I recommend you keep it on SLOW. I imagine you would need a very muddy system to justify the SHARP setting. The X20 got a few days of breakin before it reached me, but so far this is the least fatiguing Sabre DAC I've heard yet (and I recall Stu saying treble fatigue was absent as well). I always thought my Yulong D18 deliberately rolled off the top in an effort to mitigate treble fatigue common in Sabre DAC implementations. The whole first week I was bracing myself for a pitchy note in a rough recording that would rip my ear drum. It just isn't happening, and I'm using the U18 over AES (not the PUC2). I'm not sure how it's achieved but the X20 has been far "safer" [for lack of a better word] to listen to than my D18. The D18 always reminded me I had aluminum tweeters and the X20 has been in great form with both aluminum and RAAL. I've always wanted to try speakers with beryllium tweets but my front end couldn't even tame aluminum until now. Other first impressions it made on me was sick channel separation, instrument/vocal layering, and depth. Just put the battery into the remote today. Having all those buttons on the remote is way faster to work with than the single clickable dial.