Doing some initial comparisons now of the Soekris dac1101 and MHDT Labs Atlantis going into a Schiit Sys then the ampsandsound Mogwai.
The first challenge is volume matching. The Soekris needs to be turned down a bit from max or it's louder than the MHDT.
The Atlantis has two AD1862N-J chips (R/2R, of course) and a tube buffer. The tube buffer is currently using a Russian 6н3п-др tube. It is currently being unfairly fed BNC from a Mutec MC-3+ Smart Clock USB. I'll do direct USB tomorrow. It's been turned on for a day or two straight.
The Soekris dac1101 is using the stock USB cable coming from my motherboard's USB DAC-UP ports that theoretically provide clean 5V power. It's been turned on for 30 minutes.
Both offer a nice organic sound. The Soekris does not sound like a Delta-Sigma DAC. It has a good deal of the timbre of resistor ladder DACs. I can already tell you that I like the DAC part of this better than the Schiit Bifrost Multibit. I found the Schiit to be a little grainy and slightly harsh despite many users commenting on its warmth.
I'll have to let the Soekris stay powered up and playing music for a fair amount of time. Comparing a cold piece of gear to one that is warmed up and fully burned in is kinda mean.
Since I don't want to leave you hanging too much, I'll say that the Soekris feels like it's compressing the music just a bit compared to the MHDT (so it's less dynamic). It's a little brighter (expected), which will be more to the liking of many. It is not bright like a Sabre, but brighter than a NOS dac with a tube buffer (like all of the other dacs in the world).
The soundstage on the Soekris isn't as deep as the MHDT but it's about the same width. The sound presented by the Soekris is far from thin, but it's not as full as the MHDT. It's a little more analytical versus the musical Atlantis. Again, I'd be incredibly surprised if it wasn't.
Most people would prefer the slightly more analytical and less-warm sound of the Soekris compared to the gooey and warm sound of the Atlantis. Most would prefer the depth of soundstage and dynamics of the MHDT over the Soekris.
So far the feeling of compression is my only complaint about the Soekris dac1101. I didn't notice it at work because I couldn't instantly swap between DACs. It might improve as the unit warms up and/or burns in. Right now, when I switch away from the Soekris, my ears relax a bit and I feel like I can breath more freely. By compression, I really mean two things: One is that it feels a little closed in, and the other (which is probably the cause of the first) is that the volume of instruments seems closer together on the Soekris than on the MHDT.
As far as tuning the sound to your liking, the Soekris has 4 filter options that you can cycle through at the touch of a button. This is awesome and I appreciate that companies are starting to provide this option (I've also had two other DACs that did it: the Audio-GD NFB-2.32 and Emotiva Big Ego). I believe that you'll also be able to tinker with the firmware of the unit (not sure what that does to the warranty) since you can do so with the DIY versions of the Soekris gear.
The MHDT Labs Atlantis can be tuned in a couple ways. First is that you can choose three different firmware options for the USB input if that's what you're using. The changes are very subtle. The much more significant tuning option is tubes--you have dozens of options, and each impacts various parts of the sound in different ways.
You can also tweak in front of both, but I won't talk much about it. The important thing to note is that USB is the only input on the Soekris dac1101 and it is always powered by USB. The Atlantis is powered via a power cord and accepts USB, BNC, RCA, and TOSLINK.
So far, the Soekris dac1101 is very good. Is it bested by my $750+ DAC that is much larger, has no amp, and has an $1100 USB->S/P-DIF converter in front of it? Yep. But I already prefer it to the Schiit Bifrost Multibit and would probably recommend the dac1101 as the best entry into R/2R that I'm aware of. Small form factor, integrated headphone amp, filter options, line out, good price.