SilverStone SX550 SFX PSU Review

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SilverStone continues to enrich its SFX PSU portfolio. One of the most recent additions is the SX550, a budget-oriented unit featuring Gold-class efficiency and fixed cables instead of modular ones. As you can tell, it's intended to bring prices down.

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Load Regulation, Hold-Up Time And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 
SilverStone SX550
SilverStone SX600-G
Silverstone SX500-GL

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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Despite the bulk caps' low combined capacity, the SX550's hold-up time easily surpass the ATX spec's requirement thanks to the ACRF topology. In addition, the power-good signal drops well before the rails go out of spec.

Inrush Current

For details on our inrush current testing, please click here.

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Inrush current is normal with 115 V input and a little higher than expected with 230 VAC.

Load Regulation And Efficiency Measurements

Our first set of tests reveals the voltage rails' stability and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the power supply's maximum in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5 V and 3.3 V) with a high load, while the load at +12V was only 0.1 A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails. 

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Test #12 V5 V3.3 V5 VSBDC/AC (Watts)EfficiencyFan SpeedFan NoiseTemps (In/Out)PF/AC Volts
12.765A1.964A1.964A0.995A54.7482.48%1495 RPM27.8 dB(A)39.75 °C0.971
12.002V5.081V3.359V5.007V66.3744.02 °C115.1V
26.589A2.960A2.959A1.200A109.7387.45%1495 RPM27.8 dB(A)39.83 °C0.982
11.970V5.063V3.343V4.988V125.4844.66 °C115.1V
310.764A3.466A3.479A1.405A164.8388.87%1690 RPM32.2 dB(A)40.94 °C0.991
11.961V5.051V3.331V4.970V185.4846.05 °C115.1V
414.947A3.974A3.978A1.615A219.7989.27%1860 RPM36.1 dB(A)41.53 °C0.996
11.949V5.034V3.316V4.949V246.2246.97 °C115.1V
518.798A4.979A5.000A1.823A274.7089.14%2140 RPM40.4 dB(A)42.22 °C0.998
11.929V5.017V3.298V4.931V308.1747.82 °C115.1V
622.666A6.000A6.029A2.035A329.7088.79%2560 RPM39.7 dB(A)43.27 °C0.998
11.909V5.000V3.282V4.908V371.3249.04 °C115.1V
726.554A7.020A7.065A2.249A384.6788.21%2810 RPM42.3 dB(A)43.90 °C0.999
11.886V4.981V3.268V4.887V436.0949.99 °C115.1V
830.476A8.061A8.118A2.462A439.5987.43%3140 RPM45.5 dB(A)44.15 °C0.999
11.852V4.963V3.252V4.867V502.8150.52 °C115.1V
934.901A8.585A8.669A2.468A494.6286.62%3345 RPM48.7 dB(A)44.75 °C0.999
11.806V4.951V3.241V4.854V571.0051.58 °C115.1V
1039.322A9.113A9.208A2.582A549.4185.61%3345 RPM48.7 dB(A)45.90 °C0.999
11.755V4.937V3.225V4.838V641.7653.85 °C115.1V
1144.405A9.131A9.232A2.586A604.1884.61%3345 RPM48.7 dB(A)46.50 °C0.999
11.643V4.929V3.216V4.826V714.0655.02 °C115.1V
CL10.097A14.021A14.002A0.000A116.1480.91%2605 RPM40.0 dB(A)43.88 °C0.985
11.984V4.949V3.256V5.004V143.5550.11 °C115.1V
CL244.965A1.003A1.003A1.000A542.7886.78%3345 RPM48.7 dB(A)46.12 °C0.999
11.776V5.013V3.296V4.938V625.4554.14 °C115.1V

Load regulation is mediocre on all rails and efficiency isn't particularly impressive under high operating temperatures. The SX550 manages to meet the 80 PLUS Gold requirements under 20 percent load. With 50 percent, it lands 0.86 percent away from the 90 percent target. The measurements get even worse under full load as efficiency drops below 86 percent. Obviously increased temperatures have a significant impact on the ACRF topology's performance.

With up to 20 percent load the fan's acoustic output is very low. Noise exceeds 40 dB(A), becoming noticeable especially to sensitive users, when the load level reaches 50 percent. With the fan spinning at close to 3350 RPM, the fan's noise doesn't exceed 50 dB(A). The fan profile definitely isn't aggressive, and the truth is that the small-diameter fan and moderate efficiency levels don't leave much room for a more relaxed ramp.

Aris Mpitziopoulos
Contributing Editor

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

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15 Comments Comment from the forums
  • turkey3_scratch
    It doesn't seem like Silverstone can get anything right these days. I don't see how they can't include a rubber grommet where the wires leave the cage. When people are bending those wires around the case, they can easily rub up against a sharp edge like that and cut through the insulation or even damage the wires and increase the resistance. For $95 this is a rip off, I think it should be priced at $75. It's pretty loud, too.

