FSP DAGGER PRO 550W SFX Power Supply Review

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The FSP DAGGER PRO 550W is the third SFX power supply we have seen here at TheFPSReview from FSP. However, FSP has been around for a very long time now producing not only SFX units but ATX12/EPS form factor units and other form factors as well. The branching out to pushing their own brand, rather than simply being an OEM, has been a more modern development and has represented a real growth area for them. So, it is once more interesting to be able to take a look at not only an FSP branded unit but one that dabbles in something a bit different; the SFX form factor. Will this SFX unit put a DAGGER through the heart of the competition? Or is this blade just too dull? Let’s see.

Build Quality

Today’s FSP DAGGER PRO 550W starts things off with a build quality that is very good but also a bit curious at times. Sure, the exterior design looks like the recent FSP SFX PRO 450W and that is to be expected given size, manufacturer branding, etc. However, when we move to the interior we see that the platform is different from that unit but still a more value-oriented ACRF design than we have seen from other SFX units (except FSP). So that is a bit curious. Looking further at the interior, the integration and soldering quality looks to be very good. The component selection is again somewhat curious as it features Nippon Chemi-con and Rubycon standard electrolytics paired with Teapo solid capacitors. This is all coupled with a manual that is not so great and a 5-year warranty.

Load Testing

Today’s FSP DAGGER PRO 550W provides us with both excellent results and not so excellent results. We saw voltage regulation of up to 0.06v on the 12v rail, 0.02v on the 5v rail, and 0.01v on the 3.3v rail. Those are excellent results and they make this unit easily better than the full ATX12v/EPS sized Bitfenix Formula Gold 550W we saw some time ago. Now, in addition to that, we saw efficiency that ranged from 85.57% to 88.14% efficient at 120v AC input and 85.08% to 87.31% efficient at 100v AC input. By themselves, these efficiency numbers would be good, but these are well below what we saw from the Formula Gold 550W and they also fall short of the 80 Plus Gold standards. True, we do not use the same equipment or environmental parameters as 80 Plus in our regular load tests, but units that actually meet that advertisement usually track closer to it in our tests than this. Sadly, at the time of testing, this unit was not listed by ECOS/ECOVA for us to know for sure though.

When we look at the Transient Load Tests results for the FSP DAGGER PRO 550W today, we again results are excellent and then not so excellent. When directly loaded, the 12v rail showed a peak change of ~400mV, and the 5v rail had a peak change of ~45mV. During the 12v load, the unloaded 5v rail saw a peak change of ~35mV. In absolute terms, these results are passing with the 5v results even being excellent. However, the 12v results were not and that is why this unit was, again, mixed with the Bitfenix Formula Gold 550W.

DC Output Quality

The DC Output Quality results for the FSP DAGGER PRO 550W were passing which is good but they were not great for one big reason. That big reason is, we saw peak values of ~60mV on the 12v rail. That is 1/2 of the ATX12v/EPS specification limit and much worse than what the Bitfenix Formula Gold 550W gave us. This was followed by ~20mV on the 5v rail and ~10mV on the 3.3v rail. These values are within specification limits but, they are not doing that much better than the Formula Gold 550W. So, overall, this unit is once more passing but it has just one thing that is not impressing us in this test.


Today’s FSP DAGGER PRO 550W is a small(ish) capacity unit with a double ball-bearing fan in an SFX form factor and efficiency levels that don’t quite lineup with where we expect them to be. Unfortunately, SFX units, like this, often get used in quiet cooling environments. So, how does this all stack up?

Let me refer back to my notes. Test #1, nothing. Test #2, “wow, it is burning up. That smell, the smell of death surrounds you, uh.” Test #3, “I think I am going to develop permanent tinnitus from this unit”. Test #4, “Hey, I can’t hear the power supply anymore! Wait, I can’t hear ANYTHING anymore!”

Final Points

The FSP DAGGER PRO 550W is a passing power supply today. The DAGGER PRO 550W gave us very good build quality, excellent voltage regulation, passing DC Output Quality and passing Transient Load results but it was not exactly quiet. As you see, this is a bit of a mixed bag. However, that is somewhat expected for SFX-sized products as you can’t get everything in such a small package. That said, what is the price (because that can fix an awful lot)?

Today, we find that the DAGGER PRO 550W can be had for around $119.99 at Amazon with Free Prime Shipping. That certainly sounds like a lot, because it is a lot. However, almost every comparable SFX unit is priced similarly. So, it very much comes down to performance and, today, that seems to be a bit of a stretch. The DAGGER PRO 550W certainly has its moments where it slices and dices its way through the competition. However, a Dagger is a two-sided weapon and it just feels like when we flip the blade over to use the other edge that someone forgot to sharpen both sides. If you are ok with the noise output from this unit and some of the other shortfalls then it will serve you well enough. However, if those issues matter to you then you probably won’t be happy with this unit unless someone takes a Dagger to the price.  


Paul Johnson
Paul is a long time PC hobbyist and tech enthusiast having gotten his start when he broke his first C64 quickly followed by breaking his first IBM XT. Most notably however, for 12 years, he served as the Power Supply Editor for one of the truly early, groundbreaking, and INDPENDENT PC enthusiast sites ([H]ardOCP) until its mothballing in April of 2019. Paul now brings the same flair and style of his power supply reviews to The FPS Review.

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