Battery powered DC90 line or 300 Ohm headphone output stage further comments

 At your risk. Dangerous voltage. Take all safety precautions.

Referring to:

https://euroelectron.blogspot.com/2025/04/battery-powered-electron-tube-line-or.html

What if all RC is removed from anode and transformer directly connected to anode as on single ended class A power amplifiers?

It worked fine with DC90 grid at space potential and Vb=48V. Huge sound, too loud (protect your ears). Anode current becomes of the order of 1.6mA.

Only serious problem is that the transformer will saturate with DC current. A sense of stain was apparent. A transformer with air gap must be used.

Since the sound was so big anyway Vb+38V would be enough in this topology giving about 0.7mA anode current. So it is neat as ordinary 9V batteries, 4 of them can be used is series as a very clean power supply, making for example a world class headphone amplifier.