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Review: be quiet! Dark Power Pro 11 850W

by Tarinder Sandhu on 12 May 2015, 09:30

Quick Link: HEXUS.net/qacrdn

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Running the numbers

Our testing procedures can be found at this link.

Efficiency

Load 10pc 25pc 50pc 75pc 100pc
Efficiency - be quiet! DPP 11 86.1pc 91.0pc 94.2pc 92.6pc 91.5pc
Efficiency - Corsair AX860i 84.8pc 91.2pc 92.7pc 91.4pc 90.8pc

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.

Line/Load 3.3V 5V 12V
10 per cent - be quiet! DPP 11 +0.8pc +0.3pc +0.3pc
10 per cent - Corsair AX860i +0.6pc +0.4pc +0.5pc
50 per cent - be quiet! DPP 11 +0.6pc +0.5pc +0.7pc
50 per cent - Corsair AX860i +0.4pc +0.4pc +0.5pc
100 per cent - be quiet DPP 11 -0.7pc -0.2pc -0.4pc
100 per cent - Corsair AX 860i -0.5pc -0.3pc -0.5pc

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!

Line/Load 3.3V 5V 12V
Cross-load 12V focus - be quiet DPP 11 +1.1pc +0.8pc -0.4pc
Cross-load 12V focus - Corsair AX860i +0.8pc +0.9pc -0.5pc
Cross-load 3.3V/5V focus- be quiet DPP 11 -1.5pc -0.7pc +0.3pc
Cross-load 3.3V/5V focus - Corsair AX860i -1.3pc -0.9pc +0.5pc

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

Line/Load (mv - p-p max) 3.3V 5V 12V
10 per cent - be quiet DPP 11 10mV 15mV 25mV
10 per cent - Corsair AX860i 10mV 15mV 15mV
50 per cent - be quiet DPP 11 15mV 15mV 25mV
50 per cent - Corsair AX860i 15mV 15mV 20mV
100 per cent - be quiet DPP 11 15mV 20mV 30mV
100 per cent - Corsair AX860i 15mV 20mV 25mV

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

Temperatures Intake Exhaust
10 per cent - be quiet DPP 11 28°C 31°C
10 per cent - Corsair AX860i 28°C 33°C
50 per cent - be quiet DPP 11 31°C 34°C
50 per cent - Corsair AX860i 32°C 35°C
100 per cent - be quiet DPP 11 39°C 42°C
100 per cent - Corsair AX860i 37°C 39°C

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.

Load Fan RPM Airflow Noise
10 per cent - be quiet DPP 11 300rpm 15cfm Very quiet
10 per cent - Corsair AX860i 0rpm 0cfm Silent
50 per cent - be quiet DPP 11 520rpm 20cfm Very quiet
50 per cent - Corsair AX860i 610rpm 20cfm Very quiet
100 per cent - be quiet DPP 11 1,100rpm 45cfm Quiet
100 per cent - Corsair AX860i 1,450rpm 55cfm Quiet

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.