An Update.
Bought a Schiit Freya, as I have been very happy with their other components. I purchased the upgraded Tung Sol tubes from the factory. It has been running about 4 hours, but based on my impressions so far, it will be going back. My initial notes (including swapping the 750 back in and out to make sure I wasn't nuts).
1) Where did my gain go? The Adcom if anything has too much gain. The Freya in passive seems to to missing about 3-6 db in passive and jfet mode from the Adcom (to where I was maxing the volume on quieter CD's, something I have never done with the Adcom). This is with XLR connections in and out.
2) Despite being rated at 14db gain for the tube stage (same as my Adcom), the jump from passive to tube is much smaller than the adcom from passive to active. I don't mind that, and prefer it, but I am wondering if they changed it from the initial design. I had emailed them about the gain in tube asking if it was the same for XLR and RCA (they said 14db for both), it is not. It is 6db less for RCA, same as my adcom.
3) Sound:
a) Passive- Unoffensive, lacking dynamics, and a bit veiled. The Adcom sounds like someone just removed grunge in comparison when in active and has better dynamics in passive.
b) Active- I am grouping these, as from my initial listen, aside from volume the Jfet mode and tube mode sound very close. Dynamics are much improved from the passive mode and about the equivalent of the GFP-750 in passive mode. The grain is better, but still there, and there is some midrange shoutiness. Soundstage may be slightly better than the Adcom, but my room has some imaging problems I am still working on. Overall the Adcom is blacker, you hear into the music further and when in active mode, it has much stronger dynamics (which is a good thing for maggies).
I am going to let it run in for another 24 hours to see if there are any significant changes, but as of right now, I am not excited about it. I was really looking forward to trying this preamp and had high hopes.