While the original Starving Student was an incredibly high value for money amp, it is fair to say that since disappearance of 19J6 and the standard tube becoming the 12AU7 it has lost some of it's bang for buck, with most 12AU7s costing well over $10 for a decent tube. Since building my Starving Student with CCSs on the tubes and a pair of linear regulated PSs (~48V for the plates and 24V for the MOSFETs (powering the tube heaters of course)) I've been trying to think of ways to shrink the amp and increase its performance while still retaining a lot of the characteristics of the amp such as the single MOSFET per channel providing current gain but while removing the blocking cap on the output which significantly modifies the amps dynamics.
Obviously these sorts of changes require the addition of a fair number of components, and there is the obvious fact that if the output capacitor is removed then the tube heaters can no longer act as current sinks to bias the FETs into class A. If the tube heaters are no longer needed for this purpose then there is very little reason why one couldn't only use 1 valve for the entire amp with one triode per channel. Given the cost of these valves, the extra $10-$15 gained can go a long way in transistors, regulators etc. to get this amp running without a blocking capacitor on the output and a CCS on the tube.
Below is my current schematic, B+ is provisionally 60V to be provided through a a couple of PI filters and the bipolar supply for the output will be either +-12V or +-15V:
The load on the MOSFET is similar to that which is used in the SOHA II (as is the servo, although they're just very standard).
I don't yet know if it's best to take a page from the SOHA IIs book and pull the cathode negative while attaching the CCS to the tail of the valve. This is the area I'd like to for help in, as I don't really have any experience of these sorts of modifications.
This design was the reason why I requested a various complementary mosfet buffer designs, but of course class A does seem like a nice and pure output stage in keeping with the original design.
Any comments on the design would be welcome so that I can avoid any really foolish mistakes,