Learn Audio Electronics with Arduino

Chapter 6

AC circuits

Chapter 3 looked at direct current (DC) circuit theory, where the voltage and current levels in a circuit do not change over time. This chapter introduces AC circuit theory using the sine wave, which is the fundamental component of all pitched sounds in an audio signal. The chapter begins by introducing the fundamental elements of a sine wave – amplitude, frequency and phase (though an in-depth discussion of phase is outwith the scope of this book). The most common time-varying component in electronics is the capacitor, which stores charge over time. Capacitance is defined in terms of charge and voltage, with the charging time being dictated by the time constant within an RC series circuit. Capacitors change their reactance ...