Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This MOSFET circuit for microphone applications was found in the December 1969 issue of Radio...
This operational amplifier circuit with power output using complementary transistors was found in a...
This circuit is from a publication of the 70s, but it can be easily assembled with the BC548. The...