Introduction

I would like to thank Listan for supplying me with the unit for review.

The be quiet! power supplies are a brand of Listan, which is a big distributor of computer hardware, originally from Germany. Founded in 2000 the company has developed into one of the leading distributors in Europe. At the company head offices in Glinde (near Hamburg/Germany), the staff of 50 look after over 4,000 resellers in 24 countries.

Specifications from manufacturer

TOP EFFICIENCY

extremely high efficiency rate of up to 84%
active PFC with PF of up to 0.99:
stabilisation and improvement of the output currents.
the Dark Power Pro uses no power when it is switched off (0W)
manufactured strictly according to RoHS guidelines

THERMO CONTROL
Fan follow-up control (ECASO) protects sensitive hardware such as graphic cards or hard drives effectively from overheating. The power supply fan and the fans connected to the power supply are supplied with power for 3 minutes after shutting down. The thermal electronics regulates the rotational speed of the power supply fan and of the 3 housing fans connected directly to the power supply. The speed indicator signal of the power supply fan can be read out over the mainboard.

SERVICE PLUS

3 year guarantee, 1 year more than legally required.
ENGLISH HOTLINE Service Hotline: +49 40 736 76 86 – 559
and Email Support: service@be-quiet.com

HIGH CONNECTIVITY

flexible cable management (up to 19 cable strands, 17 of them removable)
high quality processing, with nylon weave cable sheath
greatest compatibility with available mainboard technologies
four separate 12V circuits ensure an independent power supply of the CPU
the use of SLI, CrossFire systems and Quad SLI solutions is made possible by four
6-pin PCIe VGA connectors!
P8 connection for dual server mainboards
12 x SATA connections
Forward looking for the next generation of graphic cards

Packaging

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The black package is big and very heavy. When you purchase it you sure have a feeling that you got something for your money. The picture on the back of the package is very useful, it tells you the exact cable lengths of this power supply.

Box contents:

Power supply unit
Power Cord
Cables
Cable fastener, zip ties
Screw package
Instruction Manual
24 pin to 20 pin power adapter
Caps to cover unused connectors

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<table class="resulttable" border="1" cellspacing="0" cellpadding="5">
<tr>
<th rowspan="2">Connectors</th>
<th align="center">Main Power</th>
<th align="center">5.25"</th>
<th align="center">Floppy</th>
<th align="center">4 Pin CPU</th>
<th align="center">SerialATA</th>
<th align="center">PCI-E Aux Power</th>
</tr>
<tr>
<td align="center">ATX 24 Pin</td>
<td align="center">up to 14 </td>
<td align="center">up to 1 </td>
<td align="center">1 + up to 2 </td>
<td align="center">up to 12 </td>
<td align="center">up to 4 </td>
</tr>
</table>

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The package contains an extra box that has all the cables neatly arranged in it.

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The PSU itself is wrapped safely in bubble wrap to make sure there are no scratches from the transport.

The PSU

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A very useful feature of the DarkPower Pro 750W is that it is modular in design. This means that you need to attach only as many cords as you need to connect all your components. This reduces the cable mess in your case a lot. I really like that the ATX power cable does not use a modular connector. You always need this cable, so having it modular would introduce some unwanted losses in voltage quality. These losses are very small, but every little bit helps.

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The paintjob on the PSU is a dark brushed metal style with clear lacquer on top of it. When handling it it is easy to get fingerprints on the surface, but these can be wiped away with your hand easily.

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There is no switch to select the input voltage between 110V and 220V. Circuitry inside the PSU automatically detects the supply voltage.

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Here you can see the brushed look very well. The surface is still completely smooth because of the clear lacquer coating.

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This little 24 pin to 20 pin ATX power connector is included. Usually you have an adapter that uses a cable in between, adding some unnecesarry wiring in your case which is ugly and hard to hide. I must say this is a very impressive solution.

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Depending on your motherboard you are going to use a 4-pin or 8-pin connector to supply the CPU voltage to the motherboard. The 4-pin cable is attached fixed like the ATX 24 pin cable. If you need the 8-pin connector you plug an extra cable in at the back of the PSU, the 4-pin cable will remain unused then.

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The PCI-Express video card power cables have some components in them that stabilize the supply voltage. This is the first time I see this on a PSU, usually you have to buy extra cables to do that. Inside you will usually find a ferrite, a capacitor and maybe a coil. Measuring the benefits of this is extremely hard. Even if there is a visible difference in the supplied voltage to the video card there is almost no way to determine the effect of it, since the videocard has a power regulation circuitry on board which is designed to handle unclean voltages. Still, this is a nice feature that may help your power stability.

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These small caps can be used to cover the unused plugs on connected cables. For example if you use only one SATA of a cable. The idea is to prevent short circuits. With the design of the connectors I see no need for additional protection. It would have been more useful if they could be used to cover the unused connectors on the power supply to make it look cleaner.

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The fan is made for be Quiet! by Sanyo Denki and is very quiet.

PSU Inside

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To open the PSU you need to break a paper seal which covers one of the four screws - warranty gone!

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The inside looks well cleaned up, all cables are attached safely with zip ties.

Test Equipment

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The PSU is connected to an APC SmartUPS which supplies clean 220V input.
AC current is measured using a Peaktech 4010 desktop RS232 multimeter with 0.02A accuracy.
To measure DC output voltages of the PSU we use a Keithley 2700 6.5 digit data acquisition system. All three input voltages are measured at the same time using a solid state switching system.
Power Factor is measured using a generic Power Efficiency Meter.
Measurements for Ripple Voltage were obtained using a 100 MHz Tektronix TDS224 Digital Storage Oscilloscope.

