oh ya and what happens if you dont upgrade ur alternator? and how much does it cost? and how much would be a rediculouse amount? (500amp alternator as an exsample)
A capacitor is wired into your power wire before the amp. When your amp needs a large amount of power at once, your capacitor will discharge so the amp will get what it needs. It makes sure your voltage doesn't sag. Although if you have a capable alt, you really shouldn't have to worry much about that anyway.