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Five power supplies compared

Because your PC deserves better power
— 12:00 AM on August 5, 2003

I'VE SAID IT before and I'll say it again: power supplies are continually the most neglected PC component. It boggles my mind how many systems I see with swanky LCD monitors, high-end graphics cards, screaming-fast processors, and flashy artistic modifications all powered by no-name power supplies that are often the root of stability problems. Would you dare put cheap gas in a Porsche? Of course not, yet I continue to see enthusiasts putting cheap power into their high-end PCs.

I suppose the assumption is that all power supplies of similar wattage are created equal, but that couldn't be farther from the truth. PC power supplies can differ in not only more obvious environmental attributes like noise and heat levels, but also in the quality of power they deliver.

Last year, I compared four different power supplies from Antec, Thermaltake, and Vantec. Antec's TruePower line came out as our Editor's Choice in that comparison by delivering tight DC voltage tolerances with low noise levels. Today, I've rounded up five brand-new power supplies from Ahanix, Antec, Enermax, Vantec, and Zalman to compare with each other and our previous favorite. I've updated our power supply testing gauntlet, too. Not only will we be looking at DC voltage tolerances and noise levels, we'll also take a peek at each power supply's impact on system temperatures and measure its AC ripple voltage.

Which power supply stands out from the competition as being the quietest, coolest, and cleanest source of PC power? Read on to find out.

The specs
Power supplies are usually bunched together based on their total output wattage, but there's more to wattage than total output. Today we're dealing with 400 and 550W power supplies, and there's quite a bit of variety when it comes to distributing that total wattage over available voltage lines.

Maximum output (W)

DC Output +3.3V +5V +12V -5V -12V +5Vsb
Ahanix SilenX 400W 52.8 200 336 1.5 9.6 10
200 336
Antec TrueControl 550W 105.6 200 288 2.5 12 10
Antec TruePower 550W 105.6 200 288 2.5 12 10
Enermax EG651P-VE(FMA) 550W 118.8 180 432 5.0 12 11
200 432
Vantec Ion 400W 85.8 200 192 12 4 12.5
380 28
Zalman ZM400A-APF 400W 92.4 200 180 1.5 9.6 10
380 20

While Enermax, Vantec, and Zalman's power supplies all share voltage between the 3.3 and 5V rails, Antec's TruePower and TrueControl models have dedicated output circuitry for each rail. This dedicated output circuitry comes in handy when a system has an unbalanced overall load that's biased towards the 3.3 or 5V line. If the 3.3 and 5V lines don't have to share wattage between them, each line can be loaded to its theoretical limit.

Overall, Enermax's EG651P-VE(FMA) offers more wattage on the 3.3 and 12V rails than any other power supply we're looking at today, but only 180W on the 5V rail. Ahanix's SilenX is a little weak on the 3.3V line, but its maximum 12V wattage is quite strong. Vantec and Zalman's offerings, on the other hand, offer relatively low 12V wattages but plenty of power on the 5V line.

For reference, here are the maximum output currents for each power supply's output lines:

Maximum output current (A)

DC Output +3.3V +5V +12V -5V -12V +5Vsb
Ahanix SilenX 400W 16 40 28 0.3 0.8 2.0
Antec TrueControl 550W 32 40 24 0.5 1.0 2.0
Antec TruePower 550W 32 40 24 0.5 1.0 2.0
Enermax EG651P-VE(FMA) 550W 36 36 36 1.0 1.0 2.2
Vantec Ion 400W 26 40 16 0.8 1.0 2.5
Zalman ZM400A-APF 400W 28 40 15 0.3 0.8 2.0

Other than Enermax, whose EG651P-VE(FMA) offers the same maximum amperage on the 3.3, 5, and 12V lines, manufacturers tend to offer higher currents on the 5V line.

Theoretical specs are only so exciting, so let's dive in and take a closer look at what each power supply has to offer.