Experimenter 45

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.





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