Antec Phantom 500

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An informal test was run on a Phantom 500 in a system that was built by Mike at the time of testing. The following components were used:

Altogether, this setup drew ~160W AC when running CPUBurn. This equates to about 135W DC output. The system was burned in for a day running Prime95 continuously. CPUBurn was also run on the machine for about two hours. The room ambient varied from 22°C to 25°C. During this time, the PSU fan never turned on, meaning that the Phantom 500 was effectively fanless. At no time during this load testing did the system exhibit any instability. The measured SPL during CPUBurn was measured at ~27 dBA at 1m from the front, top or sides. The acoustic character was predominantly the benign broadband wind noise of the smooth, slowly spinning fans. When the hard drives moved into seek, the SPL jumped 2~3 dBA, but in idle, the Raptor HDDs were amazingly quiet. The buzzing reported during the testing was occasionally present, but it could only be heard when directly behind the PSU and a foot way; practically speaking, it was a non-issue.

The system was not built with ultimate quiet as a target, but rather, high performance, stability and reliability at up to 30°C ambient room temperature — and very low noise. The original PSU choice was a Seasonic S12-430, but its main ATX cable was stretched a little too tight for comfort due to the positioning of the PSU so far from the motherboard. The Phantom 350 was a possible choice, but for higher reliability, the fan and the higher power capacity of the Phantom 500 seemed a better match for this system. After a couple hours of being turned on, especially when running CPUBurn, the top and back case panels near the PSU became somewhat warm to touch. The PSU back panel was a bit warmer, of course, but not at all uncomfortable to touch. Unfortunately, temperatures were not taken, but if I had to guess, I'd say the back of the PSU was not much higher than 40°C.

The configuration and mods for this case would have been the same with the S12. The additional 80mm fan under the PSU just seemed wise, given the hot running tendency of the 10K Raptor HDD positioned below it. (Even with the S12-430, airflow for the HDD was pretty modest because the 120mm fan in the S12 runs at such low speed.) Subjectively, from the user's point of hearing with the PC on the floor by or under a desk, the extra 80mm fan does not add to the overall noise. The two biggest noise challenges of this system were two small fans: One on the video card, and especially the one on the motherboard northbridge chip. Allowing the latter to ramp up easily destroyed the silencing work on all the other components; its high pitched, loud whiny whooshing at full speed was difficult to tolerate for more than a minute or two. It's only the fan controller in the BIOS that saved this DFI NF4 board from being summarily rejected.


The Phantom 500's extremely high efficiency is noteworthy. We find ourselves crowning a Phantom as efficiency champion once again. There must have been tweaks and production improvements to the circuit design of the original Phantom 350 to improve the efficiency at lower output levels, and to maintain efficiency above 80% throughout most of the output range. It may be possible that current production Phantom 350 samples also exhibit improved efficiency.

Its $200 recommended retail price is the same as the Phantom 350. At time of writing, the Phantom 350 can be found for as low as $130 from discount online stores, so the 500 can probably be expected to be available for a similar price as availability expands. The pricing suggests that the 500 is positioned alongside the 350 as an alternative, not as a higher rank model.

If the Phantom 500 had been equipped with a smoother fan and its controller configured so that the fan would start at say ~300W and ramp up without the quick variations in speed that causes annoyance, then there would be no need for the Phantom 350 at all. As it is, the two represent a somewhat complex choice with overlaps in suitability; neither quite replaces the other.

It is important to remember that neither the 350 nor the 500 are intended to be used in a fanless system. The Phantom 500 manual notes, "your chassis must be well-ventilated... make sure the exhaust fans installed in your PC chassis can cool the whole system without the help of a power supply fan." This advice is pertinent to every fanless ATX PSU on the market.

For the silent PC seeker, our general recommendation is to keep the overall system power as low as possible so that there is a minimal amouint of heat to content with. Our test system above is a good example of a powerful system that still does not even reach 150W DC maximum output. In this system, it would make no difference which of the two Phantoms was used, because the the 500's fan would probably not turn on unless ambient temperature soared, perhaps to >30°C. Some would say the 500 is a better choice for this system because it will be just as quiet as the 350, yet protect itself in a thermal emergency. Others would say they'd prefer to know that there is no fan to ever turn on and keep the thermal management in their own hands. The bottom line is that if the temperature at the PSU "intake" can be kept below ~33°C all the time, the 500 will be just as silent as the fanless 350. The fan trigger point is affected by ambient temperature, and it can also be controlled by adjusting the case airflow, especially in the vicinity of the PSU.

There is a stronger case for the Phantom 500 for the inveterate, power-hungry gamer who seeks a quiet PC. There are lots of such folks floating at SPCR these days; yes, even gamers are starting to hear the call of the silence siren. These PC users still want to run a thermally extreme system -- something like dual >75W VGA cards in a loaded high power system with a CPU that draws >100W. Or perhaps a dual-CPU system (since the Phantom 500 has an 8-pin EPS12V connector). Such a system could push the fanless 350 to its output limits and challenge its ability to keep itself cool. The Phantom 500's built in fan would certainly keep it cooler, and it would provide the necessary power. At the same time, when the system is in idle, reduced power consumption would likely bring the temperatures in a well-designed system down to the point where the Phantom 500 fan would turn off.

In this kind of application, the Phantom 500 has to compete with more conventional but still very quiet fan-cooled PSUs, such as the Seasonic S12-430 (or the slightly less quiet S12-500). Even though its maximum power is lower than the Phantom 500, 430W is probably still enough power for all but the most extreme gaming PCs. The main advantage of the Phantom 500 is that at lower power levels, it is silent, while the more conventional quiet PSU runs very quietly. But then there is price to consider, and whether or not the rest of the system components are quiet enough to make that PSU noise difference audible.

The Phantom 500 is also a good choice for silencing newbies with deep pockets. The cooling fan is good insurance against burning the power supply in a system with inadequate airflow. The user-selectible options on the fan controller let the end-user determine their own level of thermal tolerance, although most newbies will probably just set it to "3" and forget about it.

Adding a fan to a "fanless" power supply seems counterintuitive, but it does provide a fail-safe option that is not present in the Phantom 350. In most circumstances, the Phantom 500 will function well as a fanless power supply so long as airflow through the case is well managed.

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Much thanks to Antec Inc. for this Phantom 500 sample.

POSTCRIPT: Efficiency Correction
October 22, 2005

Recently, we discovered that our power supply testing equipment and methodology were providing erroneously high efficiency results. In general, the biggest errors occurred at higher output load points above 300W. At lower output levels, the efficiency error was often no more than one or two percentage points. No other tested parameters were significantly affected.

Through a fairly arduous process of discovery, analysis and old fashioned problem solving, we modified our testing equipment and methodology to improve the accuracy of the efficiency results and described it all in the article SPCR's PSU Test Platform V.3. As part of this revision, we re-tested most of the power supplies on our Recommended PSU List. In most cases, the same sample was used in the second test.

The corrected and original efficiency results for all the re-tested PSUs are shown in in the article, Corrected Efficiency Results for Recommended Power Supplies. The relative efficiency of the tested power supplies has not changed. If the tested PSUs are ranked by efficiency, the rankings remain the same whether we use the original results or the new results.

This data is also being added to relevant reviews as postscripts like this one.

Target Output
Actual Output

In this case, our original efficiency calculations were way off across the board. It's not clear why they were so far off, as most other test results were reasonably close at lower power output points. The extreme high efficiency results we obtained originally have dropped mostly into the low 80s and high 70s — still very good results, and bettered only by the Fortron Zen among fanless PSUs.

Discuss this article in the SPCR Forums.

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