Cold Test Results

For PSU testing, 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.

Right off the bat, the SeaSonic Focus Plus Gold 750FX behaves a little strangely in terms of electrical conversion efficiency. While most designs easily meet the 80Plus efficiency certification requirements at an input voltage of 115V AC – where the standard’s requirements are more lenient – the Focus Plus Gold 750FX greatly surpasses the 80Plus Gold certification requirements with an input voltage of 230V AC, only for the unit to struggle when powered from a 115V AC source. When the input voltage is 230V AC, the average efficiency across the nominal loading range is over 91.5%, an amazing figure for a mainstream PSU. If the input voltage is 115V AC, the efficiency plummets by nearly 3 percentage points across the entire load range, with the PSU barely meeting the 80Plus Gold certification requirements.

The default thermal control mode for the SeaSonic Focus Plus Gold 750FX adopts a semi-fanless cooling strategy, meaning that the fan will start only when it needs to. In our case, the fan started once the load surpassed 215-220 Watts. Naturally, the lack of active cooling under low loads means that the internal temperatures of the PSU will be comparatively higher than those of a full-time actively cooled PSU, but the temperature of the PSU quickly stabilizes one the fan starts. The internal temperatures of the SeaSonic Focus Plus Gold 750FX are mediocre for such an efficient product.

A look at the sound pressure level chart reveals that the active cooling requirements of the SeaSonic Focus Plus Gold 750FX are quite low. The fan does not even start before the load is greater than 200 Watts. When the fan eventually starts, the sound pressure is at practically inaudible levels while the load is below 400 Watts, after which point the thermal controller will keep increasing the speed of the fan in order to cope with the rising cooling requirements of the PSU.

The SeaSonic Focus Plus Gold 750FX PSU Hot Test Results (~45°C Ambient Temperature)


View All Comments

  • Dragonstongue - Thursday, May 16, 2019 - link

    I myself have the Seasonic G650 (SSR-650RM)
    is whisper quiet and rock stable. I have not really loaded to the hilts, however main review places including JohnnyGuru listed as very solid including above its rating (without getting uber overheat in the process)

    The other reason I like this vs many of the new Focus ones (plus, gold etc) it has 2 CPU power connectors (1 4+4 on main leads with 20+4 mainboard etc) and if need, can add additional 4+4 for the more power hungry or w/e kit that requires a 2nd eps connector.

    many of the new ones do not get this 2nd connector till the 900w range (pretty sure the 850s not have, at least when I went through them they did not, more of everything, but that connector, granted most boards work off 4+4 just fine including overclock, but there are some boards that "require" for various reasons that 2nd connector.

    EVGA makes some "modeled" after these from their GQ and so forth lines (just as good in most cases, have to back check the model number takes but a few moments .. I believe for EVGA would be G2 P2 and up type deal, I forget ut one of their lines was def more "budget" I think was the "Q" in model number (I could be very wrong)

    Anywho, thank you for the review, they really do solid PSU Seasonic does, that is why they are #1 for consumer grade PSU applications.
  • DanNeely - Thursday, May 16, 2019 - link

    Newegg lists 7 dual EPS models in the 600-650W class. Nothing smaller though; hopefully they'll continue to trickle down 500W would be enough for a lot of non-GPU centric HEDT systems.

    It's a real shame that the way the EPS and PCIe 12v standards evolved that we've got 2 mutually incompatible 8 pin 12V connectors. It'd've made things so much simpler going forward.
  • Death666Angel - Thursday, May 16, 2019 - link

    Since it's really just GND and +12V, all you need is an adapter cable. Or if you want it tidy, just buy an EPS plug and switch the pins from a PCIe plug (and loop a GND and +12V). Anything modular you can also just see how the layout is and get another EPS cable, often they are identical at the PSU side to the PCIe cables. Reply
  • schujj07 - Thursday, May 16, 2019 - link

    I have built several PCs with the Seasonic Focus Gold, semi-modular version of the Focus line and without the semi silent piece, and they are awesome. The Focus/Focus Plus line is my go to recommendation for people who are looking to build a PC or upgrade their PSU. Reply
  • GeoffreyA - Thursday, May 16, 2019 - link

    Greetings, sir, and thank you for this review. If I may, I'd like to ask a question concerning the semi-modular, non-plus, Focus Gold units (specifically the 450W and 550W models: the SSR-450FM and SSR-550FM). I wonder, will they be more or less the same quality as the Plus versions, and are they recommended? Online, reputable reviews of these units are sorely lacking.

