Seasonic S12-500 & S12-600 Power Supplies

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May 22, 2005 by Mike Chin with Devon Cooke

*POSTSCRIPT added Oct. 22, 2005*

Seasonic S12-500 ATX Power Supply
Model SS-500HT Active PFC F3

Seasonic S12-600 ATX Power Supply
Model SS-600HT Active PFC F3
S12-500: US$130
S12-600: US$160

Seasonic is one of the longest-established makers of computer power supplies, and their products have consistently won respect from SPCR. The S12-430 we reviewed around two months ago turned out to be the one of most efficient fan-cooled PSU encountered, and also the quietest by a pretty big margin. Early production samples of the highest powered models in the S12 line, the 500 and 600, were also on hand at the time of the review, but Seasonic requested that we delay the review until newer samples were made available. A production change in the fan was coming, and this would affect the entire S12 line.

The Seasonic S12-500 and S12-600 differ from the lower powered S12 models more than just by power rating. These models actually use a different circuit design than the lower power models. Their model number, SS-500/600HT Active PFC F3, is different from the rest of the S12 line, SS-330/380/430HB Active PFC F3. The latter models feature upgraded variants of the circuit design used in the now-discontinued Super Tornado, while the 500 and 600 are entirely new. There is a third model, SS-400HT Active PFC F3, that logically belongs with the S12-500 and S12-600, but for whatever reasons, it appears to be unavailable for the retail market at this time.


The SS-xxxHT Active PFC F3 models have all been 80 PLUS certified. Regular readers of SPCR (and dedicated observers of the power supply scene) will know about 80 PLUS. SPCR provided news coverage about this initiative to promote the use of efficient power supplies in computers. There was also related discussion on page three of the article, A New Energy Star.

80 PLUS is described as "a national buy-down program for desktop computers and desktop-derived servers that contain highly efficient power supplies." The program invites submissions of PSUs, which are tested, and if the units pass, they become 80 PLUS approved. The test is quite tough: It calls for 80% or better efficiency at 20%, 50% and 100% of a PSU's rated power output. When a system integrator uses any 80 PLUS certified PSUs in systems, they can receive rebates through the 80 PLUS program, ostensibly to offset the initial higher cost of these highly efficient PSUs. You can check out all the details of the program, administered by Ecos Consulting, a company that "only undertakes projects that make a positive environmental impact", at the 80 PLUS web site.

The Seasonic SS-400HT APFC F3 was the first PSU to be approved by the 80 PLUS program. There are now four Seasonic PSU models on the approved products list. At time of posting, three other brands each feature a model on the an 80 PLUS approved PSU list.

What all this means to the end user is that the S12-500 and S12-600 should be >80% efficient at all power loads above 100W and 125W respectively. In SPCR's test rig, the S12-430 achieved the requisite >80% efficiency between 90W and 250W load but fell shy of it at maximum load. The 500 and 600 shouild fare better.

August 3, 2005

It came to our attention recently that the S12-500 and S12-600 are NOT 80 Plus approved, as thought previously. Seasonic's 80 Plus approved models are special OEM variants of the SS-400HT, SS-500HT and SS-600HT. The S12-500 / 600 have the same basic design, mechanically and electronically, but with longer output cables and the black paint finish, along with the box, manual and other accessories. The S12-500 and S12-600 are best viewed as variants of the SS-xxxHT OEM line. The 80 Plus approved SS-400HT, SS-500HT and SS-600HT models are OEM variants that come with special 80 Plus label.

This does not change the rest of the contents of our review nor our opinion of the S12-500/600.


The retail boxes for the 500 and 600 have new sticker labels that suggest changes and improvements.

New stickers on the box.

The blue orca image is now flanked by two prominent labels on the top left corner:

Two new labels on the S12-500 and S12-600 box.

It turns out that the top larger sticker applies to all of the S12 line:

120mm Double Ball Bearing Fan - It's not clear exactly what type of ball bearing was used in the previous Yate Loon model fans that came in these S12s, but it must have been different for this point to be made. Seasonic states that the change was made in order to reduce rejects on the production line and to improve consistency.

Long-lived Aluminum Electrolytic Capacitor - Apparently, higher quality Japanese aluminum electrolytic capacitors are used for greater reliability and stable performance. More common China-made capacitors must have been used before, as is typical of most PSUs. There have been incidents of motherboard and PSU brands being affected by leaking capcitors sourced from China starting from ~2 years ago.

The second smaller sticker applies only to the S12-500/600:

Support SLI - PCI-Express X2 - Two 6-pin connectors with sufficient current capacity for PCI-E & SLI systems are provided. This is to ensure gamers get all the bang they need. Only the 500 and 600 are so equipped because they're the models deemed to be high enough power capacity to handle SLI.

A news release detailing these improvements can be found at Seasonic's web site.

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