Connected to my APC SmartUPS SC 620, the AX1200 was stable at loads up to 418 watts when powered by the mains but the UPS reported overload and shut down immediately after the pair tried to switch to the UPS batteries.
Output Voltage Stability
The cross-load diagram is similar to the Antec’s except that it’s now the +5V rather than +3.3V voltage that acts as the weak link.
The +12V voltage is almost ideal, always staying within 2% of the nominal value. The +3.3V voltage deflects by more than 3% only when there’s very high load on both the +3.3V and +12V rails.
The +5V voltage is the most unstable of all. It deflects by 4% from its default level in the typical load range of that power rail when there’s also high load on the +12V rail.
Output Voltage Ripple
As promised by the manufacturer, the high-voltage ripple at full load is very low and meets the requirements of the industry standard.
We can see some voltage spikes on the +12V rail at the double frequency of the power mains. This ripple is within the permissible limits but spoils the good impression from the previous diagram.
Temperature and Noise
The AX1200 is cooled by a 7-blade Yate Loon fan (D14BH-12 part number, 140mm, 2800 RPM).
The good news is that the fan is never close to its maximum 2800 RPM even at full load. The highest speed it can reach in this PSU is about 1700 RPM.
The bad news is that it starts out at a rather high speed of 1300 RPM and accelerates right away.
As a result, the fan is going to be audible even when the computer is idle. This can hardly be made up for by the fact that the AX1200 is quite good in terms of noisiness at full load (compared to same-class products).
Efficiency and Power Factor
As opposed to the Antec, the Corsair PSU gives no reason to question its 80+Gold certification. It is 88.9%, 90.3% and 87% efficient at loads of 20%, 50% and 100%.
Its active PFC device works somewhat better than in average PSUs, keeping the power factor above 99% through the larger part of the load range and reaching 99.8% at the maximum.
+5V Standby Source
The standby source copes with its job but the voltage drop is noticeable at near-maximum load.
The Corsair AX1200 features good electrical parameters and handy modular cables. It is not very loud at high loads but its fan is audible even in idle mode.