6C33C-B on 8W

[SVStube]

"High voltage" and "low voltage" (300V 200mA and 200V 300mA) modes have different sounds. You can do experiments, but an output transformer with the ability to change Ra is needed for this.

 

[Francois G]

It is recommended to try to work with a half heater (half cathode), which can reduce the heat generation and the anode characteristics are more linear.

Interesting! What about feeding the series connected heaters, say 10-11 volt? Any experience in this regard would be welcome. Also, could you provide more information about your output transformer? What is the winding ratio for CFB?