Introduction

When it comes to power supplies for silent computing, there's one name that always comes up: Seasonic. Seasonic was originally an OEM PSU manufacturer, and they had a reputation for producing good quality, high efficiency products. It is unusual for an OEM manufacturer to bring their own products to the market since there are usually several competitors already using the same power supply. That's why it wasn't until 2002 that Seasonic decided to enter the retail market. The first power supplies had some difficulties: they came in a grey housing, there were no cable sleeves, and in contrast to many other high-end power supplies at the time there were no LEDs (Gasp!). All that customers got was a very simple looking power supply with limited to no features. The fact that Seasonic was ahead of the rest of the market in producing high quality, good efficiency PSUs with stable DC outputs wasn't clearly visible in the beginning, and few people actually knew enough about power supplies to look for those attributes.



Seasonic has traveled a long and winding road since then, and their marketing department wasn't much help. Today, Seasonic remains a very odd company in many respects, and it is difficult to compare them with many of their competitors. The size of the market for Seasonic products doesn't seem to matter; the company seems unconcerned with expanding their production facilities to meet market demands. Instead, management focuses on things like the development of newer and better products, preferring quality to quantity. That doesn't mean Seasonic is small, however; they manufacture many high-end, well known brands like Antec, Corsair, and PC Power & Cooling to drop a few names.

Of course, being manufactured by Seasonic doesn't necessarily mean that all of the brands are equally good. The consumer needs to understand that the Seasonic customer will only get the quality they can afford -- or the quality they ask for as the case may be. For example, a certain company delivered cases with pre-installed Seasonic power supplies (branded with their own name), and many of these power supplies went up in flames after a short period of time. Huge RMAs resulted from this, naturally, proving that there's a distinct difference between a Lexus and a $5,000 "luxury car" manufactured at a Lexus plant. As usual, you get what you pay for, and by refusing to pay for Seasonic quality the client received an inferior PSU. We're not here to talk about Seasonic's strategies and past business behavior, however, but rather we are here today to take a look at the new Seasonic S12II series, their latest product for the retail market.



The S12II series comes in four different wattages: 330, 380, 430 and 500. With these lower wattage power supplies, Seasonic is catering to the market where they built their reputation: silent computing. Expectations for their latest design will be high, given how popular the previous S12 and M12 series have been, both of which were huge successes for the company. The S12II features and new PCB design, though of course Seasonic seldom develops a completely new PCB layout. In most cases companies will take an older design and enhance it. (Seasonic's new X900 for example is based on a 2-year old PCB design.) This isn't necessarily a bad thing, especially if the original design is good, and Seasonic has a reputation for delivering some of the best quality power supplies on the market. That's a big compliment for any company, so let's see if Seasonic is worthy of such praise.

Package and Appearance
 

Either Seasonic had some help for their packaging this time, or else they hired a new designer. The packaging for this PSU is definitely more eye-catching than previous offerings, hopefully hoping to attract the attention of some new customers. The power supplies are well packed and include several accessories. Seasonic started the latest trend of not attaching any Molex floppy connectors directly to the PSU. Instead, an additional Molex adapter is included that provides two floppy connectors for users that continue to utilize our favorite slow storage medium. Those who have joined the rest of us in the 21st century are able to avoid a bit of extra cable clutter.
 

Like all other power supplies from Seasonic the S12II comes in a black matte coating. The fan and the fan grille are black as well, although there's a small change this time: the grille has a small blue Seasonic logo in the middle. The rear of the power supply is devoted to ventilation, other than the small area for the power cord and switch. Like many others, Seasonic uses hexagonal shaped holes for ventilation, which are supposed to create the least are resistance and produce less noise. Other than the fan intake, there are no other openings on the power supply, so the airflow only has one path to travel.

