MSI MAG A550BN Power Supply Review

MSI has built a reputation for offering high-quality products catering to gamers and enthusiasts. Known primarily for its motherboards and graphics cards, MSI also expanded its presence in the PSU market, aiming to deliver reliable, performance-driven solutions for all types of PC builds.

This review focuses on the MSI MAG A550BN, a 550W PSU designed for budget-conscious builders. With an 80Plus Bronze certification and a $50 retail price, this unit targets users seeking dependable performance without breaking the bank. While lacking some premium features, such as a 12+4 pin PCIe connector for the latest GPUs, the MAG A550BN positions itself as a competitive choice in the entry-level market.

Specifications and Design

In the Box

The MSI MAG A550BN comes packaged in a sturdy cardboard box featuring a simplistic dark-themed design. The PSU itself is protected by a nylon pouch and foam inserts, ensuring safety during transit.

MSI includes only the essentials in the box, such as mounting screws and an AC power cable. While the bundle is minimal, it is sufficient for straightforward installation and we do not normally expect anything more from a product of this price range.

The PSU’s all-black cables are flat and ribbon-like. The 24-pin ATX cable is the only one that features black nylon sleeving. The unit provides two 6+2 pin PCIe connectors. There is no 12+4 pin PCIe connector for newer graphics cards, limiting its compatibility with high-end GPUs; an adapter may be used, but the low power output of the unit could spell trouble lest the system builder is highly experienced.

External Appearance

MSI spent a lot of resources in an effort to make the unit aesthetically appealing. The MAG A550BN features a sleek and modern design, with a satin black finish on the chassis that is somewhat prone to fingerprint smudges. The PSU adheres to the ATX standard length of 140 mm, ensuring compatibility with most ATX-compliant cases, even compact ones.

The hexagonal fan grille is integrated into the chassis and presents a clean, symmetrical design, adding a subtle touch of style to the unit. Both sides of the PSU are decorated with an embossed pattern and the series logo etched into the paint, adding a layer of sophistication without being overly flashy.

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Positioned at the rear are the AC receptacle, power switch, and a button for enabling or disabling the hybrid fan mode, which allows the fan to remain off at low loads, minimizing noise. The modular cable connectors are located at the front, with a subtle legend printed nearby for ease of identification.

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Internal Design

The MSI MAG A550BN is cooled by a 120 mm Hong Hua HA1225H12S-Z fan with a fluid dynamic bearing (FDB) engine. This type of bearing ensures excellent acoustics and a longer lifespan compared to sleeve bearings. Finding such a high-quality fan in a sub-$50 unit was a pleasant surprise.

The OEM responsible for the MAG A550BN is Channel Well Technologies (CWT), a respected manufacturer known for creating reliable platforms. Interestingly, this PSU is built on a newly designed platform specifically tailored for the budget segment, rather than an older one with minor tweaks.

The filtering stage is well-equipped, featuring four Y capacitors, two X capacitors, and two filtering inductors. A single rectifying bridge mounted on a basic heatsink is followed by the Active Power Factor Correction (APFC) stage, with two MOSFETs and a diode on a large heatsink. The passive components include a single Jun Fu 270 μF capacitor rated up to 85°C and an encased inductor. On the primary side, two IPS ITA20N50R MOSFETs handle the inversion process and are mounted on the same heatsink as the APFC components.

On the secondary side, four MOSFETs generate the 12V rail, while DC-to-DC converters on a vertical daughterboard handle the 3.3V and 5V rails. The capacitors used in the secondary stage are a mix of ChengX and CapXon products. The CapXon capacitors are considered of mediocre quality, while ChengX and Jun Fu products are unusual finds in a quality PSU. MSI backs this unit with a 5-year warranty, partially alleviating quality concerns.

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Cold Test Results

Cold Test Results (25°C Ambient)

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M 40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts.

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During cold testing, the MSI MAG A550BN comfortably meets its 80Plus Bronze certification requirements across various input voltages. At 115 VAC, it achieves an average nominal load efficiency of 86.1%, which improves slightly to 88.1% under a 230 VAC input. Efficiency peaks at around 40–50% load, a typical characteristic for PSUs in this class. The MAG A550BN maintains passable performance throughout the nominal load range (10-100%), with acceptable efficiency at very low loads.

