Found in a 90s Radio Electronics, this circuit uses a ceramic capacitor (C1) as a sensor. The operational amplifier is a double 741 of the time.
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...