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Final Analysis
The following video footage shows the unboxing and internals of SSR-850FX.
Seasonic offers high performance to the masses with its new Focus line, and it scores big points with aggressive pricing. Right now, you'll find lower-efficiency competitors with inferior build quality and fewer features at the same price points as Seasonic's Focus Plus Gold models. That makes picking these PSUs a no-brainer.
The SSR-850FX is the Focus Plus Gold's flagship, featuring excellent load regulation, great ripple suppression, a long hold-up time, quiet operation under low loads, and a good transient response at +12V. Its most notable weaknesses are the minor rails' average transient response and the 5VSB rail's middling efficiency. It would be also nice if Seasonic used a regulator IC with over-current protection for the -12V rail. Otherwise, if you heavily overload that rail, the PSU will break down. Fortunately, most components don't use -12V any more. Still, in an advanced platform like the one Seasonic built, we want to see every possible protection feature enabled.
In addition to its relatively affordable price tag, the SSR-850FX boasts particularly compact dimensions for an 850W PSU. Moreover, its six PCIe and two EPS connectors ensure compatibility with high-end PCs. It used to be that enthusiasts didn't have to care how many EPS connectors their PSUs included. But today's high-end CPUs often require more power than one EPS connector can deliver, leading to major compatibility issues.
Seasonic's semi-passive mode should please builders specifically looking for quiet operation. Of course, when you push this PSU hard enough in a warm environment, that 120mm fan will make its presence felt. That shouldn't happen often; after all, 850W of output is a lot, even for a high-end system. If you don't want the fan to spin down under light loads, you do have the option of turning the SSR-850FX's semi-passive mode off. We always appreciate when manufacturers give you this choice, rather than forcing one configuration or another.
Simply put, the SSR-850FX is a great bargain at its current price. At the time of writing, EVGA's notably inferior 850 B3 costs just as much, yet offers much lower performance, achieves worse efficiency, exhibits questionable build quality, and is backed by half of the Focus PSU's warranty coverage. We don't know how, but Seasonic is keeping the price low on these models, creating huge problems for the competition. That's good for educated enthusiasts, though. Other manufacturers will have to drop their prices in order to battle Seasonic's Focus family.
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