[Bret L]

Morons just can't quite grasp the concept here. The 6S33 is not a
poor audio tube just because it was not originally designed for audio.
It's a poor audio tube because of its characteristics, including those
not selected for in plant testing. It is only tested in ways relevant
to its operation in the military gear for which it is designed. The
wild variations in mu, plate resistance, and filament characteristics
(there is one plate, two separate filaments, the tube was designed for
a specific regulator circuit) as well as gassiness are tolerable there
but not in the audio circuits.

Is it possible that a particular amp using these tubes might be
pretty good? Sure. Is it a good idea to choose this tube? No.

It's like my Carolina Hauler truck. The school bus transmission and
rear end are way oversize for general use. The factory did not build
them that way for good reason. Mine works for me but it isn't really a
daily driver.