Seasonic S12II SS-430GB 430w ATX PSU Page: 1

When it comes to silent yet powerful PSU's, Seasonic are often one of the first companies to be mentioned. In business for over 30 years, Seasonic certainly know what they are doing when it comes to manufacturing power supplies and some of their previous models have reached an almost iconic standing among the silent PC community.

Today we'll be looking at Seasonic's latest addition to their silent line-up: the S12II series. Based around the extremely popular S12 series released back in 2005, the S12II series promises quiet operation combined with performance and all the latest connectors required for the modern PC. With models ranging from 330w to 500w, the S12II range certainly isn't aimed at those demanding huge amounts of power (the X900 fills that gap nicely!), but more for those of us who want to avoid our PC's sounding like jet engines.

However, before we get down to business let's find out a little more about Seasonic with this extract taken from their website:

About Seasonic

Since the incorporation of Sea Sonic Electronics Co., Ltd. in 1975, we have maintained our focus on research and development and the production of quality power conversion products.

For the past decades, supported by cutting edge technology based upon a strong research and development team, Sea Sonic Electronics has provided timely and professional solutions to meet many of the IT industry's requirements.

For the future, we will continue our philosophy of dedication; innovation, professionalism and 4G's (Great Technology, Great Quality, Great Service & Great Price) in order to maintain our goal of continued long-term business partnerships and create "win-win" situations for our customers.


The following information has been taken directly from Seasonic's recent press release and Nanopoint's (Seasonic's UK Distributor) website:

The S12II series is made up of 330, 380, 430 & 500 watts units. Each of the Windows Vista™ ready power supply not only meets but also surpasses the stringent 80 PLUS® requirements. This feature combined with a power factor correction factor of 0.99, total computer system energy usage can be reduced by up to 20%, surpassing even the original S12’s performance levels.

Technically, the S12II is a dual 12V rails Double Forward Converter circuit design. High grade Conductive Solid Polymer Aluminum Capacitors are used to further enhance performance and reliability. These capacitors offer improved heat resistance and conductivity over the market standard electrolytic capacitors

• 430W ATX power supply
• Multiple +12-V Outputs: Enhanced +12V current capability broadens utilization possibilities
• Super high efficiency (up to 85%): Optimal solution for lower energy consumption, noise & heat
• Active power factor correction (99% PFC): Reduces line loss & power distortion
• Double forward converter circuit design: Advanced topology for highest efficiency
• Conductive polymer aluminium solid capacitors: Advanced ultra-low resistance, high temperature capacitors on the critical 12V rail
• 12cm ball bearing cooling fan: Increases airflow & lifetime and reduces rotation speed and noise
• Smart & silent fan control (S2FC): Smart thermal control to balance noise & cooling
• Soft-mounting rubber cushions: Reduces fan rotation & vibration noise
• Ultra ventilation (honeycomb structure) Minimized airflow resistance for maximum cooling
• All in one DC cabling design: Supports PC, IPC, workstation, server & dual CPU systems
• Universal video card support: Supports new PCI-E video card technologies
• Universal AC input (full range): Plug & run safely anywhere in the world
• 3 year warranty: Our commitments to superior quality

Seasonic have clearly made some improvements to the S12II series over its S12 predecessor, with the unit boasting up to 85% efficiency over the original S12's 80%. In addition to this, the S12-II has also been fitted with polymer aluminium solid-state capacitors which offer longer life and more stable voltage at higher temperatures than their electrolytic counterparts.

Seasonic S12-II 430w Specs Label

The SS-430GB also features dual +12v rails each rated at 17 amps, with a total output of 360w (30 amps) across both rails simultaneously. Although this may not meet the extreme power requirements of the modern SLI/Crossfire setup, it will certainly be more than enough for any single VGA card PC system.

Now that we've gotten acquainted with Seasonic and the basic specs of the S12II, let's take a look at the unit itself over the next page...

Seasonic S12II SS-430GB 430w ATX PSU Page: 2

I think it's fair to say that Seasonic have always been considered a "no-nonsense" PSU manufacturer. For this reason it's no surprise that their product packaging has always followed the same professional yet simplistic themes - some examples of which can be found in our previous X900 and M12 reviews.

Seasonic S12-II Packaging Seasonic S12-II Packaging

Seasonic S12-II Packaging Seasonic S12 Packaging

This theme is certainly continued on the S12II series, with the SS-430GB being contained within a black cardboard box printed with fairly simplistic blue/white glowing effects and not a trace of any CGI graphics anywhere! In all honesty, the S12II probably won't stand out much on a retailers shelves to the average gamer or thrill seeker, but then the unit doesn't have all the flashing fans and glowing modular plugs to satisfy their needs anyway.

