All, I just scored a (199?) TGA-3 combo SN: 138 that was converted to a head. I have always wanted one of these!!!!! I would like to know what types of tubes are you using at the moment..... This one has JJ El34's and six Tung-Sol 12AX7's. I have some NOS preamp tubes, but just wanted some information on what you think would be best for this head. Are you liking 6550's, 5881's or EL34's? NOS or not? Also, does anyone have a tube diagram handy? Which one is the PI slot? I have some really nice late-nineties Sovtek 12AX7LPS tubes for that slot.... Any other info. about this amp would be helpful... Any tips are welcomed!!! One more thing.... What are your serial numbers, and year your Demeter TGA-3 was made? I talked to Jim and he said this one was probably made in the late-nineties, but he wasn't for sure on that.... Just trying to gauge when mine was made! Thanks for your time!