So, you’ve got a car audio amplifier but need a power source outside of your vehicle? A PC ATX or server power supply can be a surprisingly effective and budget-friendly solution. While they typically output 12V rather than the 14.4V car electrical systems often provide, they still offer ample power for many car audio setups, especially for testing or bench setups. You might experience a slight dip in maximum rated amplifier power, but for many applications, this is negligible. Another option is using dedicated 12V LED power supplies, some of which allow for minor voltage adjustments, often in the 11-14V range.
To get a standard PC ATX power supply to power on, you’ll typically need to locate the green wire in the main connector and connect it to any black (ground) wire. A simple switch can be used to easily toggle the power supply on and off by shorting these wires together. For connecting your amplifier, you’ll need to carefully cut off the standard PC connectors and group all the yellow 12V wires together, and likewise bundle all the black ground wires. These will become your positive and negative terminals for connecting to your car amplifier.
A word of caution: modifying an ATX power supply to increase the voltage output to around 14V is possible, but it’s only recommended if you have a solid understanding of electronics. These power supplies contain capacitors that can hold dangerous levels of voltage even after being unplugged, posing a significant electrical shock hazard. If you’re not comfortable working with electronics, it’s best to stick to the stock 12V output for safety.
Now, let’s talk about power requirements. This is where understanding your amplifier’s class – either AB or D – becomes important. To calculate your power needs, sum up the RMS power ratings of all your amplifier channels. For instance, a 2-channel amplifier rated at 250W per channel totals 500W. For class AB amplifiers, a good rule of thumb is to multiply this total power by 1.5. For more efficient class D amplifiers, multiply by 1.2. So, our 500W example would draw approximately 750W for class AB or 600W for class D. It’s wise to add an additional 50W as headroom.
Dividing this final wattage by 12V gives you the approximate current draw in Amps. For our class AB example: (750W + 50W) / 12V ≈ 67A. For class D: (600W + 50W) / 12V ≈ 55A. Compare this calculated current with the fuse ratings on your car amplifier. Ideally, your power supply should be capable of providing slightly more current than your amplifier’s total fuse rating. Undersized power supplies can prevent fuses from blowing in overload situations, potentially damaging wiring or even causing a fire. This is also why class D amplifiers are often favored in high-power applications due to their lower current draw compared to class AB for the same output power – in our 500W example, that’s a significant 200W difference in power supply demand.
