Review: be quiet! Dark Power Pro 11 850W

Running the numbers

Our testing procedures can be found at this link.

Efficiency

We're comparing the Dark Power Pro 11's numbers against another same-capacity, Platinum-rated supply in the form of the Corsair AX860i. Efficiency is a tad better on the be quiet! model.

Regulation

In terms of regulation, we're looking at just how well the supply is able to hold to the various lines. The ATX spec. has a +/- 5 per cent leeway on all but the -12V line.

Most supplies overvolt with little load and undervolt when stressed. The Dark Power Pro 11 is subjectively very, very good but, on balance, the digitally-controlled Corsair supply is a hair better in terms of regulation.

Regulation - cross-load

How about providing uneven loads that stress particular voltage rails? In the first attempt, we've put 65A on the 12V rails, and 1A on the 3.3V and 5V rails. This can actually be somewhat typical for a system heavy on graphics and CPU power. In the second, we've turned the tables and gone for 12A on both the 3.3V and 5V rails - highly unlikely in a real-world environment - and just 2A on the 12V - even more unlikely!

Hammering one part of the PSU power delivery while using just a small portion of the other can throw cheaper supplies of out kilter. There's little variation going on here; you're looking at just over two per cent from a best-to-worst-case scenario.

Ripple

The ATX v2.2 spec states that the maximum permissible ripple is 120mV for the 12V line and 50mV for others.

PSUs convert AC power into DC, but doing so requires the AC waveform to be suppressed. What we're really testing here is the quality of the supply's rectifier and any smoothing capacitors in getting rid of this unwanted up-and-down ripple - the raison d'etre of this supply.

We see similarity between the supplies that both excel in ripple suppression and easily beat the threshold mandated by the specification. The Corsair does a bit better due to its digital voltage regulation.

Temps

Platinum-rated efficiency has the ancillary benefit of producing very little heat. Being close to 95 per cent efficient at 50 per cent means the fan doesn't have much work to do in order to keep the unit working at sensible temperatures.

Fan performance

Temps are good but they mean little in isolation. Obtaining accurate noise readings is near-on impossible when the supply is connected to the Chroma test harness and dual-unit load-tester. We can test the manufacturer's quietness claims in a different way, by using an AMPROBE TMA10A anemometer placed directly over the centre of the PSU. The anemometer records the airflow being pushed/pulled from the PSU's fan. We can use a Voltcraft DT-10L RPM meter to measure the rotational speed of the fan, too.

The Dark Power Pro ranges from very quiet to quiet across a wide range of loads. High efficiencies also help keep the fan speeds low meaning it's a win-win situation if you can stomach the increased cost of opting for an 80 PLUS Platinum supply.