Sylvania 336mu

[Electronic M]

Stacked B+ ain't a bad thing and worked well (otherwise it would have been a short lived design), but it is a bit more involved to trouble shoot than a traditional resistor based B+ divider.

[wa2ise]

Originally Posted by Electronic M

Stacked B+ ain't a bad thing and worked well

You're making use of energy (some going to the audio speaker) that would have been wasted as heat in a power resistor. And the audio tube acts a little like a voltage regulator, after some filtering to remove audio.