Reinhard, you are obviously a pro. I am not not sure where the Jfet is located. I would try to upload a picture and perhaps you can point me to the right component?
Don`t get me wrong. Hovland uses a single Fet working on a resistor. My Output stage is a J-fet working on a current source with a higher bias current. Ther are numerous new parts and an updated power supply. Hard won knowledge and nothing to report here.