This midrange filter for sound systems was found in the May 1988 issue of Radio Electronics magazine. The circuit is based on a dual amplifier that must be powered by a symmetrical source.
This circuit can be used as a rhythmic light or as a control shield for incandescent lamps from...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
Settings like this can be found in this section and on this website, but from different sources of...