Pros, Cons And Final Verdict
The SX550 is a budget-oriented PSU that, according to SilverStone, addresses mostly system integrators that need lower-priced parts. In order to make the SX550 more affordable (by SFX standards), FSP, which manufactures the power supply, employs an ACRF topology. This turns out to be the SX550's greatest weakness. Though it utilizes less expensive parts compared to half-bridge and full-bridge topologies, it simply cannot match their performance. As a result, you get lower efficiency, especially under higher loads, and a poor-performing +12V rail in transient loads. Conversely, this design proves to have better ripple suppression than the Enhance and Sirtec platforms that the SX600-G and SX500-LG models use. On top of that, FSP's platform has a higher temperature rating, at 50 ºC.
FSP is a large manufacturer with lots of experience in this field, that's for sure. But we strongly believe that its ACRF implementations need more work in order to be competitive. The SX550's pair of bridge rectifiers look weak, since they aren't bolted onto a heat sink. Moreover, the over-power protection's triggering point is set too high, allowing the +12V rail to fall close to 11 V when the PSU is overloaded. Meanwhile, ripple on the minor rails goes sky high. To add insult to injury, OPP doesn't activate even when the PSU is clearly taxed with close to 630 W, and according to the official specs, under-voltage protection isn't provided (though the ATX spec doesn't require it).
The lack of modular cables is a big let-down for us, and we don't like the fact that the fixed cables aren't sleeved all the way back into the chassis. The lack of a grommet around the cable exit hole doesn't look good either. If the SX550 was priced around $80, we would probably overlook some of its deficiencies. Priced at $95, however, it's dangerously close to Corsair's top-notch SF600, which offers much higher performance along with modular cabling and a larger fan that promises quieter operation. Given the minor price difference between Corsair's offering and the SX550, SilverStone's solution isn't very attractive. The company should adjust its price if it wants to make it more competitive. The provided warranty should be also increased to at least five years, given that the competition provides seven-year coverage.
The SFX landscape changed dramatically once Corsair got involved. SilverStone doesn't play alone any more, and it needs to adapt to this new reality if it wants to maintain market share. The SX550 needs several performance improvements or a significant price cut before we deem it worthy of your attention.
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