I have poured over alot of the posts concerning this question(I have a screen generated headache ) and found the general consensus that the change over to 12ax7's from 12dw7's happened during the MTI era thus changing the tone from the earlier years. Yet my MTI has the tube guide sticker over the plug in holes that is marked from left to right 6c4,12dw7,12dw7,12ax7a and 12dw7. They are all GE's and one sylvania(yeah!) Were these MTI's just a hodge podge of leftover parts from Magnavox? Another person said I would probably find Plastic posts on the pots but when I removed the knobs they were metal. Was this era scatter shot without conformity in production? I can't see the japanese doing that. Oh yeah, It sounds AWESOME too!!!