I substituted a TC072 low noise in place of the JRC4580 that they ask for in a "Pastie Drive"
http://home.comcast.net/~gprause/BuildDocs/Pastie_V1.1_Build_Doc%20V2.pdf
The J201s both measure 9.02 Gate, 470 Source, and 2.98 Drain. I am getting some squealing when I dime the grain and Tone Only when the Mid switch is Down completely. I also noticed that I get some feedback if I am facing the pedal with the Guitar again only when the mid switch is down.
I have some JRC4580s coming in, but I am wondering if there is something else causing the issues?
The tl072 should work just fine. You should be getting 9v at the drain of Q1 and Q2.
Sorry it is 9v on the drain. I had my numbers backwards. I tried other j201s and 2n5457s but I get the same issue. I am going to go back and check the soldering and do an audio probe tonight.