Seasonic PRIME Ultra Platinum 550W PSU Review: Power Supply Perfection

  • Excellent build quality
  • Clean, efficient power
  • Near silent operation
  • Industry best 12-year warranty

Seasonic sent us their Prime Ultra Platinum 550W power supply for review and we included it in our In Win 101C build. Since the 1980’s Seasonic has been building quality power supplies and is one of the most respected power supply manufacturers. We can attest to this as Seasonic has long been a trusted and heavily relied upon power supply brand here at Performance Computer. In fact we’ve never had a Seasonic unit fail on us and that’s after heavy use and plenty of overclocking! If you’re considering building a new PC or are bringing an older one up to date, here’s why you should be looking at Seasonic’s Prime Ultra Platinum series.

seasonic prime ultra platinum review

Unboxing & Included Parts

The Prime Ultra Platinum series has five models, the 550W, 650W, 750W, 850W and 1000W. They are all fully modular and backed by Seasonic’s confident 12-year warranty.

The box has Seasonic’s logo as well as the Prime Ultra Platinum branding, the wattage amount, 80 Plus Platinum badge and a proudly displayed 12-year warranty badge.

seasonic prime ultra platinum 550w power supply review

The back of the box has some information about the power supply, its fan, hybrid fan control mode, high quality premium Japanese capacitors, etc. as well as a photo of the unit.

seasonic prime ultra platinum psu review

When is immediately apparent upon opening the box is quality which is present in all aspects of this unit, the power supply comes in a nice velvet bag and is safely secured with two form fitting foam panels. The modular cables come in a bag of their own. These are nice touches that simply aren’t included with cheap power supplies.

Speaking of cables, aside from a standard power cable, here’s what’s included with the 550W model:

  • 1x 24-pin power cable
  • 1x 8-pin CPU power cable
  • 1x 6+2 pin PCIe power cable with two connectors
  • 1x SATA power cable with four connectors
  • 1x SATA power cable with two connectors
  • 1x Molex/Peripheral cable with three connectors
  • 1x Floppy power cable with one connector

Additional accessories include:

  • A 24-pin power supply tester
  • 4x case mounting screws
  • Several zip ties for cable management
  • Premium velcro wraps for additional cable management
  • A case badge

seasonic prime ultra platinum cables

The 24-pin PSU tester is especially nice if you are filling a custom water cooling loop as it allows you to bypass the motherboard and simply turn on power to the pump to cycle liquid through your loop.

The power supply itself is one of the best-looking units we’ve ever seen. The satin black case has a premium feel and a great weight.

seasonic prime ultra platinum hybrid fan

The top displays the model and serial numbers, AC input and DC output information as well as the 80 Plus Platinum certification badge.

seasonic prime ultra platinum 550w review

The front has the cable connectors, nicely organized and labeled.

seasonic prime ultra platinum connectors

The back has the AC cable connector, power switch and hybrid mode switch.

seasonic prime ultra platinum hybrid switch

Components & Technology

The Prime Ultra Platinum series is a fully modular set of power supplies. This means you can choose which cable are plugged-in to the PSU based on how many components you have in your system. This results in cleaner builds, eliminating unused cabling. More on this will be available in an upcoming power supply comparison article. The included cables are matte black and have a flat design aside from the 24-pin cable which has a neatly braided design.

in win 101c cable management after

This new power supply design includes some improved technology Seasonic dubs “Micro Tolerance Load Regulation”. Essentially what this means is that the output voltage is kept within a very tight range, maintaining smoothly steady power in demanding high-performance systems.

seasonic prime ultra platinum power supply

Seasonic also employs a hybrid fan technology in the Prime Ultra Platinum series, meaning that when activated via the switch in the back, noise is kept to the minimal level allowable under the current load. The fan is does not operate until the current load reaches at least 40%. This resulted in a very quiet experience in our build, in fact we couldn’t hear any noise at all from the PSU and any noise it did generate was drowned out by our radiator and case fans.

seasonic prime ultra platinum side

Speaking of the fan, the Prime Ultra Platinum’s fan utilizes a fluid dynamic bearing. Without getting too technical, fluid dynamic fan bearings use oil to improve the lubrication of the bearing thus resulting in a longer service life, all while retaining the low noise benefits of a sleeve-bearing fan.

Finally, Seasonic added a cable-free design to the PCB and back panel, connecting them with a copper plate further improving output power quality.


Power supplies are often overlooked and under-researched by novice PC builders and I can’t stress enough the importance of choosing a PSU that delivers clean, efficient power. The Seasonic Prime Ultra Platinum series accomplished this in spades. Combine flawless performance with a fully modular design, nearly silent operation and a 12-year warranty and you have a product that is well worth spending a little more on. Don’t compromise on arguably the most vital component in your computer. We highly recommend Seasonic’s Prime Ultra Platinum series to new and veteran PC builders alike!

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