I happened to notice a thread on diystompboxes.com started by Aron about Joe Davisson’s JFET Vulcan. You can listen to some mp3 clips that Aron posted in that thread. I had a layout for the BJT Vulcan from several years back so I decided to update it and convert it to the JFET version. This layout has not been verified yet, but I am confident that it is correct. If you do verify it, please let me know. You should be able to fit it into a Hammond 1590B enclosure.
Note that no power supply filter is included. Depending on your power source, you may want to add one. And the output comes from the middle lug of the LEVEL pot.
You may want to breadboard your build first in order to get the bias right for the JFETs. Choose values for the three 100K resistors that give you JFET drain voltages of 4.5V to 5V. Also, check out Joe’s notes about component values for higher gain.