Voltage Regulation

+3.3V Regulation/Ripple and Noise
Load Voltage
5% +1.52% (2mV)
10% +1.52% (3mV)
20% +1.52% (12mV)
50% +0.91% (11mV)
80% +0.61% (21mV)
100% +0.30% (23mV)
110% +0.30% (25mV)
Crossload +12V max. +1.52%
Crossload +3.3V/+5V max. +1.21%


+5V Regulation/Ripple and Noise
Load Voltage
5% +3.40% (2mV)
10% +3.40% (5mV)
20% +3.20% (12mV)
50% +3.00% (17mV)
80% +2.40% (17mV)
100% +2.40% (20mV)
110% +2.40% (22mV)
Crossload +12V max. +0.20%.
Crossload +3.3V/+5V max. -0.20%


+12V Regulation (Worst Ouput)/Ripple and Noise (Worst Output)
Load Voltage
5% +1.42% (7mV)
10% +0.92% (15mV)
20% +0.75% (25mV)
50% +0.58% (38mV)
80% +0.58% (40mV)
100% +0.92% (47mV)
110% +0.75% (51mV)
Crossload +12V max. +0.42%
Crossload +3.3V/+5V max. +1.33%

Noise Levels

Loudness and Temperatures (Δϑ to 22.1 °C ambient temperature)
Load Opinion
5% choke chirping (1.7 °C)
10% choke chirping (2.6 °C)
20% choke chirping (4.6 °C)
50% choke chirping (8.3 °C)
80% choke chirping (15.9 °C)
100% choke chirping (18.6 °C)
110% choke chirping (20.8 °C)

Efficiency and PFC

Efficiency and Power Factor 115 VAC
Load Efficiency PFC
5% 71.19% 0.879
10% 85.40% 0.911
20% 89.53% 0.958
50% 91.82% 0.988
80% 91.09% 0.991
100% 90.74% 0.992
110% 89.47% 0.993


Efficiency and Power Factor 230 VAC
Load Efficiency PFC
5% 73.67% 0.864
10% 85.86% 0.883
20% 90.10% 0.939
50% 92.14% 0.984
80% 91.60% 0.988
100% 91.06% 0.990
110% 90.84% 0.990

Since there is no fan, there's not much point in measuring sound pressure levels, but what about noise from the electronics? There is an audible "chirping" from the PFC choke and both DC-to-DC converters. However, this could be an individual case. The difference between the ambient and the exhaust temperature is relatively high. We've tested the power supply with a room temperature of just 22.1 °C, which is usually no problem for a high-quality PSU.

The voltage quality is absolutely acceptable. Small transients are no big deal and the smaller rails are always below 25mV which is less than 0.5% ripple. +12V shows only 51mV,  but we should keep in mind that Seasonic had no more than 20mV on all outputs. Overall the voltage regulation is decent. There is hardly any drop on the +12 V and +3.3V rail but +5 V could be closer the optimal value.

Considering the 80 Plus Gold certification, we expected high efficiency and that's exactly what we got. The only blemish is that 5% load "only" comes in at 71-74%. At this point the efficiency could be better than 75%, but we don't want to overdo things.

Internal Design and Components Conclusion
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  • mtoma - Sunday, April 22, 2012 - link

    Well, all I can say that the value proposition it's relative. For silent PC enthusiasts, it is well, well worth the extra cost. For the others, I say only that the Seasonic units don't accumulate heat (the temperatures are about the same as a HDD with 5400 rpm) and dust.
  • Iketh - Friday, April 20, 2012 - link

    The efficiency results fit the platinum specification, no? What am I missing here?
  • Martin Kaffei - Friday, April 20, 2012 - link

    It's quite close, but you need 90% @ 20% load and 115V and 92 % @ 50% load and 115V. The results for 230V are always higher, but 80Plus works with 115V input.
  • popej - Friday, April 20, 2012 - link

    Basically fanless PSU doesn't make fanless PC. So why bother and pay more?
  • mariush - Friday, April 20, 2012 - link

    It can be nearly inaudible.

    I've mounted an Accelero S1 rev 2 on my Radeon 4850, so it's completely silent.
    The power supply is a Seasonic X-650 which turns off the fan at below about 170 watts of usage.

    So all there's left is the CPU fan which is a low noise 120mm Zerocool fan and a low speed fan cooling down my 4 hard drives.

    This computer is obviously not suitable to be completely silent, due to the heat generated by the hard drives and the old processor (Intel Q6600).

    But, there are AMD and Intel processors that run with just a large heatsink (and even more models would run passively with a bit of downclocking) and if you use a SSD, you then have a completely passively cooled system.

    It's really not that hard to achieve that.... and once you do this, you'll be wondering how you lived for so much time with fans buzzing you constantly.
    I personally spotted the difference (or should i say improvement) caused by lowering the number of working fans in my computer.
  • kmmatney - Friday, April 20, 2012 - link

    I also have an Accelero S1 Rev2 on an HD4890. It can run passively cooled, but I still lashed up a 90 mm fan (with a resistor to reduce speed) just to get a little airflow and peace of mind. I bought several fan resistors years ago, and they allow you to get silence while using cheap fans.

  • ZekkPacus - Friday, April 20, 2012 - link

    It's more than possible to do, though, and in that kind of system this kind of PSU is ideal. Graphics cards are available up to the HD6850 that are passively cooled, plenty of options between the 6570-6770 or the GT440 for nVidia. Any Sandy Bridge CPU 65W or less can be easily passively cooled, either with a Nofen heatsink or a large (Thermalright or Scythe) tower heatsink. Hell there's an i5-2500T (only available OEM, you're not SUPPOSED to be able to buy it retail but you could probably find somewhere that would sell it), quad core CPU with a 45W TDP. SSDs are silent in operation. A good case with enough venting (especially top venting), and the noisiest thing in it would be an optical drive.

    It's very tempting sometimes.
  • Sivar - Friday, April 20, 2012 - link

    I wrote an (ad-free) article about a completely fanless system I built. The case was far less than ideal, but I've since used better cases. It's important to have a fan grill at the top to allow heat to passively rise but it is not required.
    I usually build fanless systems for reliability and low-maintenance (no dust), but I'd not attempt to build a fanless gaming PC. A Geforce 580 would require a heat exchanger the size of another computer case.

  • jwilliams4200 - Friday, April 20, 2012 - link

    NoFan, a Korean company, makes components and complete systems that are entirely fanless. For some reason their products are not sold in the US, but quietpc in the UK carries them:


    The CR95-C "Icepipe" cooler is interesting. It is bigger than the Thermalright HR-02 although less surface area, and seems to be quite a bit more open -- probably a good thing for natural convection cooling. Unfortunately it blocks the first PCIe slot of your motherboard, and it can interfere with the top of your case (I had to cut a bit of metal off the top of my Xigmatek Midgard II case in order to get it to fit)
  • Sivar - Friday, April 20, 2012 - link

    Good link; I've never seen that unit, and I did a lot of searching once the HR-02 became difficult to find. Thanks!

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