Tube DIY Asylum: Joelt's 6sn7 zero gain cathode follower by rickl

Has anyone built Joelt's 6sn7 zero gain cathode follower circuit? It uses one half of a 6sn7 per channel to drive an amp. I've built it and currently using it in place of my old KT600 pre.

A friend loaded the curcuit into TubeCAD and suggested the cathode resistors should be lowered from 68k to something around 20k.

I have the following dc voltages on the 6sn7:

1 95 (grid)
2 372 (plate)
3 199 (cathode)
4 91 (grid)
5 372 (plate)
6 199 (cathode)

heaters are at 5.95vac

What do you think? My notes show plate power .5w and 3mA current. The 6sn7 tube spec plate curves seem flat at this. Am I reading this right?

I couldn't get the schematic to display anymore on the link below but the circuit is 100k volume pot into a .1uF to the grid. 1uF from the cathode out. 470k from out to ground. The cathode resistor is a 2k and a 68k tied to ground. Add a 1m resistor between the grid and at the 68k & 2k point. Pretty simple.

I did play with the 2k resistors to dial in equal gain on each channel.

If you do look at the below thread, please ignore the PS flames. I'm more curious in the driver circuit.

Thanks,
rick

original 6sn7 thread (Open in New Window)