Using transistors at the time, this circuit was found in a 1970s documentation. Transistors support modern equivalents for 2A currents at least in the case of the output transistors.
This circuit can serve as a basis for a digital mixer or simply for a noiseless switch of audio...
This traditional mixer configuration with a high input impedance was found in a 90’s Popular...
This medium wave radio works with any general purpose NPN transistor. The diode must be made of...