Fetzer Valve Revisited without the R-Source trimpot

[mordechai]

I have a PCB that can accommodate the Fetzer Valve Revisited circuit, but it has space for a fixed resistor rather than the trimpot coming off the source of the JFET.  Can proper biasing be achieved with just a fixed resistor in that position?

[slacker]

Yes, just use their calculator to work out what value that resistor should be.

[mordechai]

Thanks...great tool. 

For the "average" J201 reading, with the Rs at 1076...I am assuming that a 1K fixed resistor would be the best choice, yes?  If that's the case but it's still just a bit off from 1076, can the Rd trimpot compensate sufficiently to obtain the right bias?

[esdiezy28]

I think it really will depend on the characteristics of each J201. I've never used the trimpot method. In my 9V builds with a J201 I used a 10k Rd, and 1k Rs. 3 out of 4 times it worked flawlessly. Had to take one build apart, ended up using that J201 for a buffer in something else.