be quiet! Straight Power 11 550W Platinum Power Supply Review

The new Straight Power 11 model with 550W max power is now certified as 80 PLUS Platinum and features a dead silent operation.

be quiet! Straight Power 11 550W Platinum
(Image: © Shutterstock, be quiet!)

Tom's Hardware Verdict

The Straight Power 11 Platinum model with 550W max power is silent, achieves satisfactory overall performance and uses quality parts. The performance difference with the previous model is small, though.


  • +

    Full power at 45 degrees Celsius

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    Silent operation

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    High-quality components

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    Long hold-up time

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    Fully modular

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    Compatible with the alternative sleep mode

  • +

    Adequate distance between the peripheral connectors


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    Low overall performance difference with the previous model

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    The protection features are not configured correctly

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    No bypass relay in the inrush current protection circuit

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    High Vampire Power

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    Efficiency at 5VSB is much lower compared to the previous model

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    Lower than 70% efficiency with 2% load

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    Not compatible with the alternative sleep mode

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The new Straight Power 11 Platinum model with 550W max power has a small overall performance difference with the previous Gold model, despite the new platform that FSP used. To make matters worse, it uses an inferior 5VSB circuit, with notably lower efficiency levels. The competition is hard with the Fractal Design Ion+ 560P and the Seasonic Focus Platinum model with similar capacity being better choices. The Corsair RM550x, our best power supply pick in the 550W category, also achieves higher performance despite the lower efficiency certification in the 80 PLUS scheme (in Cybenetics, both the RM550x and the Straight Power 11 Platinum 550 have the same efficiency rating, ETA-A).

There are two Straight Power (SP) 11 lines in be quiet's portfolio right now, one with Gold-certified members and capacities ranging from 450W to 1000W and one with Platinum models and 550W up to 1200W max power. We don't know, yet, if the older Straight Power 11 line will remain in the market, or will be replaced by the new one. For the moment, both are listed on the brand's official page.

Besides the different min and max capacities of their models and the efficiency certifications, another significant difference between the SP Gold and Platinum lines is the new platform that the new models utilize. The OEM remains FSP, which uses a fresh design featuring a full-bridge topology instead of the half-bridge that the older models used. Moreover, only the SP Platinum 550W model is equipped with a single EPS connector, with all the rest featuring two of those connectors. In the SP Gold line, the 450W, 550W, and 650W models come with a single EPS connector.

The Straight Power 11 Platinum with 550W max power is the smallest member of the line. It features a fully modular cable design along with a high-quality Silent Wings 3 fan, which uses a fluid dynamic bearing for lower noise output and increased lifetime. According to be quiet!, the funnel-shaped fan inlet increases the airflow, boosting the cooling performance. Moreover, all the internal components are of high quality, including Japanese capacitors that belong to good lines and not mainstream ones. 


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Manufacturer (OEM)


Max. DC Output



80 PLUS Platinum, *ETA-A (88-91%)


*LAMBDA-A++ (<15 dB[A])


✓ (Fully)

Intel C6/C7 Power State Support

Operating Temperature (Continuous Full Load)

0 - 40°C

Over Voltage Protection

Under Voltage Protection

Over Power Protection

Over Current (+12V) Protection

Over Temperature Protection

Short Circuit Protection

Surge Protection

Inrush Current Protection

Fan Failure Protection

No Load Operation


135mm Fluid Dynamic Bearing Fan (BQSIW3-13525-MF)

Semi-Passive Operation

Dimensions (W x H x D)

150 x 85 x 160mm


1.66 kg (3.66 lb)

Form Factor

ATX12V v2.4, EPS 2.92


5 Years

* Not certified yet by Cybenetics. According to our measurements, which are in line with the Cybenetics respective guidelines, the PSU falls into these efficiency and noise categories.

Power Specifications

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Rail 3.3V5V12V112V212V312V45VSB-12V
Max. PowerAmps22221818202030.3
Row 2 - Cell 0 Watts110    549.6153.6
Total Max. Power (W) 550      Row 3 - Cell 9

Power Distribution

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12V1ATX, Peripheral

Cables and Connectors

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DescriptionCable CountConnector Count (Total)GaugeIn Cable Capacitors
ATX connector 20+4 pin (600mm)1116-22AWGNo
4+4 pin EPS12V (700mm)1116AWGNo
6+2 pin PCIe (600mm) 2218AWGNo
SATA (550mm+150mm+150mm+150mm)1418AWGNo
SATA (550mm+150mm+150mm) / 4-pin Molex (+150mm)13 / 118AWGNo
SATA (550mm+150mm) / 4-pin Molex (+150mm+150mm)12 / 218AWGNo
FDD Adapter (150mm)1122AWGNo
AC Power Cord (1360mm) - C13 coupler1118AWG-

There is no need for two EPS connectors in such a low-capacity power supply. The amount of PCIe is sufficient and the same goes for the peripheral connectors. 

