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Corsair AX850 PSU Review: Top Performer and Dead Silent

Editor's Choice

Transient Response Tests, Ripple Measurements and EMC Pre-Compliance Testing

Advanced Transient Response Tests

For details on our transient response testing, please click here.

In the real world, power supplies are always working with loads that change. It's of immense importance, then, for the PSU to keep its rails within the ATX specification's defined ranges. The smaller the deviations, the more stable your PC will be with less stress applied to its components. 

Advanced Transient Response at 20 Percent – 200ms


Advanced Transient Response at 20 Percent – 20ms


Advanced Transient Response at 20 Percent – 1ms


Advanced Transient Response at 50 Percent – 200ms


Advanced Transient Response at 50 Percent – 20ms


Advanced Transient Response at 50 Percent – 1ms

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The transient response is fantastic on all rails! The AX850 is not only highly efficient, but also capable of handling tough transient response scenarios without sweating.

Turn-On Transient Tests

In the next set of tests, we measure the PSU's response in simpler transient load scenarios—during its power-on phase. Ideally, we don't want to see any voltage overshoots or spikes since those put a lot of stress on the DC-DC converters of installed components.

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The results are good, since we don't notice any large spikes or voltage overshoots.

Ripple Measurements

Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' life span because it causes them to run hotter. A 10°C increase can cut into a cap's useful life by 50 percent. Ripple also plays an important role in overall system stability, especially when overclocking is involved.

The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).

10% Load6.7 mV4.3 mV8.6 mV6.8 mVPass
20% Load8.3 mV4.6 mV9.0 mV7.1 mVPass
30% Load9.2 mV5.2 mV9.6 mV7.2 mVPass
40% Load5.7 mV5.8 mV9.9 mV8.0 mVPass
50% Load5.6 mV4.7 mV9.7 mV8.0 mVPass
60% Load6.0 mV5.1 mV9.7 mV8.5 mVPass
70% Load6.7 mV5.0 mV10.3 mV8.3 mVPass
80% Load6.9 mV5.1 mV10.6 mV8.9 mVPass
90% Load6.8 mV5.1 mV10.4 mV8.1 mVPass
100% Load10.8 mV5.8 mV11.8 mV9.6 mVPass
110% Load10.9 mV5.7 mV12.5 mV10.1 mVPass
Crossload 18.9 mV5.1 mV12.0 mV7.8 mVPass
Crossload 210.9 mV5.5 mV10.7 mV9.6 mVPass
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The ripple suppression is great on all rails, especially at 5V where it doesn't exceed 10mV even in the worst case scenario. Obviously the addition of in-cable caps plays a role here.

Ripple At Full Load

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Ripple At 110-Percent Load

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Ripple At Cross-Load 1

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Ripple At Cross-Load 2

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EMC Pre-Compliance Testing – Average & Peak EMI Detector Results

Electromagnetic Compatibility (EMC) is the ability of a device to operate properly in its environment without disrupting the proper operation of other close-by devices.

Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other close-by devices if too high. For example it can be the cause of increased static noise in your headphones or/and speakers.

Average EMI Detector

Peak EMI Detector

The conducted EMI emissions are below the corresponding limits with both average and peak detectors.

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Aris Mpitziopoulos
Aris Mpitziopoulos

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