The amp (or amplifier for its full title), is a key part in a vehicle’s sound system and as the name suggests, it’s job is to amplify low level audio signals so that they can be used by the speakers to generate sound.
There are two types of amplifier and their quality differs considerably. The first type is a basic factory amplifier which is built in to the car audio head unit, which is used to power a small number of speakers. The other is called an outboard amplifier. This amp is separate to the car audio head unit and is capable of providing a much better sound and power more speakers than the head unit amplifier.
Signs that the amp is faulty would result in either no sound or poor sound quality. This could include hissing, cracking or background noise coming through the speakers. This could be a wiring issue, or could be something more specific to the amp. Other damage to the amp can be caused by the amp overheating. This can be rectified by increasing the airflow to the amp. An unblocked fan should always be present.