@hilde45 I hope you're able to audition the XP-12. You and I seem to have somewhat similar listening preferences. You mentioned violins as a benchmark and how your tube preamp leaves you wanting more detail and leaves you thinking you're missing some of the top end. I find the same is true when listening to an acoustic guitar with some, not all, tube preamps. And acoustic music, with no amplification and in a great venue, is a great yardstick to use in testing gear. I use a solo acoustic guitar recording, a solo piano recording, both jazz and classical, as well as big bands and symphonic works when I try out gear.
A number of people who posted comments have dissed the concept of neutral. A simple view of neutral is that a device (preamp, amp, dac, speaker, cables, whatever) does nothing to change the recording. It's not complicated. It's why people with high quality gear note that if a recording is poor in quality, or vinyl is poorly pressed, they hear all the defects in the recording. It all gets passed through by their gear. The gear provides a very high level of detail and accuracy to the recording. The frequency response is flat, with no emphasis on any frequency. Audible distortion and noise are virtually non-existent. The device plays back a signal that is true to the recording. To me it's much easier to accomplish this with electronics than it is with speakers or your listening room.
What matters is what sounds best to you, me or any individual. Our listening rooms introduce anomalies, distortion, reflections, etc. Our hearing does the same. So we can start with great gear and still end up with issues. But the concept of neutral is not complicated. And not everyone likes what I've called neutral. There is a large following on this forum of folks who love the "warmer" sound of some tube gear. I respect that and understand why, as I own a tube phono stage and a tube amp, the latter in a secondary system. But that "warmer" sound is typically not neutral, with an emphasis on the midrange.
Everyone should just respect that we each have preferences as to what sounds best. And as others have noted, it is important to consider the compatibility of one piece with another. It's one reason why I think the Pass Labs XP-12 would be a great match for your Pass Labs amp. Pass designs its gear to work together, with preamp output characteristics compatible with their amps' input.
Hope you find the solution you're seeking.
