all tube preamps are not created equal. some of the newer designs sound like solid state. for example, i reviewed a recent mcintosh tube preamp and called the company to suggest that i could not identify and tube-like charcter and a technician siad the preamp was designed to be as "neutral" as possible, i don;t remember the model number, but it used 2 12ax7 in the line section and 2 12ax7 in the phono section. retail price was about $3900.
then there is the vintage tube sound--i.e, having a euphonic coloration, but clearly inaccurate by todays's standards.
so when discsussing tube preamps, the degree of tube flavor is an important consideration.