Alas, the cross-load diagram looks bad again. The +5V voltage is set too high and the +12V voltage is not very stable.

At a load of 450W the voltage ripple on the PSU’s outputs was 31 millivolts on the +5V rail and 71 millivolts on the +12V rail.

I measured the speed of the PSU fans at the two extreme positions of the manual control. This only affects the speed of the back-panel fan, but the automatically adjusted speed of the second fan also changes because the PSU temperature depends on the airflow intensity.

This power supply is rather quiet at the min fan speed. The second fan is faster than 2000rpm, but it is hidden deep inside in an assembled computer and is not very audible.

When the manual control is set at its maximum position, the fan speed exceeds 4000rpm. There’s no talking about silence now, the PSU just roars loudly. The minor decrease in the speed of the second fan is but a poor compensation for that.

The PSU’s efficiency is a little lower than that of the previous model. The power factor is 0.98 thanks to active power factor correction.

Generally speaking, there are only external differences between the Butterfly W0020 and the above-described W0009. I mean the exterior design and the accessories. The Butterfly comes with a blower and a fan speed controller (for two fans which must come from Thermaltake and must explicitly support this controller because it is attached via a separate connector) and is highlighted with blinking three-colored LEDs. From the technical viewpoint, it is an obsolete ATX12V 1.3 unit a modern computer can only get about half the declared wattage from – after that the PSU’s +12V power rail will get overloaded. This lack of power is also aggravated by the lack of stability of the output voltages. So, you should better turn to other PSU models, even to other models from Thermaltake. The system blower and the multicolored LEDs can be purchased separately whenever you want them.