ABSTRACT

In the contrarian spirit of hacking, the fi rst circuit we build from scratch is based on the misuse of an Integrated Circuit (IC) never intended for making sound. Th e “Hex Schmitt Trigger” is a CMOS digital logic building block consisting of six identical “inverters.” An inverter takes a logical input, 1 or 0, and puts out its opposite (so 1 becomes 0, 0 becomes 1). Th is particular version of the inverter is useful to us because it runs for a long time on a 9-volt battery, it is very cheap, and it contains a circuit element known as a “Schmitt Trigger” whose fi ne points you don’t need to understand at this point but, trust me, transforms the chip from a simple digital no-man (as opposed to a yes-man) into a versatile sound generator.