Ok, so after talking with lord valve, and looking at different sites trying to figure out which preamp require a modded power amp, I'd like to have a concise list available. I don't know if a thread has already been done, but let me ask you guys anyways, and if you can point me in the right direction, that would be super cool. The question is, which of these preamp have a relatively low output signal that may require an extra boost for a power amp? Ampeg Svp Aguilar 659 Raven Labs universal instrument preamp (do they have a bass only preamp?) Swr IOD and grand prix Eden navigator Demeter vtbp 201s and hbp -1 Also, feel free to add other preamps, with the answer to the question, and also feel free to elaborate if you dig the sound of them. If you are wondering what kind of I sound I would be into, I need to go from smooth Jazz, funk and slap to out of control heavy rock and metal. I have tried 4 or 5 of the ones listed above, and they all were nice sounds.