From: user@example.net   
      
   The 6AC10 tube is kind of like 3 12AT7s in the same package, pretty sure   
   everyone has one of those in their junk box..   
      
   But the transconductance of a triode is wussy, so adding a couple low   
   voltage transistors makes a better regulator than you could get with   
   tubes alone. The PSRR is not too shabby for the parts count, better than   
   you could do with the two other triodes in a traditional diff pair and   
   then you'd want a current source for the pair and bla bla bla.   
      
      
      
   You could use an 0B2 for the Zener for that real vintage feel. And if   
   you stick the optocoupler and transistors underneath the compactron (it   
   gets toasty) your regulator is now also "thermally compensated"!   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)