be quiet! Pure Power 11 FM 550W PSU Review

The be quiet! Pure Power 11 FM 550 achieves impressively high performance! It not only takes the lead from the popular Corsair RM550x, but it also surpasses the digital Cooler Master V550i Gold! The more expensive Straight Power 11 550 is also left notably behind, in overall performance. 

After testing the flagship Pure Power 11 FM unit with 1000W max power, I thought to look at the smallest one with 550W capacity. The lower capacity Pure Power 11 FM units use a platform provided by Channel Well Technology, while the two strongest ones use a HEC platform. It will be interesting to see how the smallest Pure Power 11 FM unit will fare against the competition. However, I already provided a major hint about its performance in the opening paragraph.

The be quiet! Pure Power 11 FM 550 is rated Gold by Cybenetics and 80 PLUS. It also has a Cybenetics A rating, meaning that its average noise output is within 20-25 dBA at normal operating temperatures (28-32°C). This is a true be quiet! product, considering its Cybenetics noise rating.


Cybenetics Report


Technical Specifications:
  • Manufacturer (OEM): CWT
  • Max Power: 550W
  • Cybenetics Efficiency: [115V] Gold (87-89%)
  • 80 Plus Efficiency: Gold
  • Noise: Cybenetics A (20-25 dB[A])
  • Compliance: ATX12V v2.52, EPS 2.92
  • Alternative Low Power Mode support: Yes
  • Power 12V: 550W
  • Power 5V + 3.3v: 120W
  • Power 5VSB: 15W
  • Cooling: 120mm Rifle Bearing Fan (BQ QF2-12025-MS)
  • Semi-Passive Operation: No
  • Modular Design: Yes (Fully)
  • High Power Connectors: 3x EPS (3x cables), 4x PCIe 6+2 pin (2x cables)
  • Peripheral Connectors: 14x SATA (4x cables), 4x 4-pin Molex (single cable)
  • ATX/EPS Cable Length: 550/600mm
  • Distance between SATA/ 4-pin Molex connectors: 150mm
  • In-cable capacitors: No
  • Dimensions (W x H x D): 150 mm x 85 mm x 160 mm
  • Weight: 1.56 kg (3.44 lb)
  • Warranty: 5 years

Box & Bundle

For some reason which doesn’t come to mind now, I used packaging tape, which I didn’t remove to take the photos because it would destroy the box, and I wouldn’t be able to show it to you. The protection inside is not optimal since only bubble wrap covers the product, and no packing foam is used. The latter is more expensive but provides the best possible protection.

The bundle only includes the basics, the user’s manual, a set of fixing bolts, and all cables.

Product Photos

From the moment it has a semi-passive mode, I would like to see a switch on the PSU’s front, to deactivate should I want the fan to spin constantly. Besides that, I like the exterior design, and the fan grill is not restrictive.


Modular Cables
Description Cable Count Connector Count (Total) Gauge In Cable Capacitors
ATX connector 20+4 pin (550mm) 1 1 16-18AWG No
4+4 pin EPS12V (600mm) 1 1 16AWG No
6+2 pin PCIe (500mm) 2 2 16AWG No
SATA (500mm+150mm+150mm) 1 3 18AWG No
SATA (500mm+150mm+150mm+150mm) 1 4 18AWG No
SATA (500mm+150mm) / 4-pin Molex (+150mm+150mm) / FDD (+150mm) 1 2 / 2 / 1 18-20AWG No
AC Power Cord (1400mm) – C13 coupler 1 1 18AWG

The cables are long enough for a low-capacity PSU, which is not meant for colossal chassis. Moreover, the distance between the peripheral connectors is adequate. The number of provided connectors is enough, except for the 4-pin Molex. I would like to see three 4-pin Molex instead of only two.

Protection Features

OCP (Cold @ 22°C)

12V1: 40.89A (146.04%), 11.936V
12V2: 40.99A (170.79%), 11.754V
5V: 32.2A (161%), 5.039V
3.3V: 35.6A (178%), 3.295V
5VSB: 4.6A (153.33%), 4.959V

OCP (Hot @ 42°C)

12V1: 40.59A (144.96%), 11.956V
12V2: 40.89A (170.38%), 11.778V
5V: 32A (160%), 5.040V
3.3V: 32.7A (163.5%), 3.290V
5VSB: 4.7A (156.67%), 4.959V

OPP (Cold @ 22°C)

693.42W (126.08%)

