This converter that allows high voltages to be obtained from batteries was found in Radio Electronics magazine from June 1959. The circuit uses a special transformer providing 9 to 18W of output.
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...
This rapid response amplifier uses an integrated one that is not common today but can be...
This low noise microphone preamplifier circuit was found in American documentation from the 90s....