Inside be quiet!

The problem with passive power supply units

There’s absolutely no reason for having to endure a loud power supply unit anymore, as was quite the standard about 15 years ago. Our approach to PSUs is to equip them with high-grade components and put a very silent fan on top. But there are two developments in that field that cropped up in the last few years and warrant a closer look: passive and semi-passive power supply units.

“passive” means that the PSU comes completely without a fan, the heat dissipation is completely being taken care of by a big heat sink – which means that the system is pretty much noiseless. Sounds super, but has one major drawback: This only works up to a certain performance limit as crossing that threshold bears the very real risk of overheating the system. This means that from this point on you simply need something actively dissipating the heat thus preventing overheating and shutdown.

This brings “semi-passive power supplies” into view. By and large they are built like regular active PSUs but with the major difference that their fan is usually dormant and only springs into action when the system crosses a pre-defined performance limit, usually something between 40% and 50%, or a certain temperature threshold.


Both of these technologies claim to be extremely silent as no mechanical noises occur when the fan doesn’t rotate. While this is true they are not completely soundless – there’s always noise caused by electrical parts which is very difficult to suppress and can actually be even louder than a rotating fan. One example is the whine of the spools within the PSU which can result from high performance load or load changes.

If you happen to be familiar with our portfolio you’ll know that we don’t have passive or semi-passive power supply units on offer. All of our systems are actively cooled, with a constantly rotating fan - for a very good reason. Of course we’ve spent a big amount of time researching both developments, but in the end we’ve come to the conclusion that their specific drawbacks outweigh the benefits. Our actively cooled PSUs like the Dark Power or Straight Power series are practically inaudible while still producing a gentle airflow which hauls away the heat from the voltage transformers and capacitors. Putting a passive PSU under high pressure has a measurably detrimental effect on the life expectancy of its components. Also in these days, with PC builders equipping their systems with PSU shrouds and chamber systems there’s a higher risks of local heat accumulation – something that can cause damage to your components in the long run. You can actively work against that by ever increasing the heat sink for example, but this makes the PSU more expensive and clunky, and it does not make the problem go away. Which is why we’ve decided to stick with active cooling: We continue to develop our fans to make them even more efficient and quiet – so that your system is always reliably cooled and whisper-quiet at the same time.