A/V What?
An A/V receiver combines three audio components in one box. Primarily, it performs the traditional roles of a preamplifier and power amplifier. The sound for any home theater begins as a relatively low-level audio signal coming off a source component such as a cable box or disc player. These days, it’s more likely to be a digital audio signal than an analog signal. That signal gets converted between digital and analog as needed, manipulated to affect your volume adjustment, and might perhaps have some bass and treble contouring (or more sophisticated equalization) applied before it’s sent to the power amplifier, whose only job is to pump it up to the power level necessary to drive your speakers to sufficient volume.