to a driver / OS interaction on my computer. An update will be forthcoming.
 
Designers are often faced with trade-offs for various reasons. I believe the Schiit design team has made trade-offs that result in best auditory experience over best measurements possible on all fronts. I have a colleague who gives a "13 dB miracle" demonstration showing that SNR isn't the best predictor of auditory experience. So THD+N may not be that influencial on the final sound while jitter may have a bigger effect. Those of you who will reference the 1992 and 1998 AES papers on the topic of jitter may note that no trained subjects were used to determine the masking thresholds. With many more listeners now well experienced in digital audio listening we might see much lower thresholds if the experiments were repeated today and trained listeners employed.

Yggdrasil measured at 408 hrs on time.

Test setup is same as described for the measurements taken at 3 hrs on time with the following exception: A PicoScope 5243B was used in place of the 2205. The 5243B has 15 bit 2 ch ADC capability and higher sample rates than the 8 bit ADC used on the 2205.

I will try to include a few extra screenshots though this posting system only allows 8 per post and I only reserved two posts for these measurements. Most measurements were so close to the original to be considered of no consequential change. Except one spectacular change. If the 3 hr on time jitter spectrum was impressive, take a look at the 408 hr on time jitter spectrum. OMG! My congratulations to Mike Moffat. That is a truly impressive achievement!

The THD+N graph measures artificially high due to a driver / OS interaction on my computer. An update will be forthcoming.

Yggdrasil measurements at 408 hrs on time, part B.
I have included a 1KHz -70 dBFS time domain signal to demonstrate that the blib seen in the -90 dBFS version is pretty insignificant.

Crossover distortion.

Crossover distortion.

Indeed, not very severe though.
All 'normal' ladders have it in some severity.
Only with signed magnitude it isn't obvious as it isn't in the 0V line, instead it has 2 of them at the -6dBFS points.
It is only possible to 'see' it when you zoom in on that point. Nobody is going to.
It may be less audible in SM because in softer passages as there is no 0 crossing and the signals would be well below -6dB or even -12dB.

impressive jitter figures...