Jfet's make much poorer and less predictable current sources than bipolar transistors. To quote from Horowitz: "It is important to realize that a good bipolar transistor current source will give far better predictability and stability than a JFET current source" .
They are fine for audio circuits and the value of current can be tuned by selecting the right source resistor. They can be simpler and made as a two terminal devices which is not easy for a BJT current source. Oh yeah.... they sound better. Keep in mind that Howowitz comes from an instrumention backgrund where precision is much more important than in most audio applications.
The idea is to feed LM431 shunt regulators for several supplies.
I've read that feeding them with a current source has some sonic benefit above just a series resistor (at least for analog supplies).
Another reason I want to use a 2 terminal CCS is, I sometimes use unregulated supplies; so using resistors they turn out big and the LM431 might be overloaded when coping with voltage
For larger currents, say 50mA at Vds=10~15V one jfet can't handle all the power, so I want to parallel two jfets...
Any suggestions for types ? I think one needs jfets with low "goss". Are the J111/112 good candidates for idds 20 and up ?