 

Cables and Connectors
 

It shouldn't come as much of a surprise that the 330W version doesn't have nearly as many cables as some other power supplies that we've reviewed. With only 330W available, users definitely shouldn't be thinking about powering multiple graphics cards or a dozen hard drives, and there are enough cables for your typical lower midrange PCs. The S12II 330W has six Molex and four SATA connectors for peripherals along with a single 6-pin PEG connector for PCI Express graphics cards. The 4-pin and 24-pin ATX connectors are standard and have a length of 50 and 55cm which is sufficient even for many larger cases. When the other hand, the peripheral connectors are all shorter and the first connectors are only 30cm from the PSU case. We had to rescale our cables graphic, but this isn't necessarily a bad design decision on Seasonic's part. They provide connectors at several different cable lengths, allowing the user to choose the appropriate connector for their specific setup. Moreover, a 330W power supply with shorter cables could be an excellent solution for many of the micro ATX cases on the market; after all, just because you want a smaller computer case doesn't mean you necessarily want a lower quality power supply.
 

The largest S12II is rated at 500W and comes with a few more connectors. There are three cables each with three Molex connectors at different lengths. The shortest distance to the PSU is again just 30cm and the largest distance is 80cm. There are two additional cables that provide three SATA connectors each. For graphics cards, Seasonic includes two 6-pin PEG connectors, one of which can be transformed into an 8-pin PEG connector by using the two additional pins that are next to it. The main 4/8 and 24-pin ATX connectors have a length of 50cm which is about average. All cables are sleeved until the first connector.

The Fans
 

The fans in the S12II series are the same for all four power supplies. Seasonic uses an ADDA AD1212MB-A7GL brushless fan with 0.33A. The 500W model has a small piece of plastic attached to the fan that is used to channel the air deeper into the case in order to improve the internal cooling.

 

The Inside



Once the power supplies are open we are greeted by this very simple looking PCB. The first impression isn't all that great as the heatsinks look small, the component arrangement seems a bit haphazard, and the coloring almost makes things look dirty. However, looks can be deceiving. The first visible difference between the two power supply models can be seen in the different coils, main capacitors, and transformer. Since the design is the same and the components are from the same manufacturer, we will continue our discussion focusing on just one of these power supplies.



The filtering stage seems to be well arranged by Seasonic; it's starts on the small PCB at the AC inlet and extends to the upper side of the main PCB directly in front of the exhaust area. Seasonic has always taken a different approach with their heatsinks, which is very simple and almost seems cheap. Instead of using more expensive extruded aluminum, they just use metal plates where the fins are punched out and bent to the side. This way is by far the cheapest way to make a heatsink, and while it might not be as efficient as an aluminum design, with the high efficiency components Seasonic uses they should not have any problems with overheating.


There's also something to be said for their smaller heatsinks: large heatsinks tend to block airflow, and while the heatsinks might stay cooler surrounding components could actually end up being hotter. With plenty of open space, Seasonic's somewhat unique approach to power supply internals may be part of their reason for their excellent reputation of silence. Of course, having the power supply that isn't rated to provide 750W or more also helps with managing heat.



The Inside, Cont'd



The secondary side looks a little disarrayed since the cables are all just hanging around. In the 330W version pictured here, there simply aren't enough cables to cover the components below; airflow should not be an issue and all of the components should remain quite cool. The cable sleeves start inside of the power supply, with no special care taken to cinch down the ends of the sleeves. The small attached PCB on the left contains safety features like OCP.

What we don't really like to see is how the cables are attached to the main PCB. Normally it should be done with clean soldering and an additional shrinking hose in case the cables get loose. The S12II uses drops of glue to cover the soldering points, and we have definitely seen better in previous models of Seasonic.



The S12II is one of the first series of power supplies to contain small "solid" (Conductive Polymer Aluminum Solid) capacitors like what is now being used on graphics cards and some motherboards. We saw some of these in the Zippy Serene as well. The solid capacitor in the S12II is connected to the 12V rails, which Seasonic mentions on their packaging. Solid capacitors typically have better longevity and heat tolerance.



Test Setup DC Outputs

As usual we are testing with our Chroma programmable loads to fully load each rail to a specific amount. This is important to get truly accurate results and not merely approximate values. The tests are conducted in two different temperature environments. One is normal room temperature of 25-26°C, while the second environment goes from room temperature and increases steadily up to 50°C. Especially during the higher temperatures we will see how good the power supplies are and what they're really made of. Components inside will perform much worse at higher temperatures, but we expect any good quality PSU to deal with such test conditions without failing.

