At the same time I took receipt of the EL Stack, I got the OLDAC. After having spent a couple days with the EL Stack, I switched to the OLDAC.
They clearly went for a simple design when conceiving this. Unlike the EL Amp and EL DAC, it's a simple block of machined aluminum. Even so, it's well-built, substantial, and attractive, if simple. The fascia has a nice brushed touch to it.
The front features a switch that changes inputs from USB to optical, and vice versa. The power switch has good throw and a click once you pass the actuation point. Power light is green, but this is all minutia.
I have no complaints whatsoever about the build on this, it doesn't scream quality, but it gently whispers it in your ear.
The OLDAC was tested thus far with the EL Amp and Sennheiser HD 598; I will test with more headphones as the review period continues.
The back features USB and optical inputs with RCA outputs. It takes a 12VAC power brick.
Now the relevant part, sound. Coming from the EL Stack, I found that they were very, very similar, with a little bit of a downgrade. I noticed, particularly with my HD 598s, that the "Sennheiser Veil" had returned, not in full, but noticeably. It seemed to be a little bit less detailed, a little bit more closed, but still wholly enjoyable. As a standalone DAC without a comparison point, especially something in the EL Stack's price range, it fairs very well.
Bass seemed just slightly bloated around sub-100Hz range, but that could be an impression that disappears over time, and I will update when I write the full review. Treble is relatively detailed, but seems a little less airy and open than the EL Stack. Mids are fairly lush and warm.
I'll continue to listen analytically over the next few weeks and better form my opinion before the review is released in full.