been working on this one a while, with all the popular transistors disappearing, I 
hope that this one won't go obsolete before the boards are out. I don't think so 
because Fairchild has said that the bc parts should be available for at least 5 years 
but onsemi said the same thing. 
  
This one is a diamond transistor input set, used as a voltage to current converter. 
A pair of Wilson current mirrors with input and output cascade as the VAS 
  
and a triple darlington output stage. 
  
http://gilmore.chem.northwestern.edu/cfa2.pdf 
  
if someone knows of better surface mount parts to replace the bc series, I might 
as well do that from the start.  ft >150mhz, hfe >100 Vceo >50 etc