It was the JJ/Tesla 12AX7's that were funky for a while and then I noticed a lot of GT 12AX7M's were tripping-out (non-op to spec) too...friends had noticed it too. But these are amazing-sounding tubes when operating correctly. I must have experienced a bad batch or two there. I am using old RFT's that are doing the job nicely. I have all JJ/Tesla 12AX7's and GZ34 in my Super .38 and they hold-up to everything just short of a beating. I have NOS Tung Sol (RCA) 6973's in there too.