How to judge a preamp's sound

Thanks for the informed replies. They make sense. (And @russ69 I didn't get the sense they were throwing in amps at random.)

I have read so many posts where people discuss the major differences between amps that I figured it would be hard to estimate the character of the preamp across those differences. I imagined someone trying to describe the flavor of a bland meat in, say, a curry, a tomato sauce, a hollandaise, etc. But this analogy appears to be a bad one. Glad to know better.

It's easier to characterize the sound of 1 component if you can try it with many other components.  You will eventually hear a consistent trend.

My question is, Can someone accurately generalize about "the" sound of preamp across a variety of different amps? Wouldn’t the amps be enough of a variable to at least complicate the "character" of a preamp?

Yeah, I’d agree with that. While it’s certainly interesting to hear how a pre might pair with a given amp, if you’re interested in the relative sound of a preamp the logical, direct, and more common reviewer methodology would be to compare it to other preamps. Duh.

Hmm. So now we have the claim that:

(a) to hear what a preamp sounds like, try it with many amps and see what qualities persist through the changes.

vs.

(b) to hear what a preamp sounds like, keep the amp the same and then change between preamps to listen for the changes between preamps.

I suppose these are not necessarily at odds, though. They could be complementary?

Another option might also include

(c) Keep the preamp and amp the same, and change the tubes in the preamp only. See what qualities persist through tube changes.

I'd guess that (c) offers the least information, but it would offer some, no?

Let’s just call it a complex affair that can reach self interpreted conclusions via many different paths.

And if one had a textbook to explain it all, then it would say much the same, with some routing possibilities given in the text, for reference. Where the one attempting to apply the text is told to have a go at it.

Like driving a car. A thing, or act..which is an in-situ continual correction - that is meandering forward.

If one is trying to set such in stone, that would be fruitless, as it is not universally applicable by any measure.

Everything affects everything so there is no hard set conditionals in any of it.  And, if one makes it to the set conditionals, somehow, the whole thing is individually in parts and in the connected self altering whole (as a unified chain), then we deal with individualism and individual interpretations. 

There most definitely is a lot of hard scientific and engineering and measurement data in all of it, but the self created nature of human hearing as individuals, and the breadth of the variables in hardware and humans... ends up reducing it all to a wine tasting experience.