This circuit is from an old Japanese publication of 1962. The circuit uses two batteries, one for the filaments of the tubes and the other one of high voltage for the plate circuits.
The presented circuit was found in the National Semiconductor FET Databook. The setting applies to other...
This configuration with the LM383 appears elsewhere on this site. The circuit shown was obtained...
This very high input impedance preamplifier is from a publication of 1977 but can also be mounted...