OPP (Hot @ 46°C)

693.44W (126.08%)

OTP ✓ (118°C @ 12V Heat Sink)

12V to Earth: ✓
5V to Earth: ✓
3.3V to Earth: ✓
5VSB to Earth: ✓
-12V to Earth: ✓
12V to 5V: ✓
12V to 3.3V: ✓
12V to 5VSB: ✓
12V to -12V: ✓
5V to 3.3V: ✓
5V to -12V: ✓
3.3V to 5VSB: ✓
3.3V to -12V: ✓
5VSB to -12V:✓


Accurate but lower than 16ms



Surge: MOV
Inrush: NTC Thermistor & Bypass relay

OCP is set high at 12V, especially on the second rail. Since this is a low-capacity PSU, the manufacturer wanted to ensure that there would be no shutdowns during increased power spikes. There is no point, though, for such high OCP triggering points on the minor rails, especially the 3.3V one.

The over power protection is set correctly, and the same goes for short circuit. Lastly, the power ok signal is accurate but lower than 16ms.

Part Analysis

General Data
Manufacturer (OEM) CWT
PCB Type Double Sided
Primary Side
Transient Filter 4x Y caps, 2x X caps, 2x CM chokes, 1x MOV
Inrush Protection NTC Thermistor SCK-075 (7Ohm) & Relay
Bridge Rectifier(s)
1x  GBJ1506 (600V, 15A @ 100°C)
1x Infineon IPA60R125P6 (650V, 19A @ 100°C, Rds(on): 0.125Ohm)
APFC Boost Diode
1x ON Semiconductor FFSP0665A (650V, 6A @ 153°C)
Bulk Cap(s)
2x Teapo (400V, 220uF & 270uF each or 490uF combined, 2,000h @ 85°C, LH)
Main Switchers
2x ON Semiconductor FCPF190N60E (600V, 13.1A @ 100°C, Rds(on): 0.19Ohm)
No Load Consumption FET
1x Sync Power SPN5003 (500V, 20mA @ 70°C, Rds(on): 250Ohm)
APFC Controller
Champion CM6500UNX
Resonant Controller Champion CU6901VAC
Primary side: APFC, Half-Bridge & LLC converter
Secondary side: Synchronous Rectification & DC-DC converters
Secondary Side
+12V MOSFETs 4x SG40N01Q (40V, 131A @ 100°C, Rds(on): 1.7mOhm)
5V & 3.3V DC-DC Converters: 2x UBIQ QM3054M6 (30V, 61A @ 100°C, Rds(on): 4.8mOhm) & 2x UBIQ QN3107M6N (30V, 70A @ 100°C, Rds(on): 2.6mOhm)
PWM Controller(s): uPI-Semi uP3861P
Change Over Switch 1x Sync Power SPN3006 MOSFET (30V, 57A @ 100°C, Rds(on): 5.5mOhm)
Filtering Capacitors Electrolytic: 4x Teapo (1-3,000h @ 105°C, SC), 4x Elite (2-5,000h @ 105°C, ED), 6x Elite (4-10,000h @ 105°C, EY), 1x Teapo (1-5,000h @ 105°C, SJ)
Polymer: 18x APAQ
Supervisor IC Weltrend WT7527RT (OCP, OVP, UVP, SCP, PG)
Fan Model be quiet! BQ QF2-12025-MS (120mm, 12V, 0.20A, Rifle Bearing Fan)
5VSB Circuit
1x Silan Microelectronics SVF4N65RDTR FET (650V, 2.5A @ 100°C, Rds(on): 2.7Ohm) & 1x PS1045L SBR (45V, 10A)
Standby PWM Controller On-Bright OB5282

Channel Well Technology (CWT) is the OEM of the lower-capacity Pure Power 11 FM units, and the platform is different from the one used by the RMx units. Typically for a CWT unit, there are no heatsinks on the secondary side. In contrast, the heatsinks on the primary side are small, with the only expectation of the one holding the bridge rectifiers. The PCB is large enough to allow for good airflow between the parts, and the filtering caps on the secondary side are also on the clear, so their operating temperatures will be low. The soldering quality is impeccable, but I have some complaints about the parts that be quiet! used. There is no point in using 85°C bulk caps. From an engineering perspective, these caps might not have a problem outliving the five-year warranty, but from a marketing perspective, they are a huge con. From the moment, all opponents use higher quality Japanese caps, rated at 105°C.

