Wiring head unit to the battery...

[9deuce9rr]

Sorry for such a noobie question, but I just want to make sure I do this right.

A couple months ago, I had a spare head unit I attempted to wire it in just to have some music while working on the car. However, when i connected it to the battery, it blew a capacitor.

I have replaced the capacitor, but was wondering if there is usually a resistor between the battery and the head unit to reduce the current going into it? I want to be sure this does not happen to my new head unit when it goes in.

TIA