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[nextpage title=”Introduction”]
The brand bequiet! belongs to the German distributor Listan. This company has released several power supplies with the 80 Plus Gold certification, under the Straight Power E9 series. Five of them (400 W, 450 W, 500 W, 600 W, and 700 W) don’t have a modular cabling system, while three of them do (480 W, 580 W, and 680 W). These models carry the letters “CM” for “Cable Management.” Let’s see if the 680 W model is a good option.
The bequiet! Straight Power E9 CM 680 W power supply is manufactured by FSP, based on the same platform as the FSP Aurum CM Gold.
Figure 1: The bequiet! Straight Power E9 CM 680 W power supply
Figure 2: The bequiet! Straight Power E9 CM 680 W power supply
The bequiet! Straight Power E9 CM 680 W is 6.3” (160 mm) deep, using a 135 mm fluid dynamic bearing fan on its bottom (bequiet! Silent Wings E9).
As mentioned, this unit has a modular cabling system with seven connectors, two for video cards, one for the ATX/EPS12V power cable, and four for peripheral and SATA power cables. Only the main motherboard cable is permanently attached to the power supply. This power supply comes with the following cables:
- Main motherboard cable with a 20/24-pin connector, 21.6” (55 cm) long, permanently attached to the power supply
- One cable with two ATX12V connectors that together form an EPS12V connector, 21.6” (55 cm) long, modular cabling system
- Four cables with one six/eight-pin connector for video cards (each pair is connected to a single connector on the power supply side), 21.6” (55 cm) long, modular cabling system
- One cable with four SATA power connectors, 21.6” (55 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
- One cable with three SATA power connectors, 21.6” (55 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
- One cable with four standard peripheral power connectors, 22.4” (57 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
- One cable with two SATA power connectors, two standard peripheral power connectors, and one floppy disk drive power connector, 21.6” (55 cm) to the first connector, 5.9” (15 cm) between connectors, modular cabling system
All wires are 18 AWG, which is the minimum recommended gauge.
The cable configuration is excellent for a 680 W power supply, with four video card power connectors and nine SATA power connectors.
Figure 3: Cables
Let’s now take an in-depth look inside this power supply.
[nextpage title=”A Look Inside the bequiet! Straight Power E9 CM 680 W”]
We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our “Anatomy of Switching Power Supplies” tutorial to understand how a power supply works and to compare this power supply to others.
On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used. As already mentioned, this power supply is based on the FSP Aurum CM Gold platform.
Figure 4: Top view
Figure 5: Front quarter view
Figure 6: Rear quarter view
Figure 7: The printed circuit board
[nextpage title=”Transient Filtering Stage”]
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.
In this stage, the bequiet! Straight Power E9 CM 680 W power supply is impeccable, with two Y capacitors, one X capacitor, and one ferrite coil more than the minimum required. According to FSP, because of the design used in this power supply, an MOV is not required.
Figure 8: Transient filtering stage (part 1)
Figure 9: Transient filtering stage (part 2)
On the next page, we will have a more detailed discussion about the components used in the bequiet! Straight Power E9 CM 680 W.
[nextpage title=”Primary Analysis”]
On this page we will take an in-depth look at the primary stage of the bequiet! Straight Power E9 CM 680 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.
This power supply uses two GBU1006 rectifying bridges, which are attached to an individual heatsink. Each bridge supports up to 10 A at 100° C, so in theory, you would be able to pull up to 2,300 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,840 W without burning themselves out. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply. It is interesting to note that both the FSP Aurum Gold 700 W and the Aurum CM Gold 750 W use only one of these bridges here.
Figure 10: Rectifying bridges
The active PFC circuit uses two IPB60R165CP MOSFETs, which are capable of delivering up to 21 A at 25° C or 13 A at 100° C in continuous mode (note the difference temperature makes), or up to 61 A in pulse mode at 25° C, each. These transistors present a 165 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power, and the power supply will achieve a higher efficiency. These are the same transistors used in the FSP Aurum Gold 700 W and the Aurum CM Gold 750 W.
