The SeaSonic Focus GX-850 ATX 3.0 PSU Review: Cool, Quiet, and Robust

Cold Test Results (~25°C Ambient Temperature)

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M 40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs - 2014 Pipeline post.

The SeaSonic Focus GX-850 exhibits particularly high energy conversion efficiency for an 80Plus Gold unit, narrowly missing the 80Plus Platinum certification for an input voltage of 115 VAC due to a slight dip at maximum load. Its efficiency with an input voltage of 230 VAC is also very high for an 80Plus Gold-certified unit, with an average efficiency across the nominal loading range of 92%. The average efficiency drops to 90.1% if the input voltage is 115 VAC, a very significant 1.9% drop, yet it remains very high for an 80Plus Gold-certified product.

In its default setting on the SeaSonic Focus GX-850, the thermal control operates in a semi-fanless mode, which signifies that the fan activation is contingent on the requisite cooling demand. With the unit operating at room temperature, the fan activates when the load is greater than 240 Watts. This approach, while fostering quieter operation under low to moderate loads, leads to a relative elevation in the internal temperatures of the PSU prior to fan engagement. That, however, is virtually insignificant, as the fan engages long before the temperatures reach threatening figures.

As mentioned above, the SeaSonic Focus GX-850 has its fan remaining inactive until the load surpasses a defined wattage. Once activated, the fan operates at a virtually inaudible sound pressure level until the load extends beyond half the unit’s rated capacity. Beyond this load threshold, the thermal controller progressively augments the fan speed to adeptly manage the escalating cooling demands of the PSU, thereby ensuring a harmonious balance between operational efficiency, thermal management, and acoustic comfort.