This 4-tube amplifier with 6W of output was found in an American manual from 1947. The sound quality is excellent.
This circuit was found in a Popular Electronics from the 90s. The power source must be symmetrical...
In the figure we have a circuit to excite a piezoelectric capsule taking advantage of its resonant...
The circuits below were found in amarican publication of the year 1958. The transistors are...