I have a 1990 DRRI I picked up recently and it came to me completely stock. It doesn't have a mark on it and I suspect it hasn't seen much action. Anyway, I did replace the original power tubes with some Tung Sol RI's and bias the amp, and replaced the reverb tube with NOS JAN 12ayz. The power tubes were labeled with Fender, Groove Tubes, and Electro Harmonix. I think the pre amp tubes are groove tubes. So I was going to swap some tubes on the pre amp side and see what sounds the best. I do have a couple old stock 12ax7's. A Raytheon black plate and what I think is a Fender branded RCA. Then I also have a slew of CP 12ax7's to try too. Any experience you guys can share before I start would be great. Oh, I should mention that the amp sounds great but gets a touch raspy at volume. This may be the speaker but I wonder if a tube swap might help?