This two-microphone amplifier was found in a April 1961 Radio Electronics Magazine. The circuit is powered by battery and has a 600-ohm line output.
This circuit from an 80's publication also features low input capacitance. FET can be a modern...
This old version of analogue switch was found in a 1969 documentation. Components of the time are...
In this circuit the gain decreases as the input signal intensity increases. The circuit is from a...