Found in a 1968 American documentation, this circuit uses an operational amplifier that is uncommon today. The feed must be symmetrical. The gain is 40 dB.
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...