We all know that classic Marshall gain. Which brand of 12ax7 or ECC83 tubes are you finding very good luck with these days for your Marshall? (Please specify type of Marshall). From what I hear tube quality changes all the time. I have used two amp techs lately - both says he orders and tests all tubes he receives and sends many back. One swears by Ruby and the other by Sovtek. I loved the Ruby sound - thick and lush gain but not gritty. Another tech put in Sovteks and I find them to be tight (no flub -which is good), but that also seems to mean but too gritty when over-driven. I have a chance to buy a Yamaha T-50 (based on a Soldano design) - I already know about the design drawbacks of these amps (choke, reverb, caps), but it comes with all-original Japanese ECC83s and "winged" 6L6 power tubes. I am tempted to buy it for the tubes alone. Where are you finding the best quality pre-amp tubes these days?