While investigating some aspects of charge amplifiers I went back to the roots and had a look at the first patent by Mr. Kistler from 1948 (granted 1950)
The idea came up to rebuild the simple triode CA from fig. 1 and see how it perform. I have a nice collection of tubes, so let's use them
Here the figure from the patent:
and the realized schematic (I used a Telefunken PC92, but used a 12AT7 for simulation)
Pic of the amp:
and in the lab for testing
It worked quite well, here the FRF
There is still some hum and noise and the THD hasn't been investigated.
Well, sand nowadays works better but it was great fun to build.
If I manage to replace my Kepco (beam power tetrode regulated) HV source with a small transportable (universal input) power supply, I will take it to my presentation at the IMEKO XX