Seasonic S12-500 & S12-600 Power Supplies

TEST RESULTS

For a fuller understanding of ATX power supplies, please read our article Power Supply Fundamentals & Recommended Units. Those who seek source materials can find Intel's various PSU design guides, closely followed by PSU manufacturers, at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to the article SPCR's Revised PSU Testing System. It is a close simulation of a moderate airflow mid-tower PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately with its output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a precise high power load tester which allows incremental load testing all the way to full power for any non-industrial PC power supply. Both fan noise and voltage are measured at various standard loads. It is, in general, a very demanding test, as the operating ambient temperature of the PSU often reaches >40°C at full power. This is impossible to achieve with an open test bench setup.

Great effort has been made to devise as realistic an operating environment for the PSU as possible, but the thermal and noise results obtained here still cannot be considered absolute. There are far too many variables in PCs and far too many possible combinations of components for any single test environment to provide infallible results. And there is always the bugaboo of sample variance. These results are akin to a resume, a few detailed photographs, and some short sound bites of someone you've never met. You'll probably get a reasonable overall representation of that person, but it is not quite the same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: One very important point is that the while our testing loads the PSU to full output (even >600W!) in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 65W and 250W, because it is the power range where most systems will be working most of the time. To illustrate this point, we recently conducted system tests to measure the maximum power draw that an actual system can draw under worst-case conditions. Our most powerful P4-3.2 Gaming rig drew ~180W DC from the power supply under full load ? well within the capabilities of any modern power supply. Please follow the link provided above to see the details. It is true that very elaborate systems with SLI could draw as much as another 150W, but the total still remains well under 400W in extrapolations of our real world measurements.

SPCR's high fidelity sound recording system was used to create MP3 sound files of this PSU. As with the setup for recording fans, the position of the mic was 3" from the exhaust vent at a 45° angle, outside the airflow turbulence area. The photo below shows the setup. All other noise sources in the room were turned off while making the sound recordings.

Ambient conditions during testing were 21°C and 18 dBA, with input of 120 VAC / 60 Hz measured at the AC outlet.

The results of the testing were so close between the two samples that they might as well have been identical. The differences were typically within 1%. Rather than clutter up the article with two complex charts that have the same data, the two sets were combined. The worse of the results obtained for the two samples are presented here. Naturally, only the S12-600 was tested at 600W.

ANALYSIS

1. VOLTAGE REGULATION was excellent, within -/+2% on all lines at all test loads, except for the 3.17V reading at full powerful, which was -4% off. The low and high voltage seen on each of the main lines is shown below. Unless otherwise noted, the lowest voltage recorded were at the highest loads.

• +12V: 11.91 to 12.12
• +5V: 4.90 to 5.02
• +3.3V: 3.17 to 3.32

2. EFFICIENCY was excellent, as expected of these 80 PLUS certified power supplies. The efficiency / power output ratio curve was quite flat from below 20% of rated load all the up close to maximum power. The flat 87% efficiency obtained from 200W to 400W is most impressive. In practical applications, these PSUs will be very tough to beat for energy efficiency, with their combination of high AC/DC conversion efficiency and active PFC.

3. POWER FACTOR was just about perfect across the power range.

4. TEMPERATURE: The high efficiency combined with the large heatsinks and effective airflow in these PSUs to provide the best in / out air temperature rise recorded in our PSU tests. At all power loads of 250W or lower, the temperature rise was only +3°C. It gradually rose to +7°C at full power load. This compares very favorably with many PSUs that hit +7~10°C in / out temperature rise by 50% load. It is not unusual for 15°C to be exceeded at full power loads. This means that the S12-500 and S12-600 are very effectively cooled and overheating should rarely be a cause for concern.

5. FAN, FAN CONTROLLER and NOISE: The test environment is live, so readings are higher than would be obtained in an anechoic chamber readings, due to reflections and reinforcement of sound waves off the walls, ceiling and floor.

The start SPL of 21 dBA/1m was 3 dBA higher than that measured on the original version of the fan-cooled PSU champion (for noise), the S12-430. But it was still extremely quiet. The new Adda-fan equipped 430 is only one decibel quieter. (See postcript to S12-430 eview.) The first hint of fan noise increase was heard (and measured) at 150W output or ~31°C intake temperature. The overall noise stayed quite modest until past the 250W load. When listened up close. the dual ball bearing fan has a bit of the typical ball-bearing chatter, but it is very subdued, and based on our recollection, much quieter than the earlier 5-blade Yate Loon fans first used in these models.

Like the S12-430, the fan controller in these high power PSUs showed exemplary behavior. The ramp up of the fan as load increased was gradual. Compared to the S12-430, the overall noise level was typically 2-3 dBA louder through much of the power range. As the power load went past 300W and the fan voltage climbed beyond ~8V, the higher capacity of the medium speed in the 500 / 600 began to make a bigger difference ? in airflow and the resulting turbulence noise. For those who have a need for such high power capability as offered by the S12-500 and 600, the increased noise at high power is a modest price to pay, especially when acoustics at typical power loads (<300W, even for high power gaming rigs) is so well behaved.

In actual use inside a typical modern PC, we expect these PSUs to rarely ramp up beyond ~30 dBA/1m. Extended high loads are required for the temps to rise high enough to cause further ramping up of the fan.

CONCLUSIONS

The new and improved S12-500 / 600 power supplies find Seasonic at the top of their game. These high power models pick up where the S12-430 leaves off and continue on quietly, steadily delivering power on demand. Tops for efficiency, for low noise, for stable high power delivery, and for the minimalist approach that strikes a chord of quality for many users.

Our own testing confirmed that the 500 and 600 do indeed reach 80% and better efficiency at 20%, 50% and 100% loads demanded for the 80 Plus program, which has certified both models. The 80 PLUS test results are available as downloadable PDF files and worth a careful examination. So far, Seasonic appears to be the only PSU brand with a retail presence to have achieved 80 PLUS approval.

While they do not plumb the quiet depths the way the original S12-430 did, the 500 and 600 are nearly as quiet at low to medium load and can take on any PSU of similar power capacity without any acoustic handicap. In fact, the reverse is true: There is not a single PSU we know of that can produce so much stable power as the S12-600 and stay as quiet. At the more likely loads of <250W, the noise level stays well in the mid-20s (in dBA@1m), which is competitive with the majority of quiet PSUs.

We wrote at the end of the original S12-430 review that about the only thing more a gamer might ask for is support for the 6-pin power connector used by power-hungry PCIe VGA cards. Two such connectors are now available in the S12-500 and the S12-600. If you seek quiet, stable, high power without flash, look no further than the S12-500 and the S12-600.

Our thanks to Seasonic USA for the S12 samples.

NOTE: A postscript has been added to the Seasonic S12-430 review to investigate the effects of the change to the Adda fan.

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