I love preamp pedals.
I think the favorite I’ve built was the BE-OD clone, Thermionic distortion I think it’s called here. I guess it’s more of a distortion pedal but I think it works well into a power amp, as long as you’ve got an effective presence knob. Otherwise, just sticking a graphic EQ pedal after it works great to get the voicing right. Takes boost pedals like a champ, great feel for high gain.
there’s also a triple-wreck clone pcb here, I forget what that one is called. I can’t remember much about that one apart from it being a bit lacklustre compared to the thermionic distortion. I gave it to a friend a while back.
the VH4 pedal has a cool voicing but is more ‘rock’ sounding, not my first choice for a tight metal sound.
I’ve wanted to build one of the dr boogie preamps for a long while. I had planned to do a veroboard one but never got around to it.
apart from the Thermionic distortion, my favorite preamp pedals have actually been the AMT legend preamps, but I didn’t build those. I have the R2 which really nails the Mesa recto kind of sound, and the K2 which is a bit brighter/tighter/clearer and a bit more Marshall sounding. They both take boosts very well but if you push too much volume they get kinda ‘splatty’ sounding. Only really a problem when I tried using the integral preamp with the volume on 10 as a boost, tubescreamers are fine. They both have tons of gain on tap so not really a problem anyway.