Before I've got it by a very low price but its style is luxurious ST tube, named "19". It is 1930's direct heated twin triode and I guess it is not so popular for audio maniacs (guessing from its price.)

Its datasheet says "class B twin amplifier" not "vacuum tube" or "direct heated twin triode" and the purpose of this tube was strictly specified for "push-pull".

So I quickly made push-pull power amplifier by just three components, tube and input and output transformers. Each of trans was just available one and this amp does not have any clever design, just connecting! (as the data sheet says, this tube may be class-B amplifier by its nature..)

Actual operation can be found in the following movie. Indeed, its sound is very nice!!