Load Regulation

Load regulation is within 1% on all major rails.

Ripple Suppression

Ripple suppression is great!

Transient Response

Transient response is decent for a low-capacity PSU.

Hold Up Time

The hold-up time is long, and the power ok signal is accurate.


The PSU supports Alternative Low Power Modes.

Inrush Current

Inrush current is low at 115V and on the high side with 230V.

Efficiency Normal, Light & Super-Light Loads

Efficiency is high on all load ranges.

Average Efficiency 5VSB

The 5VSB rail achieves decent efficiency, but the competition is fierce!

Vampire Power

Vampire power is bottom-low!

Average Efficiency

The average efficiency is high.

Average PF

The APFC converter does a great job!

Average Noise

The PSU is quiet, but the Straight Power 11 with similar capacity destroys all other models here, with the Corsair RM550x following.

Fan Noise & Speed Maps @ 28-32 °C

With up to 260W, there is no need for the fan to spin, even with a full load on the minor rails. The PSU passes the 30 dBA mark with more than 415W but remains in the 30-35 dBA zone.

Overall Performance

Typically the Straight Power 11 should achieve higher performance, but as you can see, this is not the case. On the contrary, the Pure Power 11 FM has a notable lead, scoring first in both 115V and 230V average performance charts. With its digital platform, even the CM V550i Gold cannot dethrone the Pure Power 11 FM unit.


be quiet! is well known for its silent operating products, and the Pure Power 11 FM with 550W max power clearly shows this. Besides silent operation, the same model also achieves top overall performance, managing to beat strong competitors from Corsair (RM550x), Cooler Master (V550i Gold), and Super Flower (Leadex III 550). Even the Straight Power 11 Platinum 550, which belongs to a higher line, is left notably behind and looks strange because the SP11 is more expensive. That said, the PSU above is the quietest in the 550W category, followed by the RM550x; the Pure Power 11 FM 550 takes over the fourth and third place, with 115V and 230V input, respectively.

be quiet! doesn’t have Corsair’s R&D resources. Despite that, it delivered an excellent 550W Gold unit which, with some more modifications, can be even better. I would ask for higher-quality bulk caps with a 105°C rating and an additional 4-pin Molex connector. They could swap the FDD connector with a 4-pin Molex one. These are not essential details and are also easy to implement, although the change of the bulk caps will affect the production cost.


Buy be quiet! Pure Power 11 FM 550W


Buy be quiet! Straight Power 11 550W


Buy Corsair RM550x


Buy Seasonic Focus GM-550


Buy Seasonic Focus GM-550


Buy Cooler Master MWE Gold 550 V2


  • Full power at 47°C
  • High overall performance
  • Efficient
  • High-performance APFC converter
  • Properly set OPP
  • Silent operation
  • Decent transient response
  • Good ripple suppression
  • Longer than 17ms hold-up time
  • Low inrush current with 115VAC
  • ALPM support
  • Option for 12VHPWR connector
  • Fully modular
  • Adequate distance between the peripheral connectors
  • Good soldering quality
  • 5-year warranty
  • High OCP on the minor rails
  • High inrush current with 230V
  • 85°C bulk caps (might be ok from an engineering perspective considering the 5-year warranty, but a marketing flaw)
  • An additional 4-pin Molex connector would be highly welcome

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2 thoughts on “be quiet! Pure Power 11 FM 550W PSU Review

  1. Hi! I’m planning to buy a PSU (for i5-13600KF / 3060 Ti / MSI B660M-A) and I’m thinking on this one (750W version), but I also consider among some other units. I would appreciate if you could help me to choose the proper one because I’m struggling with this topic!

    – Be Quiet! PURE POWER 11 FM 750W (BN319)
    – Be Quiet! PURE POWER 12 M 750W (BN343)
    – Corsair RM750e (CP-9020248)
    – Corsair RM750x (CP-9020187)
    – Corsair 750W 80+ Bronze RGB (CP-9020218)
    – Cooler Master MWE 750 Gold V2 (MPE-7501-AFAAG)

    I would like to go with a quiet unit, but also should be reliable (mainly for productivity/content creation work). The aforementioned units costs nearly the same in my country, but I found one which looks quite good and costs almost half of the others:

    – Cooler Master MWE 750 Bronze V2 (MPE-7501-ACAAB)

    I’m willing to consider this cheaper unit even if its much more loud, but I’m not sure it’s worth it compared to the above ones even for that price.

    Thanks in advance!

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