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::>Power supplies > 2015 > 03 > Seasonic X-1250 (SS-1250XM2)

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PSU Seasonic X-1250: review and testing

Lately for testing we had many high power supply units manufactured by Sea Sonic Electronics. All of them have a very high performance and excellent consumer qualities, but in most cases they were intended for installation in conventional systems. And we would like to test the solutions for enthusiasts. And finally we have such an opportunity. Today for testing we have a model Seasonic X-1250 (Seasonic SS-1250XM2). Rated power of the power supply is 1250 W, which makes it the most efficient solution in a series of   Seasonic X.

Note that the Seasonic X-1250 also fell under the global updating campaign of upscale devices from Sea Sonic Electronics. And, judging by the new index (SS-1250XM2), it affected not only the cost of the power supply, but also major changes took place at the hardware level.

Seasonic X-1250 (SS-1250XM2)

The specs:


Seasonic X-1250

(Seasonic SS-1250XM2)



Rated capacity, W


12V channel capacity, W


+3,3V and +5V channel capacity, W


Q-ty of +12V lines


Outputs, А









+5VSB (stand-by power line)



10 (6+2-pin)

Support for technologies NVIDIA SLI / AMD CrossFireX




Efficiency, %


Certified 80 PLUS


Power factor, %


Method of Power Factor balancing


Input voltage, V

100 - 240

Frequency, Hz

50 - 60

Input current, А

7,5 - 15

Fan dimensions, mm

120 х 120 х 25

Fan speed controller

Yes (hybrid cooling system)

Noise level, dB


Support for energy saving states C6 / C7(Intel Haswell Ready)


Correspondence to environmental standards, electromagnetic safety and compatibility (EMI/EMC)




Dimension, mm

190 х 150 х 86


Power cord, fastening screws, modular cables, cable holders, straps with adhesive tape, manual, logo sticker 

Warranty, years


Producer website


Package and content

Seasonic X-1250 (SS-1250XM2)

Power supply Seasonic X-1250 comes in a cardboard box which provides protection against shocks and possible mechanical damages. The package is decorated in a traditional Seasonic X series style and a good informative content. Its ends have detailed characteristics of the device, and the back side contains a brief description of its major advantages.

Seasonic X-1250 (SS-1250XM2)

We offer to meet with them in more detail:

  • DC-to-DC - an advanced circuitry based on DC converters is used;
  • Seasonic Patented DC Connector Panel with Integrated Voltage Regulation Module - patented module design of inverter DC-DC, which can reduce the energy loss in the low-voltage side, to improve quality of installation and cooling elements, as well as to simplify the structure of the entire build;
  • Ultra Stable Voltage - excellent stability of output voltages (+ 12V channel has deviations in the range 0% ...+2% and on the lines +3.3V and the +5V within -1% ...+1%);
  • Dual Copper Bars - thicker field copper lines are used to reduce resistance to the current, which results in less loss of energy;
  • Highly Reliable 105°C Aluminum Electrolytic Capacitors, Conductive Polymer Aluminum Solid Capacitors - all nodes contain high-quality Japanese capacitors belonging to the high-temperature series;
  • 80 PLUS Gold Certified - a high level of efficiency compliant with standard 80 PLUS Gold;
  • Seasonic Hybrid Silent Fan Control S2FC & S3FC - availability of advanced hybrid cooling system, thanks to which the fan do not rotate at low loads;
  • Sanyo Denki San Ace Silent Fan - the use of high-quality fans based on ball bearings;
  • Gold High Current Terminal – presence of  gold sputtering on terminals for connecting components;
  • Multi-GPU - support configurations that include multiple graphics cards, combined in mode AMD CrossFireX or NVIDIA SLI;
  • 7 Years Warranty - 7 years warranty.

Without opening the box we can already see that this is a high quality device equipped with the best developments in the field of power supplies. Most of them are well known to our readers via the previous reviews of solutions of the series Seasonic X and Seasonic Platinum, but we would like to pay more attention to the one technology.

Seasonic X-1250 (SS-1250XM2)

We are talking about a hybrid cooling system, which undergone further modernization. This made it even more progressive on the part of fan speed control. Firstly we recall the main advantage of a hybrid cooling system over its standard counterpart. It means that until a certain temperature the fan does not rotate, and then its rotational speed is determined by heating of the internal components. And the better organized air circulation in the computer case, the later fans starts to rotate.

Compared with other solutions in a series of Seasonic X, here engineers improved the algorithm of this technology by adding a hysteresis band (20% - 30%). This innovation allows you to avoid the situation with constant on/off the fan at low loads. This should further improve the acoustic properties of the power supply, without affecting the efficiency of cooling, as well as extend the life of the fixed fan.

