A capacitor will give you more stable voltage at the audio amplifier level. However, keep in mind that a capacitor is less than 100% efficient, so it will stress more your electrical system.
Lights dimming at high volume means probably that the battery is weak, or the wires are oxidized. Try cleaning all connectors, and if the lights will dim, then change the wires.
Calin
Lights dimming at high volume means probably that the battery is weak, or the wires are oxidized. Try cleaning all connectors, and if the lights will dim, then change the wires.
Calin