This tone control was obtained in a Signetics documentation of the 90s. The integrated circuit can be practically any operational amplifier. The power supply is symmetrical.
We found this circuit in a documentation from the 50s. It is based on CK722 germanium transistors. The...
Found in an English publication from the 1960s, this circuit uses period components, including the...
This oscillator can generate 2 to 10 MHz signals and was found in an American 1980s documentation. The...