I apologize in advance for the noob questions, but I just stepped up from a Class 5 and I can't find any of this info on the new DSLs. I kind of need a quick lesson. I'm not a total idiot about this, but I don't want to take any chances. I was just about to roll a couple of NOS preamp tubes in V1 & 2 in my new dsl40c when it dawned on me that I don't know what all these tubes are for and if I might screw something up if I put a wrong tube type in the wrong position. It's my first amp with more than 3 pres. Can anyone give me a rundown of what the preamps are? I assume V1 is closest to the input like any other amp? What are V3 and V4? I also assume V4 is the PI?...or am I way off? It also just occurred to me that I probably have to re bias if I swap power tubes???? Any info at all in this department is much appreciated! edit: I have some pix, but I can't download them to my computer at home, I'll post them if I need to in the am.