Judging by what I've seen, almost every pedal effect that includes a tube on its circuit is actually an overdrive or even a distortion pedal. Now, I wonder if there's any tube pedal that acts not like an overdriver or distortion pedal, but like a preamp that adds some "tube flavour" to a solid-state amp. I saw some pedals that come close to this, but all of them finally get into overdrive territory, and that's not the goal. I'm talking about pedals, but it also could be an off-board preamp unit, of course. Any recommendations? Maybe some schematics? Thank you very much, best regrads.