Seasonic X-Series KM3 650 W Power Supply Review

Conclusions

The new X-Series KM3 650 W is another flawless power supply from Seasonic, targeted to users who demand only “the best.” Its efficiency surpassed the numbers promised by the 80 Plus Gold certification, noise and ripple levels were very low, and voltage regulation was outstanding, with the main positive voltages (+12 V, +5 V, and +3.3 V) within 1% of their nominal values. The ATX12V specification allows a 5% deviation, and we usually consider units with 3% voltage regulation as “flawless.”

Other highlights of the Seasonic X-Series KM3 650 W include the fully modular cabling system and the semi-passive mode of operation, where you can configure the power supply to turn on its fan only when you pull above 30% of its labeled wattage, and at low speed between 30% and 50% load, thereby making the power supply silent when the computer is not demanding a lot of power.

Costing USD 130, it is more expensive than the other 650 W power supplies around. However, we think the peace of mind of using a flawless power supply is worth every cent.