Corsair HX520W & HX620W Modular power supplies

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The cooling of the Corsair PSUs worked well, especially considering the slow speed of the fan through the lower portion of the power tests. Temperature rise remained quite low and did not reach double digits until about the 250W mark. From 250W all the way to 620W, the temperature rise stayed at about 11~12°C. These are cool running PSUs.

One word of warning: Due to recent changes in our test bench, thermal results are not perfectly comparable to many of the earlier tests that we have done. Our new test bench uses a larger 120mm fan that provides a more realistic simulation of the kinds of low-noise systems that are in use today. Earlier tests used an 80mm exhaust fan which means the newer PSU cooling data may look a bit better; it may stay cooler to a higher load point.


Upon turn on, the PSU fan started at 3.84V. The system was audible at 1m, but very quiet and smooth. A slight buzzing could be heard with very low 12V or +5VSB loads, but it was mild and quickly dissipated once >3A was reached on the 12V line. At 65W load, there was just a trace of buzz and at 90W, there was none.

As the load increased, the fan voltage remain unchanged in our thermal test rig all the way to about 300W output load. This was true for both samples. The upgraded 120mm fan cooling in our test rig probably helped, but 22 [email protected] at 300W load is really about as good as you can expect any PSU to do. This is extremely quiet performance, the best we've encountered from any PSU.

Beyond 300W, the fan speed and noise climbed fairly quickly, as expected from Corsair's own graphs, but even at 400W output, the overall noise was still just this side of 30 dBA. That's pretty good, even though it is too loud to be considered very quiet.

One item worthy of note: Big changes in power load seemed to trigger a very quick response in the fan speed, almost as if the fan controller was sensing current instead of just temperature. A current-based fans controller seems unlikely though. The other explanation is that the thermistor is embedded inside a semiconductor, rather than being crudely glued onto a hot spot, which allows the fan controller to be much more responsive. The quick fan slowdown was pleasant when the load was reduced from maximum to modest. At the same time, the response was not so quick as to cause an up/down yo-yo effect in noise. Besides, the fan did not change speed till the power load was so high; by then other components in your system would probably be ramping up their fans and making plenty of noise.


Each of these recording have 10 seconds of silence to let you hear the ambient sound of the room, followed by 10 seconds of the product's noise.

Sound Recordings of PSU Comparatives


These recordings were made with a high resolution, studio quality, digital recording system, then converted to LAME 128kbps encoded MP3s. We've listened long and hard to ensure there is no audible degradation from the original WAV files to these MP3s. They represent a quick snapshot of what we heard during the review. Two recordings of each noise level were made, one from a distance of one meter, and another from one foot away.

The one meter recording is intended to give you an idea of how the subject of this review sound in actual use — one meter is a reasonable typical distance between a computer or computer component and your ear. The recording contains stretches of ambient noise that you can use to judge the relative loudness of the subject. For best results, set your volume control so that the ambient noise is just barely audible. Be aware that very quiet subjects may not be audible — if we couldn't hear it from one meter, chances are we couldn't record it either!

The one foot recording is designed to bring out the fine details of the noise. Use this recording with caution! Although more detailed, it may not represent how the subject sounds in actual use. It is best to listen to this recording after you have listened to the one meter recording.

More details about how we make these recordings can be found in our short article: Audio Recording Methods Revised.


The new Corsair PSUs are not only aimed at the power-demanding PC gamer, but also the growing class of quiet PC enthusiasts who also want to be able to run some seriously powerful gear. The HX620W and HX520W deliver clean, ultra-stable power under a wide range of demanding conditions. They also happen to be about the quietest fan-cooled PSUs we've tested to date, matching the best of the Seasonic S12s. They are also energy efficient, matching and even besting many of the 80 Plus certified models we've tested. The modular sleeved cables ease the challenges of keeping the system tidy and aerodynamic for optimal airflow, which is especially important if you wish to maximize cooling with the slowest of fans for the lowest noise. To top it all off, Corsair offers a five year warranty, which is the longest for any computer power supply we know of.

Given the manufacturing source, the most obvious comparatives are the Seasonic M12-500 and M12-600 models, which have the same basic circuitry and modular cable system, and probably the same noise-conscious fan control circuitry. However, the M12s have that extra 60mm fan. Although the 60mm fan is there for good reason — to clear a hot zone that seems endemic to all 120mm fan PSUs — once they turn on, admittedly at a high power load, they do not turn off. The small degree of noise the 60mm fan adds to the M12's signature at higher loads is enough for us to favor the S12 or S12 Energy Plus series in the Seasonic line... but they lack the modular detachable cables of the M12. Which leads us back to the Corsairs: They seem just about perfect for a quiet-loving power PC user who wants to have his cake but not hear it as well.

About the only thing SPCR could ask for are a couple more lower power models for those of us who seek to make a high efficiency, quiet, yet highly capable computer. 300W would be plenty for such a PC in these days of improving CPU efficiency. Perhaps if enough users pester Corsair (and Seasonic?)...

The final words: Great job, Corsair.

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SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended Units
Power Distribution within Six PCs
SPCR PSU Test Rig V.4
Seasonic S12 Energy Plus 550 and 660
Seasonic M12-700
Mushkin XP-650
Silverstone Element Plus ST50EF-Plus

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