How to protect audio device in car amplifier
Load dumping... be prepared: -



Maxim say: -


  The most aggressive of these surges is the so-called "load-dump pulse"
  (Figure 1). This transient occurs when the engine is running and the
  battery lead is disconnected, due to a poor connection or accidentally
  while the alternator is charging the battery. The magnitude of that
  transient depends on the alternator's rotational speed and field
  excitation at the moment of disconnection. The surge can last several
  hundred milliseconds and reach levels of over 100V, which is
  potentially lethal to semiconductor circuits.


Do you need to take care of this potential problem? It's up to you. Here's the article.

It offers a few ideas about what to do to protect against load dumps such as the circuit below (obviously using a maxim device): -



So, protect at source and if this can't be done protect as close to the source as possible and if that means the two wires feeding your amp then so be it.