Which DACs are known to be sweet/rich/relaxed?

@robert1976 If 95% of the recordings sound fine, you are seeking a solution for the 5% that don’t. A solution that makes those 5% sound fine may adversely affect your satisfaction with the other 95%. I reiterate my view that a software or hardware approach to reducing treble energy for specific albums is a safe approach.

Acoustic treatments may help reduce the excess brightness and hash from those 5%, but they might unacceptably dampen the sound of the other 95%. Either try treatments that can be returned or consider hiring a capable acoustic engineer who knows how to treat a room.

I would also consider some of the highly cost effective, simple suggestions made by others - get a better Ethernet switch; try different Ethernet cables. Those, in particular, can make a very audible difference, but again those solutions affect everything, not just the objectionable 5%.

Good luck.

This post has gone off of the rails!! The OP wanted to know, "Which DACs are known to be sweet/rich/relaxed?" We have debated nuclear physics and acoustical engineers for room treatments. If you treat your room, your system will still not "warm-up"! If you have an extremely bright pair of speakers, their brightness will be amplified by creating a perfect acoustical chamber since you truly hear what the drivers deliver. We all spend far more than we should on equipment to recreate a jazz club in our living room. How many jazz clubs are acoustically treated by engineers?? I love the interaction of tables, chairs, glasses, etc., on sound quality. That's what makes the music real!!

Aries Cerat DAC or Audio Note, AN being much warmer. End game and call it quits for the next 7-10 years. Or, spend $200 K (in this crazy economy) and build a custom room designed by engineers and still question, "Which DACs are known to be sweet/rich/relaxed?" because my room is so perfect!!!

Best of luck on your journey! BTW, great system!! 

Acoustic cannot replace bad gear... It is trivial fact...

But the best gear in the world will not be so great in a bad room, this is less trivial fact...

And the room acoustic can be design to compensate in some way to some degree for some design limitation or accentuated qualities of the gear... A room acoustic can be tailored made to a specific system ... This is a way much less known fact...

And acoustic can be low cost and very good even if not perfect ...No one know that save those who had accomplish it...

I think 5% sounding bad is a symptom that all recordings are being reproduced sub optimally. At least in my experience, as I shifted the overall balance such that the emphasis of different parts of the audio spectrum came in line, then all recordings sounded better and the outliers did not sound shrill or annoying. You could still tell they were bad recordings, but they were not offensive.

Pursuing the high end has an nearly endless learning curve. Thirty years in I was nearly clueless after thousands of hours of learning. Now at fifty years… I hear levels of nuance I was completely clueless of twenty years ago. For instance… this subject… I completely understand… it is a subtle but really important parameter in realistic sound.

Another vote for an Acoustic Research solution. In my case I replaced my Esoteric K03Xs because it was sharp on the leading edges, no matter what cables amps preamps or speakers. I was lucky to find an AR Ref CD9. This is an all tube affair and significantly fixed the problem I’d had. All of the highs became clear transparent and never harsh. I use the DAC for streaming via coaxial and find it so much better than the onboard DAC in the Pioneer N70Ae.

The CD9 plays into a SS AR LS10SE and Luxman M900u to a pair of large horn speakers with super tweeter. No harshness or sibilance at all but lots of airy highs.