Found in an Electronics World of 1966, this circuit makes use of FETs of the time. Modern equivalents can be used. The high voltage supply suggests its use with tube amplifiers.
This variable power supply circuit was found in a German publication from the 1980s. The circuit is...
This circuit is suggested by Texas Instruments and is based on a relaxation oscillator with...
In the figure we have a typical Wien Bridge oscillator with AGC. The negative waveform is sampled by...