Here is the simple FET distortion layout for through hole components. The schematic has minor changes to match this layout. So get this new schematic also. The layout is done with the expresspcb design tool. You can download their free CAD tool online. the layout can easily be modified or just ordered through expresspcb (lowest cost small quantity option is for 3 boards in three days for $60.00). The board is small and designed to easily fit in a 1590B box. I will add a parts list shortly.

Go to this link for .pcb file:

use slow download speed(free)

http://www.fileswap.com/dl/pPTjbxAOm/

new schematic:

https://circuitsaladdotcom.files.wordpress.com/2012/10/fet-overdrive_throughhole.gif