The thinness of some SS preamps is what it sounds like,thin.Good tube preamps come much closer to what I consistently hear live without question(there is color ,tone and developed fullness that`s unmistakable). But I certainly accept people will always hear differently and have other opinions,SS pre/amplifier for you,tubes for me.
No live instrument or voice I`ve ever heard sounds thin ,lean,dry and sterile(incomplete signal reproduction? who knows).If the fuller tonality and realistic body is a tube coloration I `ll take it as it`s more authentic natural and more convincing.Thin and sterile is`nt(sounds hifi and canned to me).That`s why there`re ample choices available to please very different ears.When someone hears a live instrument that sounds "thin" let me know.
Regards,