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

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.

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.

Good to hear some other folks own an Audio Research Ref CD9se… an incredible DAC that gets the details and nuances in order with exceptional balance and musicality.

Mine has really profoundly influenced the sound quality of my system in all the right ways.

I'll probably be castigated for this recommendation.

Before you do anything, install a dedicated grounding system and connect it to every metal case with a separate lead back to the grounding point rather than creating a daisy chain between pieces of equipment.

That should make a massive improvement, but to completely fix the issue, you'll need to do that same with all speaker drivers. Sometimes just grounding the frames or baskets isn't enough and it's necessary to also ground the magnets.

It that fails, then and only then consider changing equipment.