The Hong Hua HA1225H12S-Z fan maintains a very low speed until the load exceeds 300 watts, maintaining low noise figures up to approximately 400 watts. Beyond this threshold, the fan speed increases linearly, becoming clearly noticeable at higher loads but never reaching its maximum speed, even at full load. Internal temperatures are well-regulated during cold testing, keeping components within safe operational limits.

Hot Test Results

Hot Test Results (~45°C Ambient)

During hot testing, the MSI MAG A550BN shows a noticeable decrease in efficiency under elevated temperatures, particularly at higher loads. The efficiency averages 84.5% at 115 VAC and 86.5% at 230 VAC, compared to 86.1% and 88.1% observed during cold testing. This decline of approximately 1.6% is expected considering the class of this unit but remains within acceptable performance levels with minimal signs of thermal stress at maximum load.

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In warmer environments, the fan in the MAG A550BN speeds up more aggressively than during cold testing, starting to ramp up its speed when the load exceeds 200 watts. The fan speed increases steadily with the load, reaching maximum speed when the load approaches 90% of the unit's rated capacity. Under sustained heavy loads, the fan becomes quite audible as it works to manage internal temperatures. While the unit's thermal performance is adequate, internal temperatures approach the upper limits of the passive components' specifications, suggesting a potential struggle to maintain optimal operating conditions during extended periods of heavy use.

PSU Quality and Bottom Line

Power Supply Quality

The MSI MAG A550BN demonstrates solid performance within its class, offering reliable electrical stability and power quality. Voltage regulation is satisfactory, with the 12V rail holding at 1.0% and the 3.3V/5V rails at 0.6% each. Ripple suppression is respectable for a budget-oriented PSU, with maximum ripple levels measuring 48 mV on the 12V rail, 14 mV on the 5V rail, and 16 mV on the 3.3V rail. None of these figures is setting any records but the A550BN demonstrated excellent performance overall for such a low-cost unit.

During our thorough assessment, we evaluate the essential protection features of every power supply unit we review, including Over Current Protection (OCP), Over Voltage Protection (OVP), Over Power Protection (OPP), and Short Circuit Protection (SCP). All protection mechanisms were activated and functioned correctly during testing.

The MAG A550BN’s OCP is calibrated to activate at 135% for the 3.3V rail, 140% for the 5V rail, and 114% for the 12V rail, with an OPP setting at 118%. These values are good and safe for a low-cost design that does not require ATX 3.0/3.1 compliance. On the other hand, the sharp OCP can become an issue should some user decide to use an adapter to power a modern high-performance graphics card.

Bottom Line

The MSI MAG A550BN is a budget-friendly and functional power supply unit that strikes a solid balance between performance, reliability, and cost, making it a viable option for users on a strict budget or those building entry-level systems. Conforming to the ATX 2.4 standard, the MAG A550BN includes the necessary connectors for efficient builds. Its compact design and non-modular layout, while less flexible than modular alternatives, make it a practical choice for users who value simplicity and cost-efficiency. The illogicality with the MAG A550BN lies in the fact that MSI directed a lot of its resources on the aesthetic improvement of a non-modular unit, where slightly better components would make more sense.

Internally, the MAG A550BN is built with cost-effective components, including basic capacitors from brands like Jun Fu and ChengX, which are far from the first choice of anyone designing a high-quality PSU. These components are sufficient for typical systems but may limit the PSU’s longevity in more demanding setups or heavy workloads. In contrast, the unit uses a top-quality 120 mm FDB fan. The fan is very quiet when the load is relatively low, but under higher loads and/or if the ambient temperature gets high, the fan becomes audible as it ramps up to keep the unit cool. The fan's noise level is acceptable but could be a consideration for users aiming for ultra-quiet builds.

In terms of electrical performance, the MAG A550BN demonstrates solid voltage regulation and ripple suppression that is within industry limits, ensuring stable power delivery for most components. Efficiency is respectable, meeting 80Plus Bronze standards, which is adequate for its price point, though it clearly falls behind higher-tier models in terms of overall energy efficiency and quiet operation, especially at higher loads.

At a retail price of around $50 and a 5-year warranty, the MAG A550BN presents an attractive option for budget-conscious users, though it faces stiff competition from other PSUs that offer slightly better components at a comparable price, or significantly better performance for just a few dollars more. While the MAG A550BN offers a solid and reliable solution for entry-level builds, it may not be the best choice for users who prioritize high-quality components or need higher efficiency and cooling performance under load. Despite these areas for improvement, the MAG A550BN remains a practical, affordable option for mainstream PC builders and enthusiasts looking to maximize value without breaking the bank.

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