Experimenter 45

This is by Matthew Reidsma in a past issue of Valves magazine. Circuit redrawn here.



Notice how simple the circuit is. The initial circuit calls for a cell of 1.2V but Matthew later revised it to 2.4V. You can budget the B+ at around 380V or more, depending on the DCR of the output transformer. By the way, Matthew used the Hammond 125E at 3k.

The 0D3 or 0A2 can both be used. Any gas regulator will work as long as it gives 150V at the plate. You might prefer the 0D3 over the 0A2 for aesthetics reason.

Note the idea of "tapping" or "recycling" the output tube plate current to drive the input tube is not new here. Refer to similar circuits like Jeremy Epstein's "Free Lunch", "Monkey" and also "Direct Reactance". Do a Google and find out more. 


45? Do you have any idea how expensive this tube is?

Yes, I'm aware of that. You don't have use a 45 here, Can just substitute with a 2A3. Read other pages here to find where you can get good value Sovtek 2A3s. Just be aware that filaments for 2A3s and 45s are different so don't go swapping them here and forth.