This circuit was found in a Motorola manual from 1968. As it can be obtained 20 V at 15 kHz from 120 V x 60 Hz. The components are of the time.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...