The output of the active PFC circuit is filtered by a 390 µF x 420 V electrolytic capacitor from CapXon, labeled at 85° C. The two FSP models to which we are comparing this unit use Japanese capacitors labeled at 105° C.
In the switching section, the bequiet! Straight Power E9 CM 680 W uses FSP’s design of choice for 80 Plus Gold units, called active clamp reset forward. The switching transistor is an SPA17N80C3 MOSFET, which is capable of delivering up to 17 A at 25° C or 11 A at 100° C in continuous mode (note the difference temperature makes), or up to 51 A at 25° C in pulse mode. This transistor presents a 290 mΩ RDS(on). A second transistor (resetting transistor) is used to turn off the switching transistor and is controlled from the secondary side. The transistor used for this function is an FQPF3N80C. This is exactly the same configuration used in the FSP Aurum Gold 700 W and the Aurum CM Gold 750 W.
Figure 11: Switching transistor, resetting transistor, active PFC diode and active PFC transistors
The primary is managed by a custom-made PFC/PWM controller called FSP6600. Since this is a custom integrated circuit, no datasheet is available for it.
Figure 12: Active PFC/PWM controller
Let’s now take a look at the secondary of this power supply.
[nextpage title=”Secondary Analysis”]
The bequiet! Straight Power E9 CM 680 W uses a synchronous design in its secondary, meaning that the diodes were replaced with transistors in order to increase efficiency.
The +12 V output is rectified using two IRLB3036 MOSFETs, each one capable of handling up to 270 A at 25° C or up to 190 A at 100° C in continuous mode, or up to 1,100 A at 25° C in pulse mode. This translates into a maximum theoretical current of 271 A at 100° C or 3,257 W!
Figure 13: +12 V transistors
The +5 V and +3.3 V outputs share the same circuitry and are rectified by two IPD031N03L MOSFETs – 90 A at 100° C in continuous mode and 400 A at 25° C in pulse mode, 3.1 mΩ RDS(on) – and two IPD050N03L MOSFETs. The four transistors are located on the solder side of the printed circuit board.
Figure 14: The +5 V and +3.3 V transistors
The secondary transistors are controlled by an FSP6601, another proprietary chip from FSP.
Figure 15: Synchronous controller
The secondary is monitored by a WT7579 integrated circuit, which is manufactured exclusively for FSP. This chip supports over voltage (OVP), under voltage (UVP), overcurrent (OCP), and over temperature (OTP) protections. There are four +12 V over current protection (OCP) channels, matching the number of +12 V rails advertised by the manufacturer.
Figure 16: Monitoring circuit
All electrolytic capacitors used in the secondary are from CapXon and labeled at 105° C, as usual.
In summary, the secondary of the bequiet! Straight Power E9 CM 680 W is identical to the secondary of the FSP Aurum Gold 700 W and the Aurum CM Gold 750 W, except that the models sold by FSP use Japanese capacitors.
[nextpage title=”Power Distribution”]
Figure 17 shows the power supply label containing all the power specs.
Figure 17: Power supply label
As you can see, the manufacturer lists this unit as having four +12 V rails. Analyzing the circuit
, we could clearly see four “shunts” (current sensors), matching the number of rails advertised by the manufacturer. See Figure 18. Click here for a more detailed explanation.
Figure 18: Shunts
The available +12 V rails are distributed as follows:
- +12V1 (solid yellow wire): Main motherboard cable, SATA and peripheral power connectors
- +12V2 (yellow connector of the modular cabling system): The ATX12V/EPS12V cable
- +12V3 (green connector of the modular cabling system): The video card power cables that are installed on the green connector of the modular cabling system
- +12V4 (red connector of the modular cabling system): The video card power cables that are installed on the red connector of the modular cabling system
This distribution is perfect, as it separates the CPU and the video card power cables on individual rails. However, if you have only one video card with two power connectors, we recommend that you use one cable from each available connector instead of using the two cables available on one of the connectors.
Let’s now see if this power supply can really deliver 680 W.
