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be quiet! System Power U9 700W PSU Review

Today we have reviewed the be quiet! SU9-700. It is worth emphasising again that this is the System Power U9 700W – a unit only available in the US and Taiwan as it is aimed at the 110V market. UK and European buyers (230V) will be able to buy the System Power 9 700W – no ‘U' in the name – though the two power supplies are based on different platforms, so they are not identical units just with different names.

Still, the be quiet! SU9-700 might be a budget oriented unit but the performance is quite good and in terms of load regulation it managed to impress us. The non-modular cables provide it with a head start of course, since they have lower voltage drops compared to modular ones … especially at high loads.

The cherry on the cake is the ultra quiet operation, something that it is really difficult to find at this price and efficiency range. The lower the efficiency the higher the energy losses so the cooling system has more work to do, and in the majority of cases this means increased airflow – so noise emissions can get higher.

I believe that the price of this product is fair, given its features and the registered performance, however I would like to see a better cap in the APFC converter. A similar capacity Nippon Chemi-Con bulk cap with an 105°C rating wouldn't notably raise the cost (less than £1 difference) but it would offer a much longer lifetime.

On the other hand, the caps in the secondary side are of acceptable quality since Elite caps are the best that money can buy today from the Chinese market. Using Chemi-Con or Rubycon would greatly affect the cost and the Elite VE caps have a pretty long lifetime — technically longer than the lifetime of the popular NCC KZE caps used in many high-end power supplies today.

The non-modular cable design might be a deal breaker for many of you, since today the majority of power supplies are equipped with fully modular cables. Nevertheless, in a budget unit the first thing that usually has to go are the modular cables – which is acceptable if the performance is high enough. Thankfully this unit is a solid all round performer.

The list of changes that I would like to see in the next revision of this platform are as follows:

  • Higher capacity and 105°C temperature rating bulk cap (preferably a Japanese model).
  • Improve the transient response, especially at 3.3V.
  • Equip the unit with a rifle bearing fan which will last for much longer.
  • Install a bypass relay for the NTC thermistor, to enhance the inrush current protection.

US customers can buy the the be quiet! System Power U9 700W from Newegg for $74.90 HERE.


  • Fair price given what it offers.
  • Delivered full power at over 40°C.
  • Easily meets the 80 PLUS Bronze and ETA-A- efficiency requirements.
  • Silent operation (LAMBDA-A).
  • Tight load regulation.
  • Accurate power ok signal (but lower than 16ms).
  • Efficient 5VSB rail.
  • Compact dimensions.


  • 85°C bulk cap (and of low capacity).
  • Sleeve bearing fan.
  • Low hold-up time.
  • The non-modular cable design can be a deal breaker for some.
  • Not so good transient response (especially at 3.3V).

KitGuru says: The be quiet! System Power U9 700W is a very quiet power supply that performs at a high level considering the asking price. If you don't mind the non-modular cable design and you are working with a tight budget then the SU9-700 is definitely worth considering. 

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Rating: 7.5.

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