Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.
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 additional capacitance on the rails.
Advanced Transient Response at 20% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
| 12V | 12.059V | 11.871V | 1.56% | Pass |
| 5V | 5.024V | 4.928V | 1.91% | Pass |
| 3.3V | 3.346V | 3.187V | 4.76% | Pass |
| 5VSB | 5.071V | 5.005V | 1.30% | Pass |
Advanced Transient Response at 20% – 10ms
| Voltage | Before | After | Change | Pass/Fail |
| 12V | 12.055V | 11.878V | 1.47% | Pass |
| 5V | 5.024V | 4.926V | 1.96% | Pass |
| 3.3V | 3.346V | 3.187V | 4.75% | Pass |
| 5VSB | 5.071V | 5.013V | 1.15% | Pass |
Advanced Transient Response at 20% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
| 12V | 12.052V | 11.856V | 1.62% | Pass |
| 5V | 5.024V | 4.933V | 1.82% | Pass |
| 3.3V | 3.346V | 3.185V | 4.82% | Pass |
| 5VSB | 5.072V | 5.023V | 0.97% | Pass |
Advanced Transient Response at 50% – 20ms
| Voltage | Before | After | Change | Pass/Fail |
| 12V | 12.029V | 11.846V | 1.52% | Pass |
| 5V | 5.018V | 4.920V | 1.95% | Pass |
| 3.3V | 3.340V | 3.174V | 4.97% | Pass |
| 5VSB | 5.049V | 4.986V | 1.25% | Pass |
Advanced Transient Response at 50% – 10ms
| Voltage | Before | After | Change | Pass/Fail |
| 12V | 12.026V | 11.863V | 1.35% | Pass |
| 5V | 5.018V | 4.918V | 2.00% | Pass |
| 3.3V | 3.340V | 3.176V | 4.92% | Pass |
| 5VSB | 5.049V | 4.999V | 0.99% | Pass |
Advanced Transient Response at 50% – 1ms
| Voltage | Before | After | Change | Pass/Fail |
| 12V | 12.024V | 11.824V | 1.66% | Pass |
| 5V | 5.018V | 4.919V | 1.97% | Pass |
| 3.3V | 3.340V | 3.173V | 5.01% | Pass |
| 5VSB | 5.049V | 4.993V | 1.10% | Pass |
Transient response is not among the best we have seen so far. You cannot call it bad, though.
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.
There is a small step at 5VSB, which shouldn't be there, and another one in the "PSU OFF to Full 12V" test which can cause trouble in some mainboards. The rails must increase linearly and in a straight line between point A and B in these tests.
Power Supply Timing Tests
There are several signals generated by the power supply, which need to be within specified, by the ATX spec, ranges. If they are not, there can be compatibility issues with other system parts, especially mainboards. From year 2020, the PSU's Power-on time (T1) has to be lower than 150ms and the PWR_OK delay (T3) from 100 to 150ms, to be compatible with the Alternative Sleep Mode.
| T1 (Power-on time) & T3 (PWR_OK delay) | ||
|---|---|---|
| Load | T1 | T3 |
| 20% | 80ms | 286ms |
| 100% | 82ms | 282ms |
The Power-on time is notably below 100ms, but the PWR_OK delay is way over the 100-150ms region, so the PSU does not support the alternative sleep mode recommended by the ATX spec. This is strange given that the A750GF is ASM compatible.
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-degree 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.
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 | 13.2 mV | 14.7 mV | 18.3 mV | 6.2 mV | Pass |
| 20% Load | 16.7 mV | 14.5 mV | 19.0 mV | 10.2 mV | Pass |
| 30% Load | 18.1 mV | 14.8 mV | 19.4 mV | 7.7 mV | Pass |
| 40% Load | 18.3 mV | 14.9 mV | 17.9 mV | 7.6 mV | Pass |
| 50% Load | 19.4 mV | 14.7 mV | 20.9 mV | 9.3 mV | Pass |
| 60% Load | 19.8 mV | 15.0 mV | 20.4 mV | 12.0 mV | Pass |
| 70% Load | 17.5 mV | 14.8 mV | 19.9 mV | 11.6 mV | Pass |
| 80% Load | 18.6 mV | 15.3 mV | 21.5 mV | 14.7 mV | Pass |
| 90% Load | 17.7 mV | 16.3 mV | 17.9 mV | 17.8 mV | Pass |
| 100% Load | 26.1 mV | 17.6 mV | 19.0 mV | 25.0 mV | Pass |
| 110% Load | 26.3 mV | 18.4 mV | 20.1 mV | 22.9 mV | Pass |
| Crossload 1 | 23.8 mV | 15.7 mV | 19.2 mV | 5.5 mV | Pass |
| Crossload 2 | 15.5 mV | 18.2 mV | 15.6 mV | 5.1 mV | Pass |
| Crossload 3 | 14.7 mV | 14.7 mV | 18.9 mV | 5.1 mV | Pass |
| Crossload 4 | 25.6 mV | 17.7 mV | 19.6 mV | 11.2 mV | Pass |
The PSU didn't achieve high places in these charts, but this doesn't mean that it has a lousy ripple suppression. It is just that the competition is super-tough in this regard.
Ripple At Full Load
Ripple At 110% Load
Ripple At Cross-Load 1
Ripple At Cross-Load 4
EMC Pre-Compliance Testing – Average & Quasi-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 nearby devices.
Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other nearby devices if too high. For example, it can be the cause of increased static noise in your headphones or/and speakers.
EMI emissions are high with the average detector, and we also measured three spurs going over the limits with the peak detector. The transient filter doesn't do a great job.
MORE: Best Power Supplies
MORE: How We Test Power Supplies
MORE: All Power Supply Content
