Preamp Sibilance?

Hi all; first time here with a question that maybe I can get some input on.

prior to a recent purchase, my gear was an auralic g2.1 streamer feeding a sonnet Pasithea DAC feeding Triode Lab 45 monoblocks into some large Joseph Crowe horns… and this system sounded fantastic. 

I Wasn’t really looking for any sound changes BUT Then  I decided I wanted to try out adding a turntable to the mix, which meant I needed a preamp as a control unit and so looked for one that had a reputation of being transparent and not coloring the sound. I landed on the Halo Audio Serene Kitsune edition. With the Serene in place, For 90+ percent of the music I listen to this was a notable improvement including a step up in image size, bass weight, fullness, and resolution; however for that other percentage I now hear a level of silbilance that kind of ruins it for me.

the Serene has about 100 hours of playing time so far and I would have expected most of the break-in time to have passed.

Prior to using the Pasithea as a DAC/Pre, I had a Don Sachs Model 2 that I really enjoyed, but ultimately sold because I preferred the DAC direct sound. I heard no hint of Sibilance with the DS pre or with the Pasithea  by itself.

so I guess my question is, have others experienced this with either this preamp or with other preamps?

Is this preamp just not the right paring with my triode Lab 4wpc monoblocks?

is it possible or likely that more breakin time is needed?

Other than giving this a bit more time, are there other recommendations, such as swapping cables or interconnects. For reference all cables are duelund 16ga tinned copper cotton/oil.

Thank you in advance 

Glen