ABSTRACT
Th e preamp and distortion circuits in the previous chapter are useful on their own to boost a low level signal or make an electric guitar sound legitimate but also in conjunction with other circuits. An ordinary line-level audio signal (such as the output of a CD player) measures a bit less that 1 volt peak-to-peak, and fl uctuates in a curvy, Baroque way; the circuits we’ve been making with CMOS digital chips put out 9 volts peak-to-peak (if powered by a 9-volt battery) and snap between 0 and 9 volts with Modernist decisiveness. But with enough gain and distortion, any analog audio starts to look like one of our digital square waves. Th e more it looks like a digital signal, the easier it is to fool other digital circuitry into accepting it as kith and kin. Th is deception lets us easily interface sounds from the analog real world to our digital circuits for unusual signal processing.
