This circuit was found in a British documentation from 1969. It can be implemented with modern transistors. The pass band is 6 MHz.
This circuit was found in an American publication from the 50's. The transistors are made of...
The circuit shown is an amplifier for medium impedance headphones including bass and treble...
This circuit for an optical audio link using LED or LASER was found in a 90s QST magazine. The circuit...