Antec was smart to cooperate with Seasonic, utilizing the company's successful Focus platform and slapping its own brand on the design. The resulting HCG850 scores well overall. But Seasonic's equivalent Focus Plus Gold model fares even better thanks to a superior hold-up time. Although both PSUs are based on the same foundation, the SSR-850FX employs a different bulk capacitor in its APFC converter. Seasonic's bulk cap is a bit smaller than Antec's. However, it also seems to offer more capacity, given an almost 6ms-longer measurement. In the end, Antec's HCG850 still exceeds the ATX specification's requirements and its power-good signal is accurate, so we really can't complain.
The Seasonic Focus Plus Gold and Antec HCG families operate quietly under normal and moderate loads, despite their 120mm fans. Under tough conditions, though, both power supplies get pretty loud. We recorded an overall noise output close to 35 dB(A) for both models, while their direct competition, Corsair's RMx series, ducks in under 20 dB(A). In short, if you need an 850W PSU that stays quiet even when it's working hard, then avoid the HCG850. On the other hand, if you're not really worried about acoustics, but rather need compact dimensions, then the Focus platform is ideal. While we're pretty sure that a 135mm fan would have helped tame the noise measurements, Seasonic probably didn't want to create competition with some of its higher-end Prime Ultra models.
Antec's HCG850 does offer high performance in all of the disciplines we test. Its main shortcoming is the 3.3V rail's transient response. Normally, then, we'd have a lot of nice things to say about such a capable power supply available for $110. But we're faced with the rather serious problem of two catastrophic failures during our protection feature testing. One died after completing the over-power protection evaluation, and a second HCG850 stopped working after testing the 5VSB rail's over-current protection. We do expect the occasional untimely demise. After all, our benchmark suite is uncommonly grueling. Protection features are there for a reason, though. They should effectively protect the PSU from tasks that'd otherwise damage it. Clearly, this wasn't the case. A single failure might be chalked up to bad luck. Two failures in a row, however, suggest a more serious problem. We naturally let Antec know about our findings, and sent both samples back for diagnosis. Should we hear more, we'll update our review. For now, the HCG850's rating is low to warn Tom's Hardware readers away from it.
MORE: Best Power Supplies
MORE: All Power Supply Content
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, Purch Media, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.