What FET to choose for HV source follower

[Koektrommel]

Dear all,

I started to design a FET source follower circuit which I want to connect between my preamp and power stage circuit. I will most likely use a Constant Current Source between the source and ground.

Some characteristics:
- Signal swing: 25 Vp-p
- Offset voltage: 100 V DC
- Supply voltage: 300 - 500 V DC
- Bias current: 5 - 25 mA

Which characteristics should I keep in mind for best audio performance? Any recommendations?

Thanks in advance,
Jos