Stabilize the power of tube filament

Stable tube filament heating power = stable emission of the cathode, regardless of the supply voltage or the aging of the tube. Allows you to stabilize the parameters of the tube throughout its life (and not a smooth degradation as with the standard powering of tube filament). Also limits the starting power of the filament (with cold filament), which prolongs the life of the tube.

The starting power of the filament (with cold filament) is equal to half the nominal.

"Directly or indirectly, all questions connected with this subject must come for decision to the ear, as the organ of hearing; and from it there can be no appeal" J.W.S. Rayleigh