Seasonic SS-300FS Active PFC PSU

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June 5, 2002 -- by Mike Chin

Products: Seasonic SS300-FS 300W Power Supply Units with Active PFC
Date: June 4, 2002
Manufacturer: Sea Sonic Electronics
Supplier: Sea Sonic Electronics USA

The Seasonic SS-300FS has the distinction of being the first product sample voluntarily submitted for review in Silent PC Review. Until now, it is we who have approached them. As a new site with no track record, sometimes we have had to beg, cajole and plead for review samples. We don't mind; this is to be expected, and such experience may be good for humility, for the soul. Naturally, we are pleased that Seasonic approached us. It feels like progress.

There are good reasons why Sea Sonic Electronics submitted their product for review in Silent PC Review:

  • We have the right audience. The SS-300FS is claimed to be a quiet product. This is exactly the kind of product we want to review and that our community wants to hear about.
  • They need the exposure. Seasonic is only just beginning to establish a presence in North America, which a big chunk of our audience. A review that focuses especially on their product's claimed strength would help their marketing.

The fact is Seasonic was formed before the birth of the PC, all the back in 1975. Their headquarters are now in Taiwan, where production facilities have the capacity to churn out 850,000 power supply units a month. Yup, no missed decimal points there: 850 thousand. This company is no baby.


The review sample came in a nice colorful box suitable for retail display. Not that we really care but it does show a certain level of attention to detail. The MSRP is US$65, fairly standard for a quality brand PSU of this power rating. A binder of information about Sea Sonic Electronics, 5 pages of detailed technical specifications and 7 pages explaining their S2FC fan control circuit was also provided. A nice touch for the reviewer. There are no instructions inside the box, just the SS-300FS PSU in plastic bubble-wrap.

The front panel sports the usual AC jack, power switch and a chassis cutout grill for fan outflow. This last feature is never impressive. We all know that a wire frame grill causes much less wind turbulence and noise, and likely adds only pennies to the cost. Perhaps this review will show Seasonic that it matters to some consumers.

A 110V-to-220V switch is notable by its absence; the unit automatically adjusts for any AC voltage from 90V to 264V. This may not be a significant feature for users, who are unlikely to transport their PCs between 110V and 220V zones. However, it may help to save on production and distribution costs.

Cables are plentiful: aside from the usual ATX , legacy, and 12V (P4) connectors, there are 7 4-pin Molex connectors for IDE devices and 2 for floppy drives. Cables are on the long side, but not as long as the Enermax PSU: 27" stretched for the IDE connector cables.

Specifications are available at Seasonic's web site in PDF format.

The efficiency rating is average: over 65% at full load on 110 VAC. DC output specifications are consistent with those for most quality 300W PSU.

DC Output

Ripple & Noise

Output Load Current

Combined Power














Under the cover, the SS-300FS has two reasonable sized heatsinks, and a tidy layout with a clean printed circuit board. It sports an ADDA brand fan, model AD0812HS-A70GL, rated at 0.25A, 12VDC. Adda has a reputation for making good quality fans. Trying this one quickly in free air revealed a fairly smooth even sound unmarred by ticking, clicking or other annoyances. At 12V, it is quite loud. At 5V, fairly quiet but with a slightly buzzy or whirring quality -- evidence of some bearing noise. According to ADDA's website, it is rated for 38 CFM, 34 dBA and spins at a maximum of 3,000 RPM. The fan is thermally-controlled by a thermistor clamped to one of the 2 heatsinks.

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