Corsair RM750 Power Supply Review: Affordable Yet Powerful
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Transient Response Tests, Ripple Measurements and EMC Pre-Compliance Testing
Advanced Transient Response Tests
For details about 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.
We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology we also choose to apply a worst case scenario with no extra capacitance on the rails.
Advanced Transient Response at 20% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.102V | 11.942V | 1.32% | Pass |
| 5V | 5.035V | 4.952V | 1.65% | Pass |
| 3.3V | 3.296V | 3.153V | 4.34% | Pass |
| 5VSB | 5.014V | 4.963V | 1.02% | Pass |
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.098V | 11.890V | 1.72% | Pass |
| 5V | 5.035V | 4.933V | 2.03% | Pass |
| 3.3V | 3.297V | 3.119V | 5.40% | Fail |
| 5VSB | 5.013V | 4.932V | 1.62% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.099V | 11.915V | 1.52% | Pass |
| 5V | 5.035V | 4.940V | 1.89% | Pass |
| 3.3V | 3.296V | 3.113V | 5.55% | Fail |
| 5VSB | 5.013V | 4.940V | 1.46% | Pass |
Advanced Transient Response at 50% – 200ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.045V | 11.958V | 0.72% | Pass |
| 5V | 5.026V | 4.939V | 1.73% | Pass |
| 3.3V | 3.290V | 3.138V | 4.62% | Fail |
| 5VSB | 4.995V | 4.933V | 1.24% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.040V | 11.934V | 0.88% | Pass |
| 5V | 5.026V | 4.916V | 2.19% | Pass |
| 3.3V | 3.292V | 3.108V | 5.59% | Fail |
| 5VSB | 4.994V | 4.914V | 1.60% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
|---|---|---|---|---|
| 12V | 12.042V | 11.934V | 0.90% | Pass |
| 5V | 5.026V | 4.929V | 1.93% | Pass |
| 3.3V | 3.292V | 3.110V | 5.53% | Fail |
| 5VSB | 4.995V | 4.925V | 1.40% | Pass |
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The +12V rail's voltage drops are controlled and the same applies for the 5V rail. On the contrary, the 3.3V rail registers the worst performance here, failing in almost all tests.
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.
Everything is perfect here.
Ripple Measurements
Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' lifespan because it causes them to run hotter. A 10 degrees Celsius increase can cut into a cap's useful life by 50%. Ripple also plays an important role in overall system stability, especially when overclocking is involved.
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The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).
| Test | 12V | 5V | 3.3V | 5VSB | Pass/Fail |
|---|---|---|---|---|---|
| 10% Load | 4.7 mV | 6.2 mV | 8.6 mV | 7.8 mV | Pass |
| 20% Load | 5.5 mV | 6.6 mV | 10.1 mV | 8.3 mV | Pass |
| 30% Load | 10.7 mV | 7.4 mV | 10.0 mV | 9.2 mV | Pass |
| 40% Load | 9.1 mV | 8.1 mV | 10.3 mV | 8.0 mV | Pass |
| 50% Load | 9.1 mV | 9.3 mV | 12.5 mV | 9.3 mV | Pass |
| 60% Load | 9.0 mV | 9.2 mV | 11.9 mV | 8.7 mV | Pass |
| 70% Load | 10.3 mV | 9.8 mV | 12.1 mV | 8.7 mV | Pass |
| 80% Load | 10.3 mV | 10.5 mV | 12.8 mV | 8.9 mV | Pass |
| 90% Load | 11.7 mV | 11.0 mV | 14.6 mV | 11.1 mV | Pass |
| 100% Load | 16.6 mV | 12.0 mV | 14.9 mV | 9.5 mV | Pass |
| 110% Load | 17.7 mV | 13.4 mV | 15.9 mV | 9.3 mV | Pass |
| Crossload 1 | 20.8 mV | 10.7 mV | 15.8 mV | 9.0 mV | Pass |
| Crossload 2 | 15.8 mV | 10.4 mV | 12.9 mV | 9.0 mV | Pass |
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Even without cables featuring in-line caps, the RM750 achieves top ripple performance.
Ripple At Full Load
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Ripple At 110% 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.
Some high spurs, but none of them goes above the respective limits, so everything is fine here.
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Aris Mpitziopoulos is a contributing editor at Tom's Hardware, covering PSUs.
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DSzymborski It's really hard to recommend this at the price. Offer this at $75 and it's interesting, but there's always something better at this price that'll undercut it and a few additional sales that put under this (SeaSonic Focus, EVGA G3, etc). I don't think this is even competitive at $100.Reply