Finally got around to testing AD797, mostly comparing 2 x AD797ANZ (on BrownDog 021001) with 2 x OPA211 (on BrownDog 020302) and OPA2211A (on BrownDog 970601) and LM49722MA (soldered onto DIP socket). I was testing all of these parts in the output stage of my (highly modded) Eden Highwayman bass amplifier. The input section uses OPA827s and OPA211s. The EQ section was bypassed during testing. The preamp section employs +/- 16V power rails.
My quick impressions are that AD797 sounds relatively clean and neutral, though a bit darker than OPA211/2211A. It's a bit hard to describe, as it doesn't really sound veiled, just lacking in "sparkle" in the highs. Although I haven't done a proper comparison, I'd say that they are more neutral than the AD825 (which I initially liked, but later found a bit too colored, as they seemed to suck out the mids somewhat, boosting bass and treble). Sort of "clear and a bit dark" if that makes any sense....
Although I didn't notice it in previous testing, I found that the pair of single OPA211s sounded somewhat clearer than the dual OPA2211A, which sounded somewhat more distant and less authoritative. Definitely prefer 2 x OPA211.
From a limited comparison, I found that the LM49722 is somewhat better than LM4562 (cleaner/less colored), though lacked some of the openness found in the OPA211/2211A. Maybe less sterile than LM4562, too. I do like the clarity of the midrange of the LM49722, however.
Still have more listening to do with LME49860NA (which I listened to briefly), and ADA4898-1 (when new BrownDog adapters arrive). Quick impression was that LME49722 was superior to LME49860.
From the charts above, it appears the the OPA-Moon generates a significant amount of harmonic distortion.... which might make it sound "tubey" to some....