[nextpage title=”Load Tests”]
We conducted several tests with this power supply, as described in the article, “Hardware Secrets Power Supply Test Methodology.”
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching the behavior of the reviewed unit under each load. In the table below, we list the load patterns we used and the results for each load.
If you add all the powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, the +12VA input was connected to the power supply +12V1 and +12V3 rails, while the +12VB input was connected to the power supply +12V2 rail.
During test five, we couldn’t pull more than 21 A from the power supply +12V2 rail, as the over current protection (OCP) kicked in. That is the reason the current distribution between the two +12 V inputs may look unbalanced in test five.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 5 A (60 W) | 10 A (120 W) | 15 A (180 W) | 20 A (240 W) | 28.5 A (342 W) |
| +12VB | 5 A (60 W) | 10 A (120 W) | 15 A (180 W) | 20 A (240 W) | 21 A (252 W) |
| +5 V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) |
| +5VSB | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 W) | 3 A (15 W) |
| -12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
| Total | 137.3 W | 275.8 W | 412.3 W | 535.2 W | 678.4 W |
| % Max Load | 20.2% | 40.6% | 60.6% | 78.7% | 99.8% |
| Room Temp. | 44.9° C | 44.9° C | 46.2° C | 45.8° C | 45.6° C |
| PSU Temp. | 48.2° C | 48.6° C | 49.2° C | 49.9° C | 48.4° C |
| Voltage Regulation | Pass | Pass | Pass | Fail at +3.3 V | Fail at +3.3 V |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 151.4 W | 301.7 W | 457.8 W | 604.8 W | 787.0 W |
| Efficiency | 90.7% | 91.4% | 90.1% | 88.5% | 86.2% |
| AC Voltage | 116.1 V | 114.5 V | 112.9 V | 111.3 V | 108.8 V |
| Power Factor | 0.982 | 0.994 | 0.998 | 0.998 | 0.999 |
| Final Result | Pass | Pass | Pass | Fail | Fail |
The bequiet! Straight Power E9 CM 680 W can really deliver its labeled wattage at high temperatures.
Efficiency was between 86.2% and 91.4% during our tests. The 80 Plus Gold certification promises 87% minimum efficiency at full load. This little difference happens because the 80 Plus tests are conducted at 23° C, and we test power supplies at a temperature of at least 45° C, and efficiency drops with temperature.
Voltage regulation was an issue, with the +3.3 V output dropping below the minimum allowed during tests four and five. See table below. The ATX12V specification states that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | ≤ 3% | ≤ 3% | ≤ 3% | ≤ 3% | ≤ 3% |
| +12VB | ≤ 3% | ≤ 3% | ≤ 3% | ≤ 3% | ≤ 3% |
| +5 V | ≤ 3% | ≤ 3% | ≤ 3% | ≤ 3% | ≤ 3% |
| +3.3 V | ≤ 3% | ≤ 3% | +3.14 V | +3.11 V | +3.12 V |
| +5VSB | ≤ 3% | ≤ 3% | ≤ 3% | +4.85 V | +4.82 V |
| -12 V | ≤ 3% | ≤ 3% | -12.45 V | -12.53 V | -12.53 V |
Let’s discuss the ripple and noise levels on the next page.
[nextpage title=”Ripple and Noise Tests”]
Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.
The bequiet! Straight Power E9 CM 680 W provided ripple and noise levels within the proper range, although they were too high during test five for us to consider this unit “flawless.”
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 25.6 mV | 28.2 mV | 36.8 mV | 51.4 mV | 78.4 mV |
| +12VB | 30.4 mV | 33.8 mV | 43.2 mV | 57.6 mV | 85.6 mV |
| +5 V | 14.2 mV | 15.4 mV | 18.6 mV | 2 3.0 mV |
40.2 mV |
| +3.3 V | 21.4 mV | 24.4 mV | 27.2 mV | 29.4 mV | 31.4 mV |
| +5VSB | 12.4 mV | 7.8 mV | 8.2 mV | 10.4 mV | 10.4 mV |
| -12 V | 53.2 mV | 59.4 mV | 64.4 mV | 71.2 mV | 91.6 mV |
Below you can see the waveforms of the outputs during test five.
