In my DAC reviews, I am testing for "macro effects." That is, how the system as a whole operates. I don't dig into intricacies of the DAC chips themselves as they are so proven these days that the issues are mostly all in implementation.
Here though, Schiit uses a DAC chip not designed for audio so I thought I dig in and see if I can find any corner cases. As luck would happen, I immediately found a "micro" issue with any input signal that is a multiple of 100 Hz. Here, I show what happens when you feed the DAC initially 9999 Hz and then 10,000 Hz:
View attachment 18322
The moment you click up the frequency one Hz to 10,000, you see distinct pattern of 100 Hz components across the full spectrum. Further, the noise floor goes down, making them appear more easily.
I tested this up to 192 Khz and it is there at all sample rates so it is not the Schiit filter. It must be inherent to the design of the Analog Design DAC.
To test this further, I changed the tone to -60 dB and got this:
View attachment 18325
Problem remains but frequency of the extra tones changes. The amplitude of distortion components does not change which means now they are only 60 dB lower than our main tone (rather than 120 before). So perhaps at the extreme this an audible concern. You have a form of dynamic distortion that only plagues certain audio samples in your music and not others.
Same test on Schiit Modi 3 shows no such issue.
There is a cost to ignoring 30 years of progress in DAC design and going with odd choices of silicon as is the case here. Carefully measuring prototype designs for such glitches should have been performed before deciding to proceed.
Anyway, we are deep in measurebating but I thought I share this.
Edit: lost a bit of text in the original post which I added back in.