    Much thanks and have a good day.
  • vidal6x6 - Thursday, May 16, 2019 - link

    I have Here a old 800w 11 years and It is rock and solid performance. now without cooler :)
    Dead silence! Running 2 xeon L5630 and a 660TI
  • KAlmquist - Saturday, May 18, 2019 - link

    In general it's hard to judge the quality of lower power units based on reviews of units with higher power rating. I believe that lower power units are (1) likely to face more intense price competition and (2) are less likely to be looked at by reviewers. So there is an incentive for manufacturers to cut corners on the lower power units.

    I also note that the unit reviewed here is from the FX line, whereas the units you are asking about are from the FM line. The FX line has a 10 year warranty. The FM units come with a shorter, although still respectable, 7 year warranty.

    That said, Seasonic has built up a reputation over a long period of time, and I'd confident buying Seasonic based on brand alone. If we were talking about any other manufacturer, I'd say you shouldn't buy a power supply without seeing a review, but I make an exception for Seasonic power supplies.
  • GeoffreyA - Saturday, May 18, 2019 - link

    Thank you for your response, KAlmquist. I do appreciate it, and completely agree with you. Seasonic certainly has a reputation for quality.

    I am going down a fairly budget path and will be buying the 450W FM unit this July (or one of these months). I'm just waiting for AMD to release Ryzen 3000. The Ryzen 3 3200G, if there turns out to be such a CPU, is likely what I will get (even though it won't actually be Zen 2).

    Thanks again and take care.
  • Death666Angel - Saturday, May 18, 2019 - link

    As long as you stay in the respective line up (e.g. 750W Gold FX Edition reviewed vs 450W Gold FX Edition bought) it is usually pretty similar to identical. If you buy a PSU from a manufacturer because another series higher power (higher cost) PSU did well in a review, you might get a bit of a surprise. However, if you stay with certain brands / OEMs, you are fine. I inherently trust anything Seasonic, Silverstone, Corsair with 80+ bronze. Something like Cougar, Cooler Master, NZXT, Super Flower, XFX, Sharkoon , Thermaltake can be fine or great even. They also sometimes have good sales. But they can also have duds. Although not as much as back in the day. There used to be a saying in German "don't buy a 'Chinaböller' [chinese fireworks]" when talking about these low tier brands. It's not that bad anymore. But I'd still get a used decent brand PSU than a new questionable one without reviews. I think Cougar once had a "scandal" where their 80+ certificate was achieved by another design that was not actually sold. Those things happen increasingly rarely (what doesn't sound right) and are eventually exposed and you might get some of your money back because of false advertising. But mostly 80+ certification is pretty good, consistent and reliable. Reply
  • GeoffreyA - Sunday, May 19, 2019 - link

    Thank you for the advice, Death. And you're quite right. I learned years ago what a no-name PSU can do to a computer. Back then, my old Athlon 64 survived but was never quite the same again. I replaced it with a somewhat better one: an AOpen unit seemingly made by FSP, but the damage had already been done.

    I will get the SSR-450FM unit (or the 550 one if I can afford it). Indeed, they are from the value line but do carry a 7-year warranty (and are 80+ gold). The funny part is, in my country, South Africa, Seasonic units are impossible to find, yet lesser units are doing the rounds. At any rate, I'll buy the Seasonic from Amazon.

Log in

Don't have an account? Sign up now