I need a little bit of advice with my Alembic preamp. I just bought this guy used and I decided to change the tubes since #1 They seemed to be crackling and humming and #2 they shoot out a LOT of gain! I decided after doing some research that a 12AU7 might be a more polite sounding tube for my pre, so I bought one and put it in last week. It sounds really good and the gain is now at a level out of the pre that I can deal with. I now have the idea of running a 12AX7WA that I just bought in the other channel and running the 12AU7 in the other. Is there a problem with this since they both run off the some power supply? Is there any need to do a bias adjustment and is the pot on the circuit board for bias adjusting or is it for something else? The concept I'm thinking of here is to have a two channel pre with two different settings or even cascade one into the other and get some cool overdrive sounds that are tamer than cascading two 12AX7's. Am I out to lunch with this or is it even useful to do? I do like the 12AU7 already and I've heard others complaining of the gobs of level that this pre spits out. The 12AU7 only provides 20X gain compared to 100X gain in the 12AX7 so it is better when level is an issue.