Seasonic X-1250 (SS-1250XM2)

Supplied set of model Seasonic X-1250 contains:

  • AC power cord;
  • screws to secure;
  • modular cables in a special bag;
  • holders to secure the wires;
  • reusable ties adhesive strip;
  • sticker with the logo of the company;
  •  manual

In addition to the traditional components, in the box we also found additional collars and ties with adhesive strip, which will be useful for accurate placement of wires. To store the cables there is a proprietary two-piece bag.


Seasonic X-1250 (SS-1250XM2)

Model Seasonic X-1250 looks more like a congener of "platinum" series (Seasonic Platinum 1200), except that the color of the fan grille. Instead, it became a golden gray. This arrangement the case, its size, configuration of the rear panel remained the same. Excellent build quality of the power supply unit also remained the same.

Seasonic X-1250 (SS-1250XM2)

Pay attention to the increased size of the device, which is 190 x 150 x 86 mm. Therefore, if you install Seasonic X-1250 at the bottom of the computer case the hole for the additional fan will be partially overlapped.

Seasonic X-1250 (SS-1250XM2)

Output cable system has completely modular configuration that fully corresponds to the concept of Sea Sonic Electronics of high-power units. This technical performance will make the process of components connection and routing of cables simple and convenient. The rear panel contains 15 connectors. Given that in most cases, each cable has several connectors, it will simultaneously connect incredible number of components. It is difficult to imagine a configuration in which it will be necessary to use all of them. Full list of connectors on the rear panel contains:

  • 18-pin and 10-pin («M/B») - to power the motherboard;
  • five 6-pin («Peripheral IDE/SATA») - to supply periphery
  • eight 8-pin («CPU/PCI-E») - for additional power processor and graphics card.

The upper right corner has a switch «Fan Control». In position «Hybrid» fan will operate as described in the previous section diagram. In the «Normal» it begins to rotate immediately after starting the PC, that is, even at minimum load. This version of the cooling system can be useful if Seasonic X-1250 is is planned to operate in an environment of high temperature. Such conditions may arise, for example, in a poorly blown case or on the overclocking stand.

Seasonic X-1250 (SS-1250XM2)

All wires have the form of strips except used for the motherboard powering. This makes them more flexible than traditional ones with braiding, and considerably facilitates the laying hidden in modern computer case.

Main power connectors have the following configuration: collapsible 20+4-pin ATX and two 8-pin ATX12V (one of which is also collapsible). In order to connect the graphics card there are ten PCIe connectors in the 6+2-pin version. Thus, Seasonic SS-1250XM2 is perfect for all types of high-performance configurations: gaming PCs, "farm" for mining or system for overclocking experiments.

We were pleased by configuration of cables for power supply of the periphery. Available connectors are enough to connect all kinds of storage devices, drives, fans and other devices that require SATA and PATA connectors. Therefore, besides the above described systems, Seasonic X-1250 is also suitable for a file server or client torrent.

Socket type


Cable length to socket (connectors), cm

Modular (detachable) cables

20+4-pin power socket ATX



4+4-pin power socket ATX12V



8-pin power socket ATX12V



two 6+2- pin power sockets PCIe



6+2-pin power socket PCIe



three sockets PATA



two sockets PATA



four sockets SATA



two sockets SATA



adapter PATA-FDD



Seasonic X-1250 (SS-1250XM2)

Now let's take a closer look at the technical characteristics of the power supply Seasonic SS-1250HM2. Its nominal power is 1250 W. Channel +12V is designed as a single line with a load capacity of up to 104 A. In other words, if necessary it will be possible to "remove" virtually 100% of the total power that is quite popular option today, especially when it comes to components acceleration. Lines +3.3V and +5V have a maximum total power of 150 W and are designed for a load of 25 A each. These characteristics will impose minimum restrictions and will be able to provide the user with complete flexibility in the choice of the PC configuration.

Model Seasonic X-1250 corresponds to the class of energy efficiency 80 PLUS Gold. Thus, for the voltage to 230 V at a load of 20%, 50% and 100% of the nominal power, this figure should not fall below 88%, 92% and 88% respectively.

Also do note a wide input voltage range (100 – 240 V), which eliminates the external voltage regulators in an unstable power supply.

Internal device

Seasonic X-1250 (SS-1250XM2)

In order to cool internal components 120mm 7-blade fan SANYO DENKI 9S1212H403 is applied. It is based on two ball bearings. Unfortunately, we could not find its complete specification. However, taking into account the fan power at the level of 4.68 W, we can say about its performance.



