The new Straight Power 11 Platinum line focuses more on noise output than performance, which is expected from be quiet! It's not that the overall performance is low, but we expected to see a larger difference with the previous model, given the platform upgrades that boosted efficiency. Unfortunately, the new unit has a downgraded 5VSB circuit with notably lower efficiency than the previous model, and the Vampire power levels are high with both voltage inputs.
The parts that FSP used in this platform are of high quality, especially the bulk caps of the APFC converter. It is the first time that we see a 5000h lifetime bulk cap in a desktop PSU, with the majority of units using 2000h bulk caps. It is also nice to see 16AWG gauges used on the ATX and EPS connectors of a 550W PSU, and the cable length is fully satisfactory. Moreover, this is one of the few power supplies that has an adequate distance between all of its peripheral connectors (both SATA and 4-pin Molex ones). Usually, the distance between those connectors is 100-120mm, leading to compatibility issues even with mid-size cases.
The FSP platform that the Straight Power 11 Platinum 550W uses has potential, but we noticed several issues that not only affect the overall performance but can also bring trouble in extreme scenarios. We are referring to the protection features, where the OCP triggering points on all rails are set too high. The same goes for the over-power protection, which shuts down the PSU at around 793W.
Under normal operating temperatures, the PSU might survive such high loads, but at higher temperatures (>40 degrees Celsius), this could lead to its destruction. The competition is fierce in this Wattage and price range, with the Fractal Design Ion+ 560P offering higher overall performance, ultra-flexible cables, and equally quiet operation. The Seasonic Focus Platinum 550W and the Corsair RM550x units also achieve notably better performance and feature silent operation.
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Disclaimer: Aris Mpitziopoulos is Tom's Hardware's PSU reviewer. He is also the Chief Testing Engineer of Cybenetics and developed the Cybenetics certification methodologies apart from his role on Tom's Hardware. Neither Tom's Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.