The CS8412 arrived yesterday. Late last night I installed it and the first 12AX7 I could scrounge into the CAL Sigma DAC. The installation process was relatively painless. What I've observed is that the Sigma wants a good 45 seconds upon being powered up before it will do anything, but then it locks on to the SPDIF output from my Edirol USB interface with no drama at all. I've had it running most of the day today and I've observed a few things: First, the sound is quite good. In fact, other than having a slightly hotter output, I can't barely differentiate between it an my Quad 99 CDP-2. Not bad for a design originally from 1990. Of course, the similarity in sound might have more to do with me having tin ears. Secondly, it runs surprisingly cool. The 12AX7 kicks almost no heat at all.
I'm not sure what I'm going to do with the Sigma yet. Maybe I'll tuberoll (lie) or chip-roll (bigger lie) it. As of this writing I have ...six DACses in the house. I'm becoming Dinny writ small. In any event, this first blunder into DIY was relatively painless, even if it was essentially a training wheels session.