Seasonic, a veteran in power supply technology, is renowned for its commitment to high-quality PC hardware, particularly in the power supply unit (PSU) sector. Seasonic’s long-standing reputation is built on delivering reliable and efficient products tailored for a wide array of users, from high-demanding professionals to gaming enthusiasts. Known for designing and manufacturing its own platforms, Seasonic sets itself apart by focusing on component quality and performance, making the brand a staple for those who prioritize durability and stability in their systems.
In this review, we examine the Focus GX ATX 3, currently $189 in the U.S. and the latest in Seasonic’s widely-recognized Focus GX series. This 4th revision brings the new “OptiSink” design that offers improved thermal performance and enhanced efficiency, along with ATX 3.1 and PCIe 5.1 compliance. The unit that we tested is rated at 1000W @ 50°C and has an 80Plus Gold certification, appealing to users looking for a highly reliable, balanced offering with substantial power and the efficiency to compete with the best power supplies on the market.
Specifications and Design
| RAIL | +3.3V | +5V | +12V | +5Vsb | -12V |
| MAX OUTPUT | 25A | 25A | 83A | 3A | 0.3A |
| Row 2 – Cell 0 | 125W | Row 2 – Cell 2 | 996W | 15W | 3.6W |
| TOTAL | 1000W | Row 3 – Cell 2 | Row 3 – Cell 3 | Row 3 – Cell 4 | Row 3 – Cell 5 |
| AC INPUT | 100 – 240 VAC, 50 – 60 Hz | Row 4 – Cell 2 | Row 4 – Cell 3 | Row 4 – Cell 4 | Row 4 – Cell 5 |
| PRICE | $190 | Row 5 – Cell 2 | Row 5 – Cell 3 | Row 5 – Cell 4 | Row 5 – Cell 5 |
In the Box
The Seasonic Focus GX ATX 3 comes in robust packaging, featuring the black-and-gold aesthetic typically used by the company for the Focus series. The PSU itself is securely encased in a nylon pouch and protected by dense foam inserts for safe transit.
The company provides a comprehensive bundle of essentials, including mounting screws, an AC power cable, a jump-starting connector for testing, cable ties, and three quality cable straps, catering well to users who value a more complete installation kit.
The Focus GX ATX 3 includes all-black, individually sleeved cables, designed for flexibility and ease of management. This PSU comes with one 600W 12+4 pin PCIe connector, along with three 6+2 pin PCI Express connectors – a fairly conservative setup for the rated output of the unit.
| Connector type | Hardwired | Modular |
|---|---|---|
| ATX 24 Pin | – | 1 |
| EPS 4+4 Pin | – | 2 |
| EPS 8 Pin | – | – |
| PCI-E 5.0 | – | 1 |
| PCI-E 8 Pin | – | 3 |
| SATA | – | 8 |
| Molex | – | 3 |
| Floppy | – | – |
External Appearance
The external appearance of the Seasonic Focus GX ATX 3 has a premium, understated look. The PSU is encased in a satin black chassis with a smooth, high-quality finish. Seasonic added decorative embossments on the chassis’s sides, which provide a slight texture and break up the otherwise minimalist aesthetic. Both sides and the front of the PSU display the Seasonic and Focus GX branding.
The unit adheres to the ATX standard length of 140mm, making it compact enough to fit into any ATX-compliant case and leaving space for optimal airflow in tighter builds. Although 140 mm long units are typically limited to 120 mm fans, Seasonic tweaked the chassis to force a 135 mm fan to fit. The fan grille design is integrated directly into the chassis, forming a unique visual pattern.
On the rear panel, we find the standard AC input socket, an on/off power switch, and a hybrid fan mode button. Turning off the hybrid fan mode will force the fan to start regardless of the load but it does not override the thermal control of the fan, meaning that it would still be rotating at minimal speeds when the load is low. The front panel is where the modular cable connectors are located, with a subtle legend to guide users during installation.
Internal Design
The Seasonic Focus GX ATX 3 is equipped with a 135mm Hong Hua HA13525H12F-X fan featuring a fluid dynamic bearing (FDB), known for balancing durability and low-noise performance. By default, the fan is only engaging when necessary, thanks to its zero-RPM mode, which aids in reducing both operational noise and component wear over time.
As a fully in-house platform designed by Seasonic, the Focus GX ATX 3 series integrates Seasonic’s proprietary OptiSink design. OptiSink places the majority of heat-generating components on a dedicated daughterboard before the main transformer, reducing the space needed for heatsinks. This approach aids in heat dissipation and reduces the PSU’s overall footprint.
The input filtering stage includes four Y capacitors, two X capacitors, and two inductors, a typical and effective filtering scheme. The Active Power Factor Correction (APFC) stage features two Alpha & Omega B125A60L MOSFETs and one high-quality Nippon Chemi-Con 820 μF capacitor. The active components of APFC circuitry are located on the OptiSink PCB. The primary inversion stage is also located on the OptiSink PCB, comprising four Alpha & Omega B190A60C MOSFETs that form a standard full-bridge LLC setup.
On the secondary side, six Nexperia MOSFETs, located right after the main transformer in between two simple but tall heatsinks, generate the primary 12V line. DC-to-DC circuitry on a daughterboard at the edge of the unit produces the 3.3V and 5V lines. The secondary capacitors are all sourced from reputable Japanese manufacturers like Nichicon, Rubycon, and Nippon Chemi-Con.
Cold Test Results
Cold Test Results (25°C Ambient)
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.
During cold testing, the Seasonic Focus GX ATX 3 consistently meets the 80Plus Gold certification requirements across different input voltages. With a 115 VAC input, it achieves an average nominal load efficiency of 89.8%, which increases to 92.1% at 230 VAC. Efficiency peaks around 40% load, a little sooner than typically expected, and the unit maintains reliable efficiency throughout the nominal load range (10-100%). Efficiency at very low loads is also acceptable, though it could be improved further.
