This simple tone control using two transistors was found in an Electronics Today International of the 90s. Transistors are general purpose NPN types, like the BC549 for greater gain.
This circuit causes an incandescent lamp to flash according to the input audio signal. The SCR...
This circuit is from a factory documentation (National Semiconductor) of the 80's. The power...
The A3906 integrated circuit from Allegro MicroSystems (www.allegro.com) consists of a single...