I’m not sure if this matters but if you think about it, a typical preamp amplifies millionth to volts so a thousand or so times but an amp just takes volts and amplifies less than 100. The pre amp does more “work” & is more susceptible to distortion & extraneous noises because the signal they deal with is so much smaller.
Preamps can color sound considerably. Surprising?
Had the pleasure of listening to 4 hi end preamplifiers this weekend. And each preamp sounded very nice. But they were different. Each preamplifier has different circuitry and within the frequency spectrum there was more vibrancy in some areas versus other areas. Amplifiers are the same way.
It takes a while to appreciate sound differences between preamplifiers. And then you got the issue of Breakin which further changes the color.
clearly designers are playing around with all the internal circuitry in a manner that hopefully will be appealing. Clearly, these units do not get out of the way when it comes to moving a signal through the box.
I think solid state is more susceptible to coloring versus tubes. Tubes color sound as well.
It's all about marketing different ways to color Music. This isn't necessarily bad but it's never really talked about this way.