I had to learn a few things at first like going into my interface with an XLR (I figured balanced was a better line) meant going through the Interface Preamp == Tone Suck.
So I needed to go LINE in. But the problem with LINE in was the DAC conversion was noticeable compared to the SPDIF.
I figure if you can really hear the difference. So was it the KPA DAC or the Apollo's ADC or the combination?
Since the SPDIF sounded like what I was hearing in headphones AND the KPA had to do a DAC for that, it must have been the Apollo, is my guess.
Bottom line, SPDIF was the bomb so I stuck with it. Apollo has an optical IN that is not RCA so I had to get a conversion box. AND I found out that for some weird reason, this same routing worked for the Clarett but NOT the ID22?!?
In any case, it has me thinking a lot more about ADC/DAC and what a really good unit would be, and what cost would be worth it. Not for the KPA, but for a tracking chain.