Putting aside the looks, Seasonic have done a very good job of fitting all of the specifications and other information about the S12II on each of the 6 corners of the box without overwhelming potential buyers with information. Most of the information we've already covered in the specifications section on page 1, but as we can see from the images above, the S12II series also comes with a 3yr warranty, 120mm ball bearing fan, rubber mounting cushions (to reduce vibrations) and support for the latest PCI-E graphics cards.

Seasonic S12-II Open Box Seasonic S12-II Contents
Open up the box and we can see that Seasonic has opted to package the SS-430GB in a bubble wrap bag. This should help to keep the unit separate from the cables and accessories that might otherwise scratch its painted surface. While we're on the subjet of accessories, lets see what's included in the box:

- Mains cable
- ATX case screws
- Seasonic case sticker
- Manual
- Molex-to-Floppy adapter cable

As we can see, Seasonic has included everything neccesary to get you up and running, without including any unnecessary extras that might bump up the cost of the unit.


To say that we were expecting anything more than a plain black unit from Seasonic would be a lie. After all, every other unit we've reviewed from Seasonic in the past has been somewhat of an inconspicuous affair. This certainly isn't a bad attribute, as after all, most flashy and colourful unit's we've tested in the past have failed to impress where it really matters.
Seasonic S12-II 430w Back Seasonic S12-II 430w Bottom
Unlike most of the standard black PSU's we've tested in the past, the coating on the S12-II has a rough feel to it and actually proved to be extremely rugged when we attempted to scratch it with a knife. This is great news for those of us who have cases with tight fitting PSU compartments that are often responsible for leaving nasty gashes in a PSU's paint job.

As you would expect from a PSU cooled by a 120mm fan, the S12II series has a honeycomb mesh at the back of the unit along with a standard sized power switch. At the bottom of the unit, Seasonic have used a painted black wire fan grill complete with a Seasonic badge. This really finishes off the look of the unit, and is a much needed aesthetic improvement over the generic silver grill found on the M12 series.

Seasonic S12-II 430w Back Seasonic S12-II 430w Side
The back and sides of the unit are fairly standard with the usual specification and warning stickers. Unfortunately, beyond this there's not really much else to talk about, so let's move on to the next page where we have a poke about inside.

Seasonic S12II SS-430GB 430w ATX PSU Page: 3
Internal Components

In the past, many people have judged the quality of a PSU on its weight and size of internal components. However, with many manufacturers moving on to newer and more efficient ways of designing their PSU's, it has become increasingly obvious that this is no longer a reliable method for gauging a power supply's quality.

Seasonic S12-II 430w Inside Seasonic S12-II 430w Inside
Bearing in mind that this is actually a 430w PSU we're looking at here, the SS-430GB actually has fairly "beefy" internals. Starting at the middle of the unit, we can see the main transformer (responsible for both of the +12v rails), with a smaller transformer sitting to the right (for the +3.3v and +5v rails). In the far right corner is the main capacitor, which is once again larger than I'd expect to see in an average ~400w unit.

As the S12II series is effectively cooled "bottom-up" by a 120mm fan, Seasonic have also taken the liberty of designing the heatsinks in a way that will create turbulence in the airflow thus providing more effective cooling. This should certainly help to keep the three rows of mosfets attached to heat sinks fairly cool.
Seasonic S12-II 430w 120mm Fan

All other Seasonic units we've tested in the past have made use of ADDA fans, and from the image above it's certainly true to say that the S12II series is no different. As i'm sure everyone already knows, 120mm fans generally offer a much better CFM / dBA ratio than their 80mm counterparts, but let's check the exact specs of this fan to see how it might fair in a silent environment:

• Model: AD1212MB-A71GL
• Size (mm): 120x120x25
• Bearing: BALL
• Speed (RPM): 2050
• Airflow (CFM): 80.5
• Noise (dBA): 38.0

With a noise rating of 38dBA, the ADDA fan certainly doesn't win any awards for being the quietest fan on the planet when running at +12v. However, Seasonic will have undoubtedly installed a fan speed controller in the S12II series to ensure that the fan runs no faster than required at any specified load/temperature level. We'll find out for sure over the next page exactly how loud things get under full load.

Cables & Connectors

It's good to see that Seasonic have decided to sleeve all cables right to the very last connector. Many manufacturers only sleeve some of the cables, or sleeve up to the first connector on every cable leaving the PSU looking a bit unfinished. The sleeving job is professional with cable ties holding the sleeving in place, and heat shrink keeping everything neat and tidy.

