Cooler Master V Semi Modular V550S: revised and better than before!

Conclusion and evaluation

The Cooler master V Semi Modular V550S (RS-550-AMAA-G1) passed the combined and crossload testing in accordance with ATX specification so according to my evaluation methodology, it deserves its evaluation. The methodology has been changed effective from this review so read it carefully!

The worst thing about the unit is the voltage regulation of the stand-by supply which uses somewhat cheaper components designed for lower power (yet it provides nice efficiency). The voltage already starts quite low and drops even lower with load. Fortunately the regulation is not so dramatic under combined load, the −12 V rail is actually somewhat worse in this matter. It uses regulator for −12 V but with high load on that rail under lower overall combined loading, the transformer winding does not provide enough power so the voltage drops to a level the regulator cannot work correctly with.

Under such circuimstance also the ripple is high on −12 V rail as the regulator is not capable of doing anything with the fan loading characteristic. That happens in both combined load and crossload scenarios. Later with higher load, the ripple suppression was generally outstanding, with all rails then under 20 mV and the +12 V rail did not even cross 15 mV under overload. Most protections are working or the unit handles the load for so long some other protections kicks in, that is mostly the OTP as the secodnary heatsink is quite small and with high power output it overheats.

The V550S is now even quieter than before while its main competitors, Seasonic S12G/G units are noisier, this is funny situation. It still has room for improvement, mostly with size of secondary heatsink. But it is quite impressive how much power this supply can handle with such small components. Most of them are much smaller than what I am used to so the unit is quite empty yet it handles over 700 watt under overloading. One of the bigger components is high-quality high-capacity input capacitor thanks to which the unit provides hold-up time of approximately 25 ms on the +12 V rail.

Its efficiency is very high, even while crossloading the +3.3 V rail. So we have highly efficient semi-modular unit with 100% quality-components, quite silent and with highly competitive price. If only the build quality, or rather factory cleaning procedure was better as I found very high number of solder balls which are potential risk waiting to cause (catastrophic) malfunction. Now I can still only give bronze award, if this aspect was better surely it would be silver.

So the value of Cooler Master V Semi Modular V550S as high-end unit is as follows:

  • components used: 6 p. (− for thinner wires, − for lack of gold-plating, + for working OTP)
  • built quality: −16 p. (− for worse soldering, − for swarf on aluminium heatsink)
  • voltage regulation: 6 p. (− for combined loading, + for crossloading)
  • ripple: 16 p. (+ for combined loading, + for crossloading)
  • efficiency: 17 p. (+ for higher efficiency, + for high efficiency even under +5/+3.3 V crossload)
  • hold-up time: 17 p. (+ for longer hold-up time)
  • others: 7 p. (+ for modular cabling, + for longer warranty)

If we would say the price was 2200 CZK, than the price per value ratio would be 100×53/2200 = 2.41. For now this number does not tell much but with more units evaluated by this newer methodology, you can compare based on actual price. I will also add comparison table next time when we will have at least two units to compare where units will be scaled based on their value. Stay tuned!


+ high efficiency
+ high-quality capacitors
+ very good ripple suppression
+ good voltage reglation of +3.3, +5 and +12 V
+ semi-modular cabling
+ good price

bad factory cleaning (lot of solder balls)
 worse +5 V SB and −12 V voltage regulation

Be aware of…
/?\ different revisions bearing the same model name and codename!


I thank the Cooler Master company for providing the Cooler Master V Semi Modular V550S.


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