This 4-channel mixer amplifier was found in an American publication from 1947. The circuit uses counterphase output tubes and a transformer power source.
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...