Note: If you would like to know more about our testing methodology, equipment, and environment, please read our PSU Testing Overview.

330W Rail Loading
PSU Load	3.3V	5V	12V1	12V2	Wattage All Rails
10%	1.06	1.18	0.94	0.94	33
30%	3.19	3.54	2.83	2.83	99
50%	5.32	5.91	4.71	4.71	164
80%	8.51	9.45	7.53	7.53	260
100%	10.63	11.82	9.42	9.42	324

500W Rail Loading
PSU Load	3.3V	5V	12V1	12V2	Wattage All Rails
10%	1.42	1.42	1.54	1.54	50
30%	4.27	4.27	4.63	4.63	150
50%	7.11	7.11	7.72	7.72	249
80%	11.38	11.38	12.35	12.35	392
100%	14.23	14.23	15.44	15.44	487

To provide a better overview about the different temperatures and input voltages we test, we have decided to combine the input voltages into one graph and not four separate charts. We show an area in which the voltages have been measured. In past reviews we have seen steady voltage drops with increasing loads, and this new style of graph should make the results clearer. Each graph will show a single line and the distributed measured voltage fell inside of the specified area during testing.





Seasonic lives up to their promise of very tight voltage regulation. The voltages don't drop much from the optimal amount and hold pretty much stable under any condition we could have come up with. The 500W version doesn't seem to perform quite as well, however.



DC Outputs, Cont'd



We see minor flaws in the 5V standby rail, with the 500W version and even going out of spec at maximum load. However, this is not a major problem considering the remaining rails perform very well.





The 12V rails show a very nice regulation as well and only the 500W version shows any sort of flaw; at higher loads with high temperatures the second 12V rail drops a bit further. In all of the remaining 12V testing, we didn't see the voltage of either power supply dropped below 11.90V at lowest. Seasonic has especially worked hard on voltage regulation and did a great job in stabilizing the rails.



Standby Efficiency

330W Results:



500W Results:


With just 1W to 1.6W the S12II are consuming very little power during shut down mode. Of course it would be better if a power supply could consume nothing while doing nothing, but that's unfortunately too much to ask. A small amount of power is required for features such as Wake On LAN to function, among other things. The standby efficiency is average from both PSUs.

Efficiency



With both power supplies having up to 85% efficiency, the 330W version might be the most efficient small performing power supply in the market. Even with a low 100VAC input voltage, both power supplies still manage to reach 83% efficiency -- this comes at a 100W load on the 330W and a 150W load on the 500W model. High efficiency is achieved a loads ranging from around 20% up until 90% -- and even higher if you have a 230VAC input voltage. Both power supplies manage more than 80% efficiency at almost all loads.

Power Factor Correction



Power factor correction has been good for most of the Seasonic power supplies and with the S12II we don't see any difference. With a higher input voltage PFC is always worse, and especially with the 330W version it doesn't appear to be all that great. However, keep in mind that a 30% load on the 330W power supply equates to a power draw of 100W, which is the same as a 20% load on the 500W model.



Temperatures, Fan Speed and Acoustics




Both temperature curves appear similar, and naturally the 500W version gets hotter. If you compare the two power supplies at similar loads in terms of Watts, the internal temperatures are almost the exact same in most cases. It's only once the 500W model exceeds 330W (66% load) that it clearly gets warmer. The third heatsink gets quite hot on the 500W unit, reaching 80°C at maximum load. This heatsink is located in the middle, which is something of a dead spot in terms of airflow and that probably accounts for the higher temperature. We have seen worse, but the still rising temperature suggests that the 500W power supply may not survive long in higher temperatures running at full load.



In contrast, when testing at normal room temperatures the middle heatsink on the 500W version only reaches 72°C. The small 330W stays under 60°C and should not have any difficulties regardless of operating environment (within reason).