The fan in the Focus GX ATX 3 starts operating once the load exceeds 450 watts, running at a low speed up to approximately 700 watts. The fan becomes audible as the load exceeds 700 watts but never reaches its maximum speed, not even if the unit is left at maximum load for a prolonged period of time. The unit’s internal temperatures are relatively low throughout room temperature testing.
Hot Test Results
Hot Test Results (~45°C Ambient)
During hot testing, the Seasonic Focus GX ATX 3 experiences a measurable but unsurprising decrease in efficiency. The unit averages 88.9% efficiency at 115 VAC and 91.2% at 230 VAC, about 0.9% lower than the 89.8% and 92.1% observed during cold testing. This decrease is expected in elevated temperatures and remains within acceptable performance limits, with the unit showing no indication of thermal stress.
In higher ambient temperatures, the fan in the Focus GX ATX 3 activates at a slightly lower load threshold than during cold testing, beginning operation as soon as the load exceeds approximately 250 watts. The fan speed then ramps up progressively with the load, though it again never reaches maximum speed, not even under full load. While the fan becomes audible at higher loads, it remains within a tolerable noise range for the most part of the load range.
Internal temperatures are very well-regulated given the high power output of the unit, staying within safe operating limits and not getting anywhere near the thresholds for over-temperature protection (OTP), indicating an exceptional balance between thermal and acoustics performance.
PSU Quality and Bottom Line
Power Supply Quality
The Seasonic Focus GX ATX 3 demonstrates strong electrical stability and power quality within its category. Voltage regulation is precise, with the 12V rail holding at 0.4%, the 5V rail at 0.6%, and the 3.3V rail at 0.5%. Ripple suppression is well-executed, with maximum ripple levels of 34 mV on the 12V rail, 20 mV on the 5V rail, and 20 mV on the 3.3V rail. Filtering has room for improvement but is by all means excellent for a PSU of this tier.
During our thorough assessment, we evaluate the essential protection features of every power supply unit we review, including Over Current Protection (OCP), Over Voltage Protection (OVP), Over Power Protection (OPP), and Short Circuit Protection (SCP). All protection mechanisms were activated and functioned correctly during testing.
The Focus GX’s OCP is set to engage at 136% for the 3.3V rail, 140% for the 5V rail, and 130% for the 12V rail, with an OPP setting of 132%, all of which are reasonable trigger points for an ATX 3.1-compliant unit.
| Load (Watts) | 201.91 W | Row 0 – Cell 2 | 504.56 W | Row 0 – Cell 4 | 754.85 W | Row 0 – Cell 6 | 1005.72 W | Row 0 – Cell 8 |
| Load (Percent) | 20.19% | Row 1 – Cell 2 | 50.46% | Row 1 – Cell 4 | 75.48% | Row 1 – Cell 6 | 100.57% | Row 1 – Cell 8 |
| Amperes | Volts | Amperes | Volts | Amperes | Volts | Amperes | Volts | |
| 3.3 V | $2 | $3 | $6 | $3 | $9 | 3.4 | 11.37 | 3.4 |
| 5 V | $2 | $5 | $6 | $5 | $9 | 5.08 | 11.37 | 5.07 |
| 12 V | 15.09 | 12.1 | 37.74 | 12.09 | 56.6 | 12.06 | 75.47 | 12.05 |
| Line | Regulation (20% to 100% load) |
Voltage Ripple (mV) | Row 0 – Cell 3 | Row 0 – Cell 4 | Row 0 – Cell 5 | Row 0 – Cell 6 | Row 0 – Cell 7 |
| Row 1 – Cell 0 | Row 1 – Cell 1 | 20% Load | 50% Load | 75% Load | 100% Load | CL1 12V |
CL2 3.3V + 5V |
| 3.3V | 0.50% | 16 | 12 | 16 | 20 | 18 | 14 |
| 5V | 0.55% | 18 | 12 | 18 | 20 | 18 | 16 |
| 12V | 0.40% | 20 | 18 | 24 | 34 | 30 | 20 |
Bottom Line
The Seasonic Focus GX ATX 3 presents itself as a high-quality, well-rounded PSU that combines good overall performance, long-term reliability, and modern features, making it a compelling choice for users with high demands.
With its 1000W output and 80Plus Gold certification, this unit delivers solid efficiency, consistently meeting the requirements across a wide range of input voltages. Its compliance with ATX 3.1 and PCIe 5.1 standards ensures compatibility with current top-tier and next-gen equipment, making it future-proof for demanding setups.
The standout aspect of the Focus GX ATX 3 undoubtedly is its exceptional build quality. It is built with premium components all-around and sports an immaculate assembly job. The highlight is the OptiSink design that helps with heat dissipation and reduces the overall size of the unit. According to Seasonic, the OptiSink design also minimizes manufacturing defects, ensuring better quality.
Performance-wise, the Focus GX ATX 3 does not set any records but shines through its balance. It achieves great average efficiency figures that rival Platinum-certified units, with a relatively small drop in efficiency during hot testing that implies exceptional resilience towards adverse operating conditions. The fan remains either off or relatively quiet across most of the load range, only becoming noticeable under high loads, all while internal temperatures are very well-managed. Voltage regulation is precise and ripple suppression is effective, ensuring clean and stable power.
Perhaps the only shortcoming of the Focus GX ATX 3 is the current retail price. Retailing at $189, the Focus GX ATX 3 is priced on the higher end of the spectrum. While it may be considered expensive for some, the cost is justified by its top-quality components, reliability, and balanced performance. For users prioritizing long-term durability, especially in high-demand systems, the Focus GX ATX 3 currently is a good investment.
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