be quiet! System Power U9 500W PSU Review: Affordable and Quiet

Specifications and Part Analysis

The System Power line by be quiet! targets users on tight budgets, who still want a reliable and silent power supply. The $54 (£36) SU9-500 ticks all the boxes since it is based on a solid CWT platform and on top of that it has low noise output, despite of the mediocre efficiency levels. This unit competes well against the highly-popular Corsair CX450 providing a good alternative to users that want to build a silent system, since the SU9-500 is notably quieter.

The be quiet System Power U9 line consists of four members with capacities ranging from 400W to 700W. These are mainstream units, suitable for cost-effective systems with low power requirements where efficiency isn't priority one. In our opinion efficiency, which in a power supply represents the ratio of the output power divided by the input power, is of immense importance. However, many users put their budget first so there is great demand for affordable, but less efficient units like the SU9-500.

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The SU9-500 doesn't have any modular cables, since those ones are usually the first to go in the effort to restrict the production cost. The platform that it is based on uses some modern touches though, which include the DC-DC converters that generate the minor rails. Usually in this price range we find group regulated power supplies, meaning that the 12V and 5V are generated by the same circuit so the performance is poor in unbalanced loads (i.e. very high loads at 12V and minimum at 5V and vice versa). This is not the case with PSUs that have DC-DC converters for the 5V and 3.3V rails, since the regulation of those rails is independent from the +12V rail.

Specifications

Power Specifications

This brand (be quiet!) is not a supporter of single +12V rail PSUs, so the SU9-500 has two of them with up to 40 Amps combined current output.

Cables & Connectors

All cables are fixed and long enough, so there won't be compatibility problems with up to mid-tower chassis. There is one EPS connector along with two PCIe ones. The number of peripheral connectors is adequate for a budget PSU, while the distance between those connectors is small. Ideally, it should be 150mm because several system components that use them (e.g. case fans), are not close to each other.

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Power Distribution

Given the restricted number of +12V rails, the power distribution is good since the EPS connector is not mixed up with the PCIe ones.

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.

This is an older CWT platform with some modifications in the secondary side, including a pair of DC-DC converters which handle the 5V and 3.3V rails. Those converters offer good performance under all conditions, even when the loads are unbalanced among the rails.

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The filtering capacitors are provided by Elite, so they are of decent quality. Actually Elite caps are considered the best choice for budget platforms, offering good reliability and performance at a good price. Some polymer caps are also used, with two of them installed on the board that hosts the DC-DC converters.

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The cooling fan uses a sleeve bearing, which will be able to outlive the provided warranty period even under not ideal conditions. We didn't expect to find of course an FDB or a double-ball bearing fan in a mainstream PSU, however it would be nice to see a rifle bearing fan used instead. Finally, a 105°C bulk cap would be a safer choice, especially in regions with 115V mains.

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