What gives tube amps their warm distortion? The preamp tubes or power tubes?

[Feanor]

I have always used transistor amps to play guitar through.
But I'm about to buy my first tube amp.
However, there are all tube amps, hybrid amps that have just a preamp tube, and hybrid amps that just have power tubes, and it's kinda confusing. I want to get the sound of an overdriven tube amp, but which tubes give you that, the preamp tubes or the power tubes?

Others might jump in here, but I'll say what I know.

First, do you really want the "overdriven" sound for hi-fi playback. Guitar amps are a different matter because their effect is part of the sound production, but playback back is REproduction.

Single-ended tube amps are popular with some folks because they produce almost entirely 2nd order harmonic distortion which is pleasant to our hearing; the more common push-pull tube amps produce more 3rd order harmonic distortion which is still inoffensive but less so than 2nd order.

OHOH, solid state amps typically employ a lot of negative feedback which creates higher orders of harmonic distortion but less distortion overall. Despite typically lower distortion overall, lots of people are apparently sensitive to even very small amounts of high order distortion and/or they like a lot of 2nd/3rd order -- I'm not sure which.

[Mr Peabody]

Some seem to like tubes in the preamp to give the tube texture and solid state in the power amp for better control and let's face it power is cheaper with solid state. Same reason Hybrids are made. When I had tubes I didn't really get a full effect until having tubes in both pre and power amps.

Another consideration are brands, these days stereotypes are being destroyed, you can find tube amps with nice slam and control as well as solid state with a smooth warm sound. Although I've yet to hear solid state give that same type of presence as tubes.

Also, you can change brands of tubes to look for one closer to your taste, this is called "tube rolling". So once you settle on a component you can then roll in & out different tubes for different sound. In fact, there's a company called Musical Designs who has a tube preamp with 4 different boards to choose from, you can buy the other boards and swap them in and out for a different sound.