    Also, according to your thing the PS113 doesn't support OTP, even though this unit seems to. It also seems to support UVP. Doesn't quite make sense to me. http://www.tomshardware.com/reviews/power-supplies-101,4193-22.html
    Reply
  • Aris_Mp
    Most supervisor ICs don't support OTP, so this protection is implemented through other circuits in PSUs that actually have OTP.
    Reply
  • Clamyboy74
    Having few cables is the point of an sfx psu. Sfx cases don't have much driver space, and short wires are good for small cases. Who in their right mind would but an sfx psu for use in a mod tower case, especially with a $95 price tag? When you review sfx psu's please bear into consideration that these are made for use in small cases, where short cables, few connectors are deal breakers for consumers. Thank you.
    Reply
  • turkey3_scratch
    The thing that hurts this unit is that there is no common hardware configuration that will fit into an SFX case and require more than a 400W power supply like the Corsair SF which is much better. Most high-end AMD GPUs like the R9 390 are just way too large to even fit into an SFX case. If you think of cards that can actually fit into an SFX case, they are going to be small form factor cards, which are almost always under 200W, or these days even quite less. CPU overclocking to extremes can't be done in SFX cases with limited cooler sizes and due to airflow restrictions, so, really, I don't see a position in the market where this unit can be competitive over the Corsair SF400. And since this unit does not come with an SFX to ATX bracket, it is implied that nobody will probably install it into a case that takes an ATX PS2 power supply.
    Reply
  • AlistairAB
    I have the corsaif sf450 and can confirm it blows the silverstone out of the water (silverstone never fixed their fan problems with their sfx psus)
    Reply
  • Samer1970
    18459920 said:
    The thing that hurts this unit is that there is no common hardware configuration that will fit into an SFX case and require more than a 400W power supply like the Corsair SF which is much better. Most high-end AMD GPUs like the R9 390 are just way too large to even fit into an SFX case. If you think of cards that can actually fit into an SFX case, they are going to be small form factor cards, which are almost always under 200W, or these days even quite less. CPU overclocking to extremes can't be done in SFX cases with limited cooler sizes and due to airflow restrictions, so, really, I don't see a position in the market where this unit can be competitive over the Corsair SF400. And since this unit does not come with an SFX to ATX bracket, it is implied that nobody will probably install it into a case that takes an ATX PS2 power supply.

    how about Titan X Pascal cards / 1080 ti? They consume 435Watt total System power.
    Reply
  • turkey3_scratch
    Not quite samer and not cards that would fit in an SFX case.

    Also, my bad guys, I meant SF450 not 400.
    Reply
  • Samer1970
    18460559 said:
    Not quite samer and not cards that would fit in an SFX case.

    Also, my bad guys, I meant SF450 not 400.

    maybe you should check the following cases :

    http://www.fractal-design.com/home/product/cases/node-series/node-202

    http://www.silverstonetek.com/product.php?pid=533

    http://www.silverstonetek.com/raven/products/index.php?model=RVZ02

    https://www.ncases.com/

    https://www.dan-cases.com/
    Reply
  • turkey3_scratch
    If you own a 1080Ti why would you get a mediocre PSU like this anyway? Once again, it doesn't seem to have a purpose at all. Once power requirements get anywhere past 300W you probably have high-end hardware in which case a unit like this is a poor choice over the SF600.

    Budget power supplies over 500W really have no place in this world. People purchase budget power supplies over 500W for three reasons:

    1) They have high end hardware and underestimate the need for a quality PSU
    2) They are uninformed and think "more watts" is better.
    3) They overestimate their power requirements.

    I suppose you could argue if they have 225W of hardware a 550W unit like this is perfect in terms of efficiency. Okay, maybe so. But that depends on how much you value efficiency, I suppose.

    The unit still performs poorly compared to Corsair. It's true, Corsair SF dominate the SFX market with the best units.
    Reply
  • Samer1970
    18460649 said:
    If you own a 1080Ti why would you get a mediocre PSU like this anyway? Once again, it doesn't seem to have a purpose at all. Once power requirements get anywhere past 300W you probably have high-end hardware in which case a unit like this is a poor choice over the SF600.

    Budget power supplies over 500W really have no place in this world. People purchase budget power supplies over 500W for three reasons:

    1) They have high end hardware and underestimate the need for a quality PSU
    2) They are uninformed and think "more watts" is better.
    3) They overestimate their power requirements.

    I suppose you could argue if they have 225W of hardware a 550W unit like this is perfect in terms of efficiency. Okay, maybe so. But that depends on how much you value efficiency, I suppose.

    The unit still performs poorly compared to Corsair. It's true, Corsair SF dominate the SFX market with the best units.

    Does not need to be 1080 ti , any 250 watt GPU card ... from 390 , 390x to others .. there are people on budget and use such cards in compact systems .

    I just mentioned gtx 1080 ti as a modern example ..
    Reply