A head unit is the first step in any car audio system. The head unit reads an audio signal from many sources such as a CD, Auxillary connection, USB, bluetooth, SD card, or others (depending on the specific head unit). Most head units have small built-in amplifiers that can be used to power speakers. Head units also have RCA pre-out connections to send the audio signal to an external amplifier for more power and greater sound quality.
There are two main types of head units, single DIN and double DIN. A single DIN unit is small and fits the stock head unit location for many vehicles. A double DIN is twice the size of a single DIN and often has a large touch screen.
Different head units have different features, including but not limited to:
- Crossovers (High pass, low pass, and/or bandpass filters)
- Equalization, including Auto-Equalization
- Digital to Analog Converter (DAC)
- Time Alignment, including Auto-Time Alignment
- Digital Signal Processing (DSP)
- Multi-color customizable displays
- Remote Control
- Detachable Faceplates