A capacitor is an energy storage device. It pulls voltage from the battery and stores it for later use by another device. This is particularly helpful for amplifiers. Long, sustained audio notes require lots of voltage pull that the battery might not be able to supply at times. Therefore, if you wire a capacitor between your battery and amplifier, you will have a store of voltage that the amplifier can draw on to sustain notes.
Disconnect the fuse from the positive terminal of your battery. The fuse will be within 18 inches from your battery in an inline fuse holder on your amp power wire.
Go to your trunk and locate the +12V wire going to your amp.
Cut this wire within 18 inches of where it meets the amp. Ideally, you want your capacitor to be as close to the amp as possible.
Solder the end of the wire that is connected to the battery's positive terminal to your capacitor. To solder, heat up the soldering iron and melt the solder (coil) over the exposed part of the wire until it completely covers the exposed parts. Cover the connection in electrical tape for added protection.
Solder a ground wire to the negative terminal of your capacitor. Connect the other end of this wire to any metal grounding source in your vehicle.
Place a 1k ohm resistor in the slot that the fuse used to be in that you removed in step 1 above. Your capacitor will now be charging.
Use a multimeter on the positive and negative terminals of your capacitor to measure the stored voltage. Keep charging it until it has reached 12V.
Remove the resistor.
Connect the +12V line that is connected to your amp to the positive terminal of the capacitor. Solder it into place.
Cover all of your soldered electrical connections with electrical tape or heated shrink-wrap.
Replace the fuse in your battery.
Ensure that your amp is functioning correctly.
