This is a schematic for the Mosfet amp. Following are the comments of the creator David Morning , back in 1991 when he sent it to the future homeboy of the Stammtisch Beau Fleuve.
Any errors here are the homeboy's fault.
The 2SJ4X is cross referenced as IRF923X range. I'd suggest IRF9231 as the equivalent. So the drain and source connections are swapped over. The bipolars are much more straight forward. If it is intended to use the amp for an electric guitar, the RC network C7, R15 MUST be removed.