It is weird to see 16AWG gauges in a 550W PSU, but we won't complain, of course, since they allow for lower voltage drops. It is just that the production cost slightly increases, with those cables. Finally, all cables are quite long and the distance between the peripheral connectors is adequate. 

Component Analysis

We strongly encourage you to have a look at our PSUs 101 article, which provides valuable information about PSUs and their operation, allowing you to better understand the components we're about to discuss.

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Header Cell - Column 0 General Data
Manufacturer (OEM)FSP
PCB TypeDouble Sided
Row 2 - Cell 0 Primary Side
Transient Filter5x Y caps, 2x X caps, 2x CM chokes, 1x MOV
Inrush ProtectionNTC Thermistor (SCK-018)
Bridge Rectifier(s)1x
APFC MOSFETs2x ROHM R6020KNX (600V, 20A, 0.196Ohm)
APFC Boost Diode1x Infineon IDH04G65C6 (650V, 4A @ 150°C)
Hold-up Cap(s)1x Rubycon (450V, 220uF, 3,000h @ 105°C, MXK) & 1x Rubycon (450V, 180uF, 5,000h @ 105°C, VXH)
Main Switchers4x STMicroelectronics STF18N60M2 (650V, 8A @ 100°C, 0.28Ohm)
IC Driver

2x Silicon Labs Si8233BD

APFC ControllerChampion CM6500UNX
Resonant ControllerChampion CM6901X
TopologyPrimary side: Full-Bridge & LLC converter
Secondary side: Synchronous Rectification & DC-DC converters
Row 14 - Cell 0 Secondary Side
+12V MOSFETs4x Infineon BSC014N04LS (40V, 100A @ 100°C, 1.4mOhm)
5V & 3.3VDC-DC Converters: 8x Advanced Power AP3R303GMT (30V, 25A @ 70°C, 3.3mOhm)
PWM Controllers: 2x ANPEC APW7164
Filtering CapacitorsElectrolytic: 4x Nippon Chemi-Con (4-10,000h @ 105°C, KY), 2x Nippon Chemi-Con (5-6,000h @ 105°C, KZH), 4x Rubycon (3-6,000h @ 105°C, YXG), 1x Rubycon (6-10,000h @ 105°C, ZLH)
Polymer: 4x FPCAP, 18x United Chemi-Con
Supervisor ICWeltrend WT7527 (OCP, OVP, UVP, SCP, PG)
Fan Modelbe quite! BQ SIW3-13525-MF (135mm, 12V, 0.4A, Fluid Dynamic Bearing Fan)
Row 20 - Cell 0 5VSB Circuit
Rectifier1x Silan Microelectronics SVF3N80F FET (800V, 1.9A @ 100°C, 4.8Ohm)
Standby PWM ControllerLeadtrend LD7750R

This is FSP's new platform, which we will soon see in the Hydro PTM Pro line. It uses a full-bridge topology on the primary side, along with an LLC resonant converter for increased efficiency. The secondary side includes the usual: a synchronous design for the +12V rail and voltage regulation modules for the minor rails. The parts that FSP used are of high quality, especially the bulk caps, and the design is clean, without any cables obstructing the airflow. The increased clearance between the parts also enhances the airflow. Only the DC-DC converters are installed side by side, but those parts are not highly stressed in real-life conditions, and they use several FETs, which share the load.

The transient filter is complete and does a pretty good job, according to our test results. 

(Image credit: Tom's Hardware)

Since the PSU's capacity is low, there is no need for a pair of bridge rectifiers. Nonetheless, two bridges could increase efficiency, especially under high loads.

The APFC converter uses two ROHM FETs and an Infineon boost diode. The bulk caps are provided by Rubycon and are of extra-high quality. This is the first time we see a 5000h bulk cap on a desktop PSU. Usually, even high-end platforms use 2000h bulk caps. Finally, the APFC controller is a Champion CM6500UNX IC. 

The four STMicroelectronics FETs are installed on a full-bridge topology. An LLC resonant converter is also used to restrict switching losses. The primary FETs are controlled through a pair of Si8233BD drivers

All four FETs that regulate the +12V rail, are installed on the solder-side of the PCB. The DC-DC converters that generate the minor rails are hosted on two vertical daughter-boards, which are installed side-by-side. 

There are not many electrolytic caps, since FSP used a large number of polymer ones. Still, the few electrolytic caps are of high quality.

The 5VSB circuit uses a SVF3N80F FET on its primary side, and the standby PWM controller is provided by Leadtrend.

Weltrend WT7527 Supervisor IC (Image credit: Tom's Hardware)

The supervisor IC is a Weltrend WT7527 which supports, out of the box, all necessary protection features, but OTP (Over Temperature Protection). 

The face of the modular board hosts several polymer caps. 

The soldering quality is average, since in some areas the soldering joints look sloppy. Nevertheless, this won't affect performance.  

The cooling fan uses a fluid dynamic bearing and it is driven by a highly-relaxed speed profile. 

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