Single stage differential triode amplifier using the 6C45pi.
My version of El Spuddo after (genetic) engineering a Lone Star hybrid with Bill Jaensch and Peter Fowler. It was a long evolution through single ended, constant current source, and voltage regulated jungle which led me to the meadow of "natural motion". There must have been twenty versions of this with inumerable operating points. The 1mm plate of these bullet proof tubes glowed cherry red on more than one occasion and still lasted four years with 12 hours of use daily. One can see why they were used in the Mig 21 Fishbed radar with supersonic penitration and cannon shock wavs to contend with. I was thrilled to have discovered an original topology until I saw another schematic just like it. Some may recognise the similarity to another manufacturers line stage.
There is no dc at all across the transformer primary and with a single ac loop (full differential) the tubes do not have to be matched. This is a good thing because with 1mm plates there are large variations from tube to tube.
AZZOLINA AUDIO SOUND MATTERS