This amplifier stage without an output transformer was found in Radio Electronics magazine from October 1963. The supply is 12 V, and the output is 8 or 16 ohms.
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....