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.
This non-inverting AC amplifier was found in the February 1990 issue of Radio Electronics...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
This amplifier, common in 1986, uses a hybrid integrated circuit that can offer some difficulty to obtain...