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Be Quiet! Dark Power Pro 11 1200W PSU Review

be quiet! says it's committed to building silent products, including the company's top PSU line, the Dark Power Pro 11. In this review, we will put the 1200 W Dark Power Pro 11 model to the test, which promises good performance and silent operation.

Load Regulation, Hold-Up Time And Inrush Current

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

Load Regulation testing is detailed here.

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Hold-Up Time

Our hold-up time tests are described in detail here.

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The hold-up time that our equipment measured was lower than 16 ms, so the PSU failed in this test.

Inrush Current

For details on our inrush current testing, please click here.

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The registered inrush current was adequate, especially for a 1.2 kW unit. This is great news, but we would prefer to see a little higher inrush current, which could be possible if be quiet! used higher capacity hold-up caps, instead of a hold-up time lower than 16 ms.

Load Regulation And Efficiency Measurements

The first set of tests reveals the stability of the voltage rails and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.10A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails.

Test12V5V3.3V5VSBPower(DC/AC)EfficiencyFan SpeedFan NoiseTemp(In/Out)PF/AC Volts
18.176A1.983A1.959A0.980A119.74W86.06%510 RPM21.1 dBA39.15°C0.979
217.370A2.980A2.948A1.182A239.38W90.00%565 RPM24.3 dBA40.30°C0.995
326.982A3.496A3.464A1.385A359.70W91.09%780 RPM30.1 dBA41.09°C0.996
436.587A3.994A3.952A1.585A479.47W91.31%1015 RPM33.9 dBA41.74°C0.997
545.872A5.007A4.955A1.789A599.36W91.18%1270 RPM42.1 dBA41.93°C0.998
655.168A6.026A5.968A1.995A719.14W90.49%1610 RPM43.7 dBA42.61°C0.998
764.499A7.040A6.983A2.201A839.03W89.98%1800 RPM46.4 dBA43.41°C0.998
873.857A8.075A8.008A2.411A959.07W89.28%1800 RPM46.4 dBA44.10°C0.998
983.672A8.595A8.543A2.414A1079.03W88.60%1800 RPM46.4 dBA45.07°C0.998
1093.246A9.120A9.057A3.035A1198.83W87.67%1800 RPM46.4 dBA47.27°C0.998
11103.456A9.133A9.076A3.040A1318.74W86.81%1800 RPM46.4 dBA48.65°C0.998
CL10.097A18.022A18.003A0.000A149.28W82.87%1640 RPM44.0 dBA44.83°C0.986
CL296.981A1.002A1.003A1.001A1202.15W88.12%1825 RPM46.5 dBA47.23°C0.998

In the tough conditions that we conducted our tests in, the PSU didn't meet all the requirements of the 80 Plus Platinum certification. Actually, the unit managed to hit the target only with 20 percent load, which shows 90 percent efficiency. With 50 percent of its max-rated capacity load and with a full load, efficiency was significantly lower than the levels that the Platinum certification sets (92 percent and 89 percent, respectively). Nonetheless, in both cases the efficiency difference in the Platinum levels was within 1 percent, so we can give this PSU a pass, considering that ECOVA conducts their tests at only 23 C (73 F), while we conducted our tests at a much higher ambient temperature. As the operating temperature rises, the resistance of several components, including the FETs, increases leading to significant energy losses. On the other hand, the resistance of diodes, including components like SBRs (Schottky Barrier Diodes) and bridge rectifiers, actually lowers at higher temperatures. However, this PSU only uses FETs for the regulation of its outputs.

The Dark Power P11-1200’s load regulation performance wasn't able to meet its competition, although it was decent overall. In this price range the competition is fierce, offering very high performance. On the other hand, the be quiet! PSU delivered its full power more effortlessly than other unit, and at very high operating temperatures that were close to 49 C (120 F) during the 110 percent load test. Besides that, up to the 40 percent load test, the unit's noise was very low and in the worst-case scenario it didn't exceed 47 dBA. For a 1.2 kW PSU, the noise output is at very low levels, also given the tough conditions we applied during these tests.

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.