markd51 are you happy with the sound?
Yes, My Sigma II, and Delta Transport i bought back in 1997 brand new, and the Sigma II is a very nice DAC, tough to beat for the money that they sell for today. Very nice sound, full, deep bass, sweet tone, clear highs, but not etchy,or digital sounding, smooth sound, nothing missing from top to bottom with this DAC.
In fact, in many ways, I like the sound of the Sigma II better than the Alpha. It seems to have better overall balance, and it's voltage output seemed better, the Alpha was always known to be a Unit, with very high output voltage, something like 4.0v, and this seems to make the unit hit my pre-amp quite hard. It was said, CAL used to provide resistors with the Alpha, that could be soldered in, to fine tune output voltage. This was not needed with the Sigma/Sigma II DACs.
I also have a modded Delta, and Alpha DAC, which is currently in my system.
The Sigma II I notice, as have others, is less sensitive to Tube rolling. You could put a cheap chinese tube in it, and it sounds just dynamite. Of course a better tube will help the sound.
The Alpha on the other hand, is much more sensitive to tube rolling. And I've heard some claim that the Alpha was harder on tubes. I still have the original chinese cheapo tube that came with my Sigma II new, and was never able to wear it out! Nary a problem with that DAC either for all these years, they were well built. Often I have thought of selling the Sigma II/Delta, but seem to keep it as a back-up, just in case the Alpha ever goes kaput.
I could again, live happily with the Sigma II in my system. Mark