The following is excerpted from an email exchange about the K2-YJ. This particular snippet comments on the merits of current feedback from the output follower triode plate to the previous stage via R4, R5 and R14. Bob and I wondered why Bruce Seddon, who designed the K2-YJ did not simply strap R4-R5 to a portion of R1, and avoid the large voltage drops on R4 and R5.
-Joe Sousa, Webmaster (added 8-30-8)
The K2-YJ was one of MY favorite amplifiers, TOO, but why the hell did he take the positive feedback from the plate of the output stage ( to sense the output current) and then level
change to -260 volts? Why didn't he just feed it over to a tap on the plate resistor of the differential stage? I tried that, and it worked beautifully. I modified my K2-YJ. It worked OK both ways, but better with my scheme. Further, those level-changing
components could hurt the input dc Vos error if they drifted.
I asked Bruce about a year ago and never got any reply. I guess he was going down hill and could not remember why he did it. / Sigh. / rap