Somethin' don't look right

[jeff]

Does this look right? I'm building a tube wah and before I blow it up I thought I'd ask. The cathode resistor(R10) is 1K8. Seems kinda small to me. I don't know much about cath followers, please help. Most schematics I've seen have a 100K.

1K8 just stuck out to me as low, and thought I'd ask before I plugged it in.

 Here's the original with MOSFET http://www.geofex.com/Article_Folders/tube-wah/tube-wah.htm
 In it he says"[using the mosfet] lets you save one half-tube; in this case, there would be a whole additional tube needed. You could use a cathode follower if you like. The exact circuit will work."

Should I take "The exact circuit will work" to mean use the same values but use a tube in stead of the mosfet? His resistor is a 10K not 1K8 but everything else looks the same.

I'd like to use a tube just because I have it on hand.

[Matty_V]

Take my help with a grain of salt cause I'm not an expert. I'm not sure if 1K8 is the correct value for R10, but R8 is the 100K you're speaking of because its dc coupled to the previous stage. The grid of the second cathode follower will be at much lower potential so it doesn't need the 100K cathode resistor (not sure what kind of coupling you would call that??). Somebody else chime in, cause I'm still learning too.

[jeff]

I came across this

"But I'll tell you how to do it. Remove the MOSFET. Connect the plate of a triode where the MOSFET drain was. Connect the grid of the tube where the gate was. Connect the cathode of the tube where the source was. Change the source resistor from 10K[1.8K in brown schematic(R10)] up to between 51K and 82K. Done. The tube will not provide as clean a feedback drive. It's really very much like the source follower after the plate of the first tube, but with only one source resistor."