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

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.

The SeaSonic Focus GX-850 has its output specified for an ambient temperature of 50°C. Generally, PC power supply units (PSUs) are categorized based on their temperature ratings, with 40°C typically associated with low-end to entry-level mainstream units, and 50°C designated for quality mid-tier to high-performance products. The 50°C rating of the SeaSonic Focus GX-850 is unsurprising considering its target market and class, and a welcome upgrade over the previous Focus Plus series, which was rated at 40°C.

The performance of PC power supply units (PSUs) tends to diminish as the ambient temperature increases, with the extent of the degradation largely influenced by the design and quality of the unit in question. In the case of the SeaSonic Focus GX-850, the energy conversion efficiency experiences a marginal drop of just 0.4%, a figure that stands out favorably, especially for a quality 80Plus Gold unit. This minor decrement is consistent across the entire load spectrum, exhibiting no notable variance even under substantial load conditions. Such outcomes imply that the thermal stress exerted on the active components is remarkably low to mild, showcasing the design robustness of the SeaSonic Focus GX-850.

In contrast to some models, the fan within the SeaSonic Focus GX-850 initiates almost immediately upon powering on when the ambient temperature is high, reflecting a proactive approach to thermal management. The fan’s operation progressively escalates, reaching its zenith when the load approximates 80% of the unit’s rated capacity. This approach results in audible sound pressure figures even when the PSU is lightly loaded when the ambient temperature is very high, but, on the other hand, the proactive cooling strategy ensures a reliable operational landscape for the PSU.

As part of our testing, we also check output parameters are within specifications, as well as voltage ripple and line noise.

The SeaSonic Focus GX-850 exhibits exemplary electrical performance metrics. It features tight voltage regulation on all three of its primary voltage rails (12V, 5V, and 3.3V), maintaining a regulation of less than 0.4%. The unit also boasts a low voltage ripple on the 12V rail, with a maximum recorded ripple of 28mV. In addition to this, the 3.3V and 5V rails demonstrate effective filtering, as indicated by a maximum voltage ripple of 22mV. These figures indicate a well-engineered electrical design that adheres to stringent performance criteria for a product of this class.

As part of our standard testing, we test the primary protections of all PSUs we review (Over Current, Over Voltage, Over Power, and Short Circuit). All of the protections of the SeaSonic Focus GX-850 engaged normally and within our expected parameters without any significant deviations.

The SeaSonic Focus GX-850 emerges as a robust ATX 3.0-compliant competitor in the crowded market of power supply units. Its build quality is exemplary, with an elegant exterior, custom embossed chassis decorations, and the convenience of fully modular cables. The internal components do not disappoint either, boasting high-grade Japanese capacitors throughout. The self-manufacture by SeaSonic ensures a meticulously designed unit, showcasing a redesigned Focus series platform aimed at ATX 3.0 compliance. The compact and clean design further accentuates its aesthetic and functional appeal while ensuring compatibility with all ATX-compliant cases.

Performance-wise, the Focus GX-850 excels in power quality. It exhibits remarkable voltage filtering, keeping the voltage ripples restrained below 28 mV even under strenuous loads. The load regulation is tight, with a variance of less than 0.5% on all voltage rails, showcasing its ability to deliver stable power under different load scenarios. Additionally, it comfortably meets the 80Plus Gold efficiency requirements, marginally missing the 80Plus Platinum certification at maximum load.

On the thermal front, the unit fares well with commendable thermal performance characterized by relatively low operating temperatures, a feature attributable to its high efficiency. Despite its substantial power output, the PSU maintains a cool operation, vital for long-term reliability and optimal performance. The noise level is another aspect where the Focus GX-850 shines; it operates nearly silently at low loads and room temperature. Although the noise level ascends with increased load, it remains within a tolerable range for most users.

The value proposition of the Focus GX-850 is somewhat nuanced. SeaSonic has undeniably elevated the performance metrics in the new Focus GX series over the preceding Focus Plus units. But with a plethora of comparable products in the 80Plus Gold segment, there’s no shortage of competitors for the Focus GX. The good news is that, in the span of writing this article, we’ve already seen Amazon knock $25 off of the price of the PSU, bringing it down to what is (this morning) a cool $124. At that price, the superior build quality and a reassuring 10-year warranty really make the Focus GX shine over other Gold PSUs – and even priced a bit higher, there would still be a good argument for it.

Ultimately, the SeaSonic Focus GX-850 ATX 3.0 is a formidable contender for those seeking a blend of quality, performance, and reliability, living up to the reputation that SeaSonic has come to be known for.