If you're wondering what happened to the results, please direct your eyes towards the lower reaches of the charts. The 330W Seasonic reaches a maximum noise level of 25dB(A), while the 500W achieves an earsplitting 28dB(A). It's not easy to describe the noise of the fans since there simply isn't much to hear. The fans are whisper quiet and about the only thing you can hear is the sound of moving air if you hold your ear right next to the power supply. Quiet fans usually mean very little airflow, and without a proper design this could be problematic. However, as we have already seen in the temperature graphs there weren't any serious problems during stress tests lasting over six hours.



The 330W S12II shows a very slow rotating fan that only reaches 1350 RPM, which helps to explain the low noise levels. The 500W model starts at around 850 RPM as well, but fan speed begins to increase passed the 50% load mark and reaches its maximum speed in stress testing at the 70% load mark. At normal room temperatures, the full speed is only reached at 100% load, so for the vast majority of users the fan will remain extremely quiet during use.



Conclusion

Anyone who has read about Seasonic on the Internet has almost certainly seen comments about their good quality, high efficiency, and extremely quiet designs. After testing two of the latest models we can definitely validate these comments. The S12II is one of the best power supply series on the market, sufficient for all but the most demanding systems. By looking at the lowest and highest rated models, we wanted to show the full range of what Seasonic offers with their new S12II series.

While there are many similarities between the two units, however, they still cater to different market needs. The small version is very attractive for users looking at mATX or HTPC computers for the living room where silence is the primary concern and a large power draw often isn't necessary. The 500W model can serve that market as well, but it can also support a decent high-end system and is only limited by the two PEG connectors it offers. As long as you don't need to run HD 2900 XT CrossFire or 8800 GTX SLI, there is very likely a Seasonic S12II that can fit your needs.

Efficiency Comparison


In the efficiency comparison we show the highest measured result of each tested unit. Both the largest and smallest Seasonic S12II power supplies score an 85% efficiency rating using a 230VAC input. For the most common loads, regardless of input voltage efficiency should still stay above 80%.

The DC outputs were good and stable, and we found very little to complain about with either unit. The cables of both units are of reasonable length with up to 80cm of the 500W version. The 330W version has slightly shorter cables and offers a wide range of connectors with a maximum length of 65cm. given that it's highly doubtful anyone would be looking to place the 330W version into a big tower, the length of the cables is not a problem; in fact, for use in small boxes and HTPC systems the shorter cable lengths are even preferred. The 330W version offers a single 6-pin PEG connector capable of handling anything up to a moderate high-end GPU. The bigger version has two 6-pin PEG connectors, one of which can also function as an 8-pin PEG connector. This is sufficient for powering more moderate SLI/CrossFire configurations, or for running a single top-end graphics card.

Anyone searching for a very silent power supply with good quality and performance will find the S12II series very attractive. They have delivered the lowest noise levels out of any power supplies we've tested so far, with the 500 model reaching a maximum noise level of only 28dB(A) -- practically silent, even in a worst-case scenario. Keep in mind that this kind of low noise is only possible through the use of a very slow turning fan. In the test we measured up to 1350 RPM with the 330W version and up to 1850 RPM on the 500W model. Slow turning fans do not move much air through the power supply, and that means in a poorly designed power supply you would get incredibly high temperatures and likely high failure rates. However, this doesn't apply with the S12II since the heatsinks stay relatively cool and Seasonic uses high-end components rated for up to 105°C. Having high-efficiency certainly helps.

Finally, let's take a look at the prices, and unfortunately this is the one area that will cause many users to think twice. Seasonic power supplies are definitely not cheap, especially considering the power ratings. The S12II 500W sells for around $110, and while we couldn't find the S12II 330W (we could only locate the older S12 330W), the S12II 380W starts at around $63 -- plus shipping, of course. Prices are similar in Europe, and in Germany we found prices of €82 ($114) and €46 ($64), excluding the shipping. Users will need to give careful thought to whether or not the features and performance offered can justify the price. For users looking to build a really silent system, the answer is a resounding yes. Even if silence isn't your primary concern, however, Seasonic's power supplies are definitely worth your money.