This amplifier with fixed AC bias was found in a 1947 documentation. The circuit uses two transformers in the power supply and two full-wave rectifier tubes.
This circuit is from the 1994 Linear Applications Handbook. The operational circuit can be...
This circuit is suggested by National Semiconductor (now Texas) in an old manual. The circuit...
With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a...