Corsair's AX1000 offers tight load regulation on all of its rails, amazing ripple suppression, and crazy-high efficiency levels. Its transient response is impressive, so we're not surprised that it takes the lead from Seasonic's 1000W 80 PLUS Platinum- and Titanium-rated models (even though they're built using the same platform with slight modifications).
The AX1000's hold-up time isn't as long as Seasonic's PSUs, but it still exceeds 17ms, satisfying the ATX specification's requirements. Where Corsair trails Seasonic is in our noise measurements: the 1kW Titanium Seasonic Prime achieves a much lower overall noise output. Corsair's AX1000 isn't noisy though; our average measurements remained under 25 dB(A), which is great given its 1000W of capacity.
We'll say it again: Corsair's AX1000, along with the 80 PLUS Platinum- and Titanium-rated Seasonic Prime models, are currently the best 1kW PSUs that money can buy. It's nice to see the company's legendary AX series make a strong comeback. For a while there, the AX family lived in the shadow of Corsair's digital AXi line-up.
Seasonic is among the best PSU OEMs and Corsair is one of the strongest brands nowadays, so a partnership between was bound to be successful. Although we live in a digital era, analog platforms still dominate the PSU market. We're looking forward to fully digital platforms from Seasonic and Corsair, but it's easier to wait with high-performance designs like the AX1000 to tide us over.
With a $280 (£220) price tag, the AX1000 certainly isn't cheap. But it offers the highest possible performance, quiet operation, and relatively compact dimensions, given a 172mm depth measurement. Smaller 1kW power supplies exist, but none of them can match the AX1000's performance.
The selectable semi-passive mode is a big advantage if you plan to use this unit with its fan facing downwards or sideways. We're hoping that Seasonic goes fully digital with its fan control circuit in the near future. An MCU with advanced PWM control would obviate the need for semi-passive operation, which puts a lot of stress on FDB fans during their start-up phase, causing lubricant to go all the way up the bearing.
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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.