This circuit with RIAA equalization is from 1985 US documentation. The circuit has a flat response of 150 Hz to 40 kHz. The power supply must be symmetrical.
This traditional doubler configuration with the 555 IC can be found in other articles on the...
This circuit is from an 80's component manual. The components are from the time, but the circuit...
This circuit for the 3.5 MHz band (80 meters) was found in an old radio amateur documentation. The circuit...