BIOLOGICAL AMPLIFIERS 



Input +300^v^^^^ 



Output 



^70k<>56k All valves EF 50 

 orSPei 



Figure 39.22 



220 k 



Input 



< High gain 



static balance 

 or'Y shift' 



100 k 



Gain 

 control 



330 k 



V2ECC83 



150k 



Output 



V2ECC83 



+ 300 



Figure 39.23 



634 



