Has anybody used this PCB for a preamp? The price is right, and Im just looking for something to go with my 6B4G SET. It looks like a relatively simple build, but Im wondering if the circuit is tried and true? I have a boatload of 6SL7s, so Im wondering what Id have to change in order to use them instead of the 6SN7? It looks like a pretty good PCB. I know some tube purists arent crazy about PCBs, but Im pretty new at this kind of stuff, so Im going with kit-type stuff for now until I understand this stuff more.