Using JFETs, this circuit from a 90’s American documentation can generate signals of 0.15 Hz. The JFET can be of any general-purpose type like the BF245 or MPF102.
This circuit with transistors was found in an old Japanese publication, translation of an American...
This 8 W amplifier with germanium transistors was found in a Japanese documentation from 1967. The...
This circuit of the 80's makes use of components of the time. The circuit is from an American...