Seasonic S12-II 430w Cables Seasonic S12-II 430w Cables

In addition to this, all connectors on the S12II are finished in black, with the molex connectors adopting the 'easy grip' design - which should make removal of the connectors from devices easier.

Seasonic S12-II 430w ATX

Seasonic S12-II PCI-E Seasonic S12-II 430w EPS12v
The ATX connector on the S12II is native 24-pin. However, as you can see above, a small block of 4 connectors can be broken off to switch the connector to 20-pin, thus making it compatible with older motherboards. As some motherboards still make use of the P4-12v 4-Pin connector, Seasonic have chosen to include two separate cables for P4-12v (4-pin) and EPS12v (8-pin) standards.

Seasonic S12II SS-430GB 430w ATX PSU Page: 4
Load & Efficiency Tests

To provide our readers with the most accurate results, Overclock3D uses a custom built PSU load tester on all reviews. This not only gives much more reliable results than the testing methods employed by other sites, but also allows for all current and future review results to be compared side-by-side.

Efficiency tests are performed by measuring the wattage consumed by the power supply at the mains (Mains Draw) against the power consumed by the OC3D power supply stress tester (PSU Load). These results may not be 100% accurate, but have proven to be extremely close to results obtained from professional equipment.

+3.3v Rail0w33w66w
+5.0v Rail0w50w100w
+12v Rail(s)0w120w240w

Seasonic S12-II 430w Load Tests
There's no denying that the SS-430GB showed excellent voltage stability across all of it's main rails with minimal difference between idle and full load results. At no point did any of the results fall outside of  ATX specifications, showing once again that Seasonic invest their R&D where it matters - in the performance.
Seasonic S12-II 430w Efficiency Tests
The S12II series is quoted as having "up to 85% efficiency" and the results obtained from our testing equipment are certain testament to this. At 203w load we saw the efficiency of the unit comfortably hit 84%, with the full load (406w) results bordering on almost 85%.

Temperature Testing

In our continuing efforts to make power supply reviews more thorough, rather than simply checking voltage stability, Overclock3D will now be recording the temperature of each PSU as it undergoes testing. Temperature recordings will be taken from the underside of the PSU's outer casing at 0%, 50% and 100% load levels using a laser infra-red thermometer in an attempt to gauge how much heat is likely to radiate into the end-users case.
Seasonic S12-II 430w Temperature Tests
Being a fairly low wattage unit by today's standards, we certainly weren't expecting any extreme levels of heat to be output by the unit. The results obtained at 0%, 50% and 100% load levels certainly reinforced this theory, with only a 12°c rise in temperature at full load (100%) over the ambient and idle recordings of 22°c.

Noise Level Testing

Possibly the hardest part of any PSU review is summarising the level of noise given out by the unit. The threshold for what is considered 'noisy' varies from person to person and therefore what I may consider a quiet unit, another person may consider extremely loud. For this reason, all reviews from this point forward will be using a dBA meter to measure the level of noise output by the PSU.

All noise measurements are taken in a quiet room with the dB(A) meter located 30cm away from the exhaust fan on the unit at 0%, 50% and 100% load levels.
Seasonic S12-II 430w Noise Output Tests
With only a 3dB(A) increase in noise output from 0% load to 100% load, it's certainly fair to say that the SS-430GB should more than satisfy the needs of any quiet PC enthusiast or those seeking a silent PSU for their HTPC system. I literally had to put my ear up close to the fan before I could hear any kind of  'whirring' or air movement. Great work Seasonic!

Seasonic S12II SS-430GB 430w ATX PSU Page: 5
Conclusion & Awards

The Seasonic S12II is without doubt one of the best PSU's we've tested to date in the 300-500w arena. Not only does the unit manage excellent voltage stability at heavy loads; but it does it with excellent efficiency, low heat output and extremely low noise levels that even a ninja would be proud of!

The understated looks of the unit ensure that it will remain suitable for system builders and professionals, while the fully sleeved cables and black connectors are sure to appeal to the PC enthusiasts who want minimal cable clutter inside their windowed cases.

Coming in at around £45 over at CCL Computers, the SS-430GB is at the higher end of the price range for this wattage PSU when compared to models from other respectable manufacturers. However, if you put a high price on silence and performance, then this could well be the PSU for you.

Komplett - Recommended Retailer

The Good

- Good rail stability at full load.
- High efficiency recorded at almost 85%
- More silent than a ninja!
- Fully sleeved cables
- Easy-grip connectors.

The Medicore
- Price a tad higher than some other respectable 430w units.

The Bad
- None

OC3D Editors Chouce Award

Thanks to Seasonic for providing this unit for review. Discuss this review in our forums.