A combination preamp/amplifier, typically for two-channel stereo. The preamp provides the input switching, and the amplifier boosts the signals to the speakers. Integrated amplifiers are widely used and may be combined with a CD player in the same unit. If the speakers are also built in, the device is often called a "boom box," or for higher-quality products a "music system," the latter popularized by the widely advertised Bose Wave and Bose Acoustic Wave tabletop systems. Contrast with component audio. See preamp and boom box.