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.
Found in Popular Electronics from the 1980s, this circuit can use more modern transistors such as...
This circuit is from a Radio Electronics from February 1970. The integrated circuit is an...
This is stage is transformer coupled and was found in na old publication of the year 1958. The...