The IXCP10M45S is sold as a current regulator so the usual mosfet parameters are not shown in its datasheet. It could be a normal depletion mosfet but I wouldn't take the risk of using it as a follower. It cannot be used as a CCS in the PSU, the current to feed the zener is 1.7mA, and the IXCP10M45S has a minimum of 2mA. It could be used as a CCS (10mA) in the follower stage, but I don't know about the result. It would be a $3 saving each. Again, I wouldn't take the risk.
I bought a bunch of 10 IXTP01N100D and selected them for the minimum |Vgs| to use as followers and maximum |Vgs| to use as CCSs.
An STF3LN80K5 (cheap but good) can be used as a follower (also as a voltage regulator in the PSU), but the midpoint will go down around 5/6V because of its positive Vgs. This is only cosmetic, with no impact on the sound.
Before some ask: I tried the DN2535/40, as a CCS, but it seems below a certain current it doesn't work. Some in this forum say its sound is not the best.
I bought a bunch of 10 IXTP01N100D and selected them for the minimum |Vgs| to use as followers and maximum |Vgs| to use as CCSs.
An STF3LN80K5 (cheap but good) can be used as a follower (also as a voltage regulator in the PSU), but the midpoint will go down around 5/6V because of its positive Vgs. This is only cosmetic, with no impact on the sound.
Before some ask: I tried the DN2535/40, as a CCS, but it seems below a certain current it doesn't work. Some in this forum say its sound is not the best.