I have learned a lot and I have the last years wanted to build a constant current draw gnd cathode amp x2 with passive RIAA filter in between. It should also have CCS made with SS and LED. The simulation looks like the picture below. Everyone who reads John Broskies blog at Tubecad should be familiar with this design.
The last few years Johns Aikido circuit have had a great attention everywhere. It's to easy though. I would like to have done at least some of my own testings before I go ahead and just build something readymade.
I'm right now thinking of a combination with the above circuit and the latest diffpairstage John suggests. The unicorn amp which have a little of the above and a little Aikido touch. Injecting PSU ripple to get rid of it at the output.
It took me some time but finally I took the short turn and bought the new card (2009) from John Broskie and Tubecad. The Tetra One all tube and also PSU on the same board. It uses the CCD concept and, well, the layout for the amp was ready to just populate with my NOS Telefunken tubes laying in boxes for years, waiting for the moment to be used. At last.
Maybe I will try the above scheme with the CCS in the future. But I have also learned that the time you share with your near and dear, work and other activities is pretty limited. I will never live that long to try all I want. Life is a bit short. One can only hope to be of good health some more DIY Audio years to come.
Project not yet finished ... but.. There is a RIAA amplifier test I have managed to do and in a way document some of my work. Read about the RIAA amplifier test here.