Car audio equipment is designed to work on 12 Volts DC as opposed to 240 Volts provided here in Kenya or 120 Volts in other countries. An alternative is to use a 12 Volts adapter but many of the adapters found in the market provide only 1 Amp or less which is much less than what is required. So the alternative is to use a higher amperage transformer built with a bridge rectifier and smoothening capacitors. But transformers apart from being heavy, produce too much heat and if you overload them then you damage them. You cannot also use a laptop adapter as most have 19 Volts output.
The best alternative is to use a computer power supply. A computer power supply unit provides much more power and if you overload it, then it automatically shuts itself down. A normal power supply can provide 12 volts at 19 Amperes (figure quoted from a HP dc5100 MT Computer) which is exactly what most Car Audio amplifiers need. The yellow cable from a computer power supply usually provides the 12 Volts. I will not delve much as to how to use a computer power supply on an amplifier but give you some very important precautions to watch out for. I strictly do not recommend you opening the unit up if you are not a trained and qualified technician.
First of all use a 3 cable cord, as you have noticed these units are covered with bare metal. As with any other exposed appliance with easily accessible metal parts, you should use a 3 pin cord plugged into a wall outlet with an effective earth connection. This will prevent the metal surface from being “live” if a fault occurs in the unit by draining the voltage to ground. In doing so the fuse will blow and this will prevents you from getting a fatal shock in case a fault happens and you were touching the unit.
If you are not able to plug it directly to the wall socket outlet, then use a fused extension with an effective earth connection.
With the help of a local qualified technician, solder two thick cables directly from the inside of the PSU unit. The qualified technician will know exactly where to tap the 12 Volts from. These are the cables used to provide power directly to the amplifier. Extending the thin yellow cables poses a fire threat if the amplifier demands more current. This demand makes the cables become hot and this is a fire hazard.
The technician will also help you tap the two wires normally used to turn on the Power supply. If you are a technician then the cables are normally the green cable and any black cable. Solder these two wires to a switch. So when you flick the switch, the PSU will turn ON.
Use some fork connectors to fix these two thick cables to the Amplifier and also make a loop from the positive terminal to the REM port on the Amplifier. This is what turns ON the amplifier and without this loop the amplifier will simply not work.
Do not place the power supply unit on the floor where there is a possibility of spilled liquids getting to it.
Also make a habit of never placing anything on the PSU. And this may include bottles, clothing, plastic bags, magazines, newspapers etc. These will prevent proper circulation of air which is necessary for cooling the unit. And if anything spills inside then all hell will break loose.
Don’t place the unit on its vents. These vents help forced airflow by the fan to cool the unit.
Watch this youtube video and you will understand what I am saying much better.
The best place to mount a Computer Power supply unit is under a table or a desk where there is no possibility of it getting any spills or accidentally placing things on it.