Bearing type

Dual Ball

Supply voltage, V


Current, A


Capacity, W


Maximum rotation speed, rpm


Air flow, CFM


Noise level, dB


Dimensions, mm

120 х 120 х 25

Seasonic X-1250 (SS-1250XM2)

The updating of family Seasonic X for model Seasonic X-1250 effected the change of platform. Now it is based on the most advanced proprietary development - circuit design, codenamed «Seasonic XP3», which is a further modernization of series Seasonic KM3. We have already seen it in the "platinum" solution Seasonic Platinum in 1200 and it made the most pleasant affect.

Seasonic X-1250 (SS-1250XM2)

Seasonic X-1250 (SS-1250XM2)

The input of the high-voltage side has an EMI-filter for smoothing the high-frequency noise emitted by the power supply. Also it bears the function of lightning protection. Implementation of the input filter is at the highest level, as evidenced by the presence of all necessary components (three X- and six Y-capacitors, three chokes and varistor), as well as a careful approach to isolation and shielding.

The input diode bridge consists of two 25-ampere assemblies GBJ2506 and is cooled by a separate aluminum radiator.

Seasonic X-1250 (SS-1250XM2)

Behind them you can find active unit power factor correction (APFC) with the power unit in the form of three field-effect transistors Infineon 5R140P and Schottky diode ROHM SCS110AG. Since till a certain load Seasonic X-1250 can operate with inactive fan, the cooling is a high level.

Seasonic X-1250 (SS-1250XM2)

High-voltage capacitors are represented by three elements (390 uF x 420 V, operating temperature up to 105°C) produced by the Japanese company Hitachi, which guarantees their high quality and long service life even under constant heavy loads. Since they are connected in parallel, their total capacity is 1170 uF. And this is an excellent figure for a 1200 W unit.

Seasonic X-1250 (SS-1250XM2)

The main converter is built on a highly resonant circuit with a full bridge. Its keys are the four transistors Infineon 5R250P, operating in pairs under the control of the PWM controller CM6901. The last is attached on a separate small circuit board near the high-voltage capacitors. Chip NCP1654 responsible for the APFC operation, together with bunch also is a node. This modular approach greatly simplifies the design of power supplies, their building and maintainability. In addition, the use of universal nodes reduce the end cost of production, which can be seen on the example of the updated revision of the Seasonic X series and Seasonic Platinum.

Seasonic X-1250 (SS-1250XM2)

Low-part of model Seasonic X-1250 is a synchronous rectifier: it has one powerful +12V line that provides voltage +3.3V and +5V. That is, this is the same principle as in younger "gold" models, but the configuration of the node was changed. In particular, here you won’t find a separate board with the transistors to form the channel +12V, thus freeing up space for the installation of a massive radiator.

Seasonic X-1250 (SS-1250XM2)

The power elements (Infineon 027N04LS 8 pieces) "moved" on the back side of the PCB. Part of the heat is transferred onto the above-mentioned radiator.

Seasonic X-1250 (SS-1250XM2)

The rest of the body is moved to the power supply through thermal pad, thereby turning it into a kind of a big heatsink. It is a pretty good technical solution that will allow to avoid overheating of transistors during Seasonic X-1250 operation in case of inactive fan.

Seasonic X-1250 (SS-1250XM2)

Seasonic X-1250 (SS-1250XM2)

Board with voltage converters +3.3V and +5V is another clear example of the use of modular power supply from the Sea Sonic Electronics. In addition to the power unit (six transistors Infineon BSC0906NS, running by PWM controller APW7159), also here are components of the filters and a part of modular connectors. This approach eliminates the underwater part, thereby minimizing energy losses and noise on the outputs Seasonic SS-1250XM2. By the way, exactly the same board was used in "platinum" model Seasonic Platinum 1200.

Seasonic X-1250 (SS-1250XM2)

Seasonic X-1250 (SS-1250XM2)

The ripple smoothing over the lines +3.3V and +5V is provided by solid capacitors with the characteristics of the 560 uF x 6.3 V. The channel +12V has elements with a solid (330 uF x 16 V) and a liquid electrolyte (1000 uF x 16 V). In all cases, the manufacturer is an authoritative Japanese company Nippon Chemi-Con. Note that these capacitors belong to the high temperature series (105°C).

Seasonic X-1250 (SS-1250XM2)

According to the technical specifications, model Seasonic X-1250 has a full range of protection (OVP / UVP / OPP / SCP / OCP / OTP), including protection against overload and overheating. The node is based on chip-supervisor Weltrend WT7527V.

Seasonic X-1250 (SS-1250XM2)

As always, the quality of the soldering has no complaints. All tracks are smooth, stains and other defects were not found. In this regard, the Sea Sonic Electronics products can be considered as a reference in the field of computer electronics.

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