The outputs of a preamp are the electrical jacks that prepare and direct an audio signal from its source toward an amplifier. Engineers build preamps with outputs designed to serve different purposes, such as professional audio recording or high-fidelity playback for a car stereo.
Crutchfield defines preamp outputs as the electrical sockets on the back of a car stereo's CD receiver, while K&K Sound defines the preamp output in relationship to a pickup or microphone as an audio source. In both cases, the preamp serves to do any of four things to an audio signal: boost its intensity, improve its signal-to-noise ratio, adjust its tonal characteristics or blend it with another source signal. The output of the preamp delivers the prepared signal to an amplifier, which then routes the signal to one or more loudspeakers.
In high-fidelity stereo systems, such as those used for cars, a preamp can contain multiple outputs. This allows the preamp to prepare a single audio single for playback through more than one amplifier. Some car stereos feature a set of nonfading preamp outputs. Nonfading preamps allow sub woofers to maintain consistent volume even when the user fades between the volumes of the front and back speakers.