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Fan noise measurements are performed with an IEC Type 2 Sound level meter and this setup.
It consists of three high-power resistors and a Socket A motherboard. The motherboard creates a small load which makes sure the PSU turns on (some PSUs require a minimum load). Since there is no hardware installed in the motherboard, its power draw is negligible. The three resistors create a static load of 320W (120W @ 12V + 50W @ 5V + 150W @ 12V) - a typical high-performance system. This setup is also used to determine the power conversion efficiency of the PSU.

Performance

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<table class="resulttable" border="1" cellspacing="0" cellpadding="5">
<tr>
<th colspan="11">be quiet! DarkPower 750W - BQT P6-PRO 750W </th>
</tr>
<tr>
<th>AC Input</th>
<td colspan="10">100V-240V, 12A-6A, 50 Hz</td>
</tr>
<tr>
<th>DC Voltage</th>
<td align="center">+3.3V</td>
<td align="center">+5V</td>
<td align="center">+12V1</td>
<td align="center">+12V2</td>
<td align="center">+12V3</td>
<td align="center">+12V4</td>
<td align="center">-12V</td>
<td align="center">+5VSB</td>
</tr>
<tr>
<th rowspan="3">Max. Output</th>
<td align="center">24A</td>
<td align="center">30A</td>
<td align="center">20A</td>
<td align="center">20A</td>
<td align="center">20A</td>
<td align="center">20A</td>
<td align="center">0.8A</td>
<td align="center">3A</td>
</tr>
<tr>
<td colspan="2" align="center">170 W </td>
<td colspan="4" align="center">600 W </td>
<td colspan="2" align="center">20W</td>
</tr>
<tr>
<td colspan="8" align="center">750 W </td>
</tr>
</table>

Wow! That's some massive power delivery capability. 20 Amps on each of the four rails should be enough for any video card that will come out in the near future. It is definitely enough for G80 and R600.

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Tested on: AMD Athlon64 3000+ @ 2000 MHz, ABIT AT8, Radeon X1900 XTX + Radeon X1900 XTX Crossfire, 2x 512 MB DDR400, WD Raptor 36 GB.

All voltages are very stable, especially the 12V line, which goes to almost exactly 12.0V under load. The 3.3V line seems to be fluctuating a bit, but since no vital components need that voltage it does not matter at all. Nowadays all components draw most of their supply voltage from the 12V line.

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Above image shows the Ripple Voltage measurement (5 mV per vertical division, 5uS per horizontal division). With 17 mV from top to bottom, the result is only about average. Ripple voltage was measured on the 12V line at idle.

<table class="resulttable" border="1" cellspacing="0" cellpadding="5">
<tr>
<th>Standard deviation 12V</th>

<td align="right">50.62</td>
</tr>
<tr>
<th>Standard deviation 5V</th>
<td align="right">10.92</td>
</tr>
<tr>
<th>Standard deviation 3.3V</th>
<td align="right">13.70</td>
</tr>
<tr>
<th>Power Factor</th>
<td align="right">0.96</td>
</tr>
<tr>
<th>Ripple Voltage 12V</th>
<td align="right">17 mV</td>
</tr>
<tr>
<th>Power Efficiency</th>
<td align="right">78% (320W:413W)</td>
</tr>
</table>

Standard deviation is a statistical term, which tells how far away from the average the measurements are. In other words it's the average of the average.
A large standard deviation indicates that the data points are far from the average and a small standard deviation indicates that they are close within the average.

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With an efficiency of 78% the Dark Power Pro claims the title of being the most energy efficient PSU we tested so far.

10% of efficiency come down to a yearly difference of $4.08 in power cost. This is assuming $ 0.10 per kWh, which is an accepted average value for power cost in the United States. We assumed 8 hours of PC usage per day, 5 days a week at 200W system average power draw.

Fan Noise

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According to be quiet! there is a temperature controlled fan on the DarkPower Pro 750W. But since the unit is so efficient, it barely gets warm, even with the fan running at the slowest speed. That's why there is no fan speed change between idle and load.

Value and Conclusion

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$190 is going to rip a big hole into your pocket. But if you need this PSU for your system, your hardware will have cost a lot more than that.

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Four PCI-E video card connectors
Modular
Four 12V rails with massive 20 A each
Good voltage stability
Very well thought out modularity design
All cables are sleeved
Temperature controlled fan
Quiet
Huge number of connectors available
Fan connectors included

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High Price

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<tr><th>9.4</th>
<td>The be quiet! Dark Power Pro 750W has been designed very well in every aspect I can think of. It offers four PCI-Express video card connectors for all your future video card configurations. Remember, the GeForce 8800 GTX in SLI needs a total of four connectors (two for each card). Even with a power hungry Crossfire system connected, all lines were stable. What is really impressive is the high efficiency of about 77% on our testbed, making this the most efficient power supply that we tested so far. Since the efficiency is high, there is also very little heat coming from the PSU which means that the fan can run slower. This results in a very quiet power supply, even under load. Be Quiet! advertises the fan to be temperature controlled, in our testing the fan always remained at its minimum speed.<br />
The whole modularity concept worked out very well for the Dark Power Pro 750W. It offers an insane number of connectors, total over 30! With a traditional PSU this would be a major cable mess, with the Dark Power Pro you just connect what you need. The included short cables that have only one 5.25" connector on them comes in very handy when building mininmal system configurations.<br />
Even though the be quiet! Dark Power Pro 750W does not come cheap it will sure last you for more than one PC generation you will have.
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