Cougar STX 550w Non-Modular Power Supply Review

Efficiency, PFC and Voltage Regulation

Voltage Regulation

Ok, so I might be a little concerned about power supplies which don’t cost a lot. Let us, however, get to the proof in the pudding, how it fares under testing.

Starting with the voltage regulation, in what I hope is the first of many, I am pleasantly surprised. Generally speaking, the variances are both low and largely consistent. While there is definitely quite a large overpower in the -12V rail, the importance of this specific channel is very low and as such it’s not a major factor to be worried about.

Power Efficiency

The Cougar STX is 80 plus rated, but remember, it isn’t bronze. As such, while it is required to perform over 80% efficiency, anything over and above that isn’t guaranteed or even necessary to warrant the marketing. As such, in terms of efficiency, the figures are not mind-blowing. It does occasionally creep towards bronze territory, but the harder you push this power supply the more it struggles to cope.

From 40% onwards, the figures show a downward trend that ends up troughing at 100% with a test result efficiency of 80.8%. So while it fulfills the specification on the box, at full power it just barely makes it.

Power Factor Correction

The PFC rating sees another return to a more positive outlook for the Cougar STX. The figures provided in testing are exceptionally good and even in more expensive PSU’s, it’s unusual to see such high ratings in the mid-range of output. This does redeem the efficiency downturn we took in our previous test a little, but of the two, I would personally suggest that the former is the more significant results.