I collect direct heating triodes for fun and later found they are very good for single end audio power amplifiers.
The concept is simple, I use independent power supplies:
1. 0-1200V 450ma DC variable to fit power tube (high voltage dangerous)
2. 0-450V DC variable to fit voltage amplifier tube
3. 0-100V DC variable for grid fixed bias.
4. 0-12V DC 15A x2 filament supply
Power supply tower with military grade high voltage filter capacitor bank (see pictures below).
Easily change the tube socket arrangement that fits different input-output tubes and stage block module board covered with studs for point to point wiring so that circuit modification or component change becomes easy (see pictures below).
The output tube connection is simple but different tube will give a different sound. The voltage amplifier arrangement has many choice such as SRPP, Cathode follower Direct couple, RC couple or transformer couple. I will try them one by one to see the results.
Thank you for visiting!