R.O.G. Thor (jfet bias question)

[nepalnt21]

so i just completed breadboarding "thor" by runoffgroove, http://runoffgroove.com/thor.png and it sounds pretty derned sweet ...

(tangent , i need a new 9v battery cause i stupidly stuck a jumper from ground to positive, and didnt notice for like 30 seconds  )

but anyway, i had to change out the 20k trimmer on the drain of Q2 (had to go all the way up to a 1Meg-ohm) in order to get that voltage to 4.5V... what gives? is this anyone else's experience?

(if you hadn't guessed, i'm still a bit wet behind the ears when it comes to this stuff)

thanks for any help

[Jeema]

Well, JFETs typically do have a wide manufacturing variance, but there might be something wrong if the circuit specifies a 20K trimmer.

I would check to make sure you actually used a 1K resistor at the source of Q2 and not a 10K or 100K or something...

[PRR]

> had to go all the way up to a 1Meg-ohm

Almost certainly the Source pin is not 1K to ground as it should be.

Possible other-flaw is the coupling cap to the gain-pot to Q2 Gate leaking or shorted; or no ground on gate network.

[nepalnt21]

 

yep, it was a 100k. thanks lol!!!