Seasonic Focus SGX 650W SFX-L PSU Review: Reliable Power, Tiny Form Factor

Tom's Hardware Verdict

Small and powerful, the Seasonic SSR-650SGX achieves good performance and backs it up with a long warranty and plenty of features.


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    Full power at 46°C

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    Fair price

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    Good performance

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    High build quality

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    Fully modular

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    4x PCIe connectors

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    ten-year warranty


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    The fan profile aggressive at high loads

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    Not so efficient 5VSB rail

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    Single EPS connector

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Specifications and Part Analysis

The Seasonic Focus SGX 650W offers high overall performance and quiet operation at light and medium loads, of up to 340W. The competition in the small form factor SFX-L category hasn't been heated up yet and we are still waiting for Super Flower to release its highly anticipating small factor platform. Nevertheless, there are still some worthy opponents which belong to the smaller, in dimensions, SFX category with the Corsair SF600 having identical performance with the SSR-650SGX but plenty of noise output with high loads on the minor rails. If you are out for an SFX-L unit with 650W capacity and a fair price ($122 / £139), the SSR-650SGX should be among the top places in your list. Another strong advantage of this product is the ten-year warranty, which is the longest in this category.

Seasonic has finally entered the small form factor PSU market with its new SGX line, which currently consists of two models with 500W and 650W capacities. Both of them follow the SFX-L form factor and target users that need a good power supply but don't want to spend a fortune to get it. Usually the smaller a PSU the higher its price, so to be more competitive, Seasonic didn't equip the SGX with exotic features, like ETA-A+ or 80 PLUS Titanium/Platinum efficiency, which would significantly affect the production cost.

In this review we will take a look at the SSR-650SGX which is the strongest of the line with 650W max power, as its model number implies. This is a fully modular unit with a single +12V rail and a 120mm Fluid Dynamic Bearing fan. The impressive fact in this product is the ten-year warranty. Currently no other SFX-L or SFX unit is covered by such a long warranty, with Corsair's and EVGA's high-end SFX offerings being at seven-years. Personally I am not a fan of huge warranty periods since on the long run they can create problems not only to the brands that offer them but to the consumers as well, in case the RMA cost gets increased (hence this cost will have to be moved to the consumers somehow). Nonetheless, known brands like Seasonic, Corsair and EVGA wouldn't offer such long warranties, if they weren't extra sure that their products can outlive them.


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Manufacturer (OEM)Seasonic
Max. DC Output650W
Efficiency80 PLUS Gold, ETA-A (88-91%)
NoiseLAMBDA-S+ (35-40 dB[A])
Modular✓ (Fully)
Intel C6/C7 Power State Support
Operating Temperature (Continuous Full Load)0 - 50°C
Over Voltage Protection
Under Voltage Protection
Over Power Protection
Over Current (+12V) Protection
Over Temperature Protection
Short Circuit Protection
Surge Protection
Inrush Current Protection
Fan Failure Protection
No Load Operation
Cooling120mm Fluid Dynamic Bearing Fan (S1201512HB)
Semi-Passive Operation
Dimensions (W x H x D)128 x 66 x 128mm
Weight1.15 kg (2.54 lb)
Form FactorSFX-L, EPS 2.92
Warranty10 Years

Power Specifications

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Max. PowerAmps20205430.3
Total Max. Power (W)650

Cables & Connectors

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Modular Cables
DescriptionCable CountConnector Count (Total)GaugeIn Cable Capacitors
ATX connector 20+4 pin (360mm)1118AWGNo
4+4 pin EPS12V (400mm)1118AWGNo
6+2 pin PCIe (400mm+100mm) 2418AWGNo
SATA (300mm+200mm+100mm)2618AWGNo
4 pin Molex (300mm+200mm+200mm)1318AWGNo
AC Power Cord (1370mm) - C13 coupler1118AWG-

This is a fully modular power supply. The number of PCIe connectors is adequate, given the 650W capacity, but the single EPS can create compatibility problems with some high-end mainboards. Ideally there should be two EPS connectors.

All cables are short since this unit is destined for a small chassis, but the distance between the peripheral connectors is large enough to cover all usage scenarios. Finally, it is nice to see clean, from in-line caps, cables since those caps make them bulky, hence cable rooting/management tasks become harder.

Component Analysis

We strongly encourage you to a look at our PSUs 101 article, which provides valuable information about PSUs and their operation, allowing you to better understand the components we're about to discuss.

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General Data
Manufacturer (OEM)Seasonic
PCB TypeDouble Sided
Primary Side
Transient Filter4x Y caps, 2x X caps, 2x CM chokes, 1x MOV
Inrush ProtectionNTC Thermistor & Relay
Bridge Rectifier(s)1x
APFC MOSFETS2x Champion GPT18N50D (500V, 18A @ 150°C, 0.27Ohm)
APFC Boost Diode1x STMicroelectronics STTH8S06D (600V, 8A @ 150°C)
Hold-up Cap(s)1x Nichicon (400V, 470uF, 2000h @ 105°C, CE, GG)
Main Switchers2x Infineon IPP50R190CE (550V, 15.7A @ 100°C, 0.19Ohm)
Combo APFC/PWM ControllerChampion CM6500UN
Resonant ControllersChampion CM6901T6X
TopologyPrimary side: Half-Bridge & LLC converter Secondary side: Synchronous Rectification & DC-DC converters
Secondary Side
+12V MOSFETS4x Nexperia PSMN1R8-40YLC (40V, 100A @ 25°C, 1.8mOhm)
5V & 3.3V2x DC-DC converters
Filtering CapacitorsElectrolytics: 1x Rubycon (3000h - 6000h @ 105°C, YXG),1x Nichicon (2200uF, 16V @ 105°C), 9x Nippon Chemi-Con (105°C, W) Polymers: 13x FPCAP, 4x Nippon Chemi-Con
Supervisor ICWeltrend WT7527V (OVP, UVP, OCP, SCP, PG)
Fan ModelGlobe Fan S1201512HB (120mm, 12V, 0.45A, Fluid Dynamic Bearing Fan)
5VSB Circuit
Standby PWM ControllerExcelliance EM8569C
RectifierMBR1045ULPS (45V, 10A @ 90°C)

This is a new Seasonic platform featuring a half-bridge topology on the primary side which is enhanced by an LLC resonant converter, for restricted switching losses. On the secondary side, a synchronous rectification scheme is utilized for the +12V rail, while the minor rails are generated by a couple of DC-DC converters. The latter are hosted in the same PCB.

The quality of the parts that Seasonic uses is top-notch. All filtering caps are provided by Japanese manufacturers (Rubycon, Chemi-Con, Nichicon and FPCAP) and besides electrolytic caps, a large number of polymers is also used. Lastly, the cooling fan measures 120mm; it is provided by Globe fan and uses a fluid dynamic bearing which has a long lifetime.

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Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.