Figure 19: +12VA input from load tester during test five at 678.4 W (78.4 mV)
Figure 20: +12VB input from load tester during test five at 678.4 W (85.6 mV)
Figure 21: +5V rail during test five at 678.4 W (40.2 mV)
Figure 22: +3.3 V rail during test five at 678.4 W (31.4 mV)
Let’s see if we can pull more than 680 W from this unit.
[nextpage title=”Overload Tests”]
Below you can see the maximum we could pull from this power supply. We couldn’t pull more than 21 A from the power supply +12V2 rail because the over current protection would kick in. During this extreme configuration, noise and ripple levels were way above the maximum allowed (167.4 mV at +12VA, 172.4 mV at +12VB, 80.8 mV at +5 V, 52.4 mV at +3.3 V, and 176.6 mV at -12 V), and the +12VA, +5 V, and +3.3 V outputs were below the minimum allowed, at +11.39 V, +4.58 V, and +3.03 V, respectively.
| Input | Overload Test |
| +12VA | 33 A (396 W) |
| +12VB | 21 A (252 W) |
| +5 V | 20 A (100 W) |
| +3.3 V | 20 A (66 W) |
| +5VSB | 3 A (15 W) |
| -12 V | 0.5 A (6 W) |
| Total | 802.4 W |
| % Max Load | 118.0% |
| Room Temp. | 46.4° C |
| PSU Temp. | 47.1° C |
| AC Power | 979 W |
| Efficiency | 82.0% |
| AC Voltage | 106.2 V |
| Power Factor | 0.994 |
[nextpage title=”Main Specifications”]
The main specifications for the bequiet! Straight Power E9 CM 680 W power supply include:
- Standards: ATX12V 2.31 and EPS12V 2.92
- Nominal labeled power: 680 W continuous, 750 W peak at 40° C
- Measured maximum power: 802.4 W at 46.4° C
- Labeled efficiency: 80 Plus Gold certification
- Measured efficiency: Between 86.2% and 91.4%, at 115 V (nominal, see complete results for actual voltage)
- Active PFC: Yes
- Modular Cabling System: Yes
- Motherboard Power Connectors: One 20/24-pin connector permanently attached to the power supply and two ATX12V connectors that together form an EPS12V connector on the modular cabling system
- Video Card Power Connectors: Four six/eight-pin connectors on four cables (each pair of cables is connected to the same connector on the power supply end), modular cabling system
- SATA Power Connectors: Nine on three cables, modular cabling system
- Peripheral Power Connectors: Six on two cables, modular cabling system
- Floppy Disk Drive Power Connectors: One
- Protections (as listed by the manufacturer): Over current (OCP), over voltage (OVP), under voltage (UVP), over power (OPP), over temperature (OTP), and short circuit (SCP)
- Are the above protections really available? Yes.
- Warranty: Five years
- Real Manufacturer: FSP
- More Information: https://www.be-quiet.net
- MSRP in Europe: € 125.00
[nextpage title=”Conclusions”]
The bequiet! Straight Power E9 CM 680 W is based on the FSP Aurum Gold platform, with a few modifications. It uses a quieter fan, utilizes two rectifying bridges in the primary instead of only one, the ATX12V/EPS12V connector was moved to the modular cabling system, and it has a better cable configuration. However, the original FSP models use better electrolytic capacitors (made in Japan and labeled at 105° C).
The efficiency of this unit is top-notch, between 86.2% and 91.4%. Noise and ripple levels, although inside the allowed range, were too high during our full load test to consider this unit “perfect.” The main drawback of this unit was voltage regulation, with the +3.3 V output presenting voltage below the minimum allowed during two of our five tests. We believe that this bad performance was caused by the power supply’s high internal temperature during our tests, as the manufacturer decided to use a fan that prioritizes silence over performance.