A higher wattage version of the SX500-LG? Dual Titan-Xs here I come
http://www.techpowerup.com/212925/silverstone-ready-with-a-700-watt-sfx-l-power-supply.html
In addition to higher capacity, Silverstone has implemented a new type of fan control. Instead of being adjusted by temperature follows the fan load rating, something that to do that it remains switched off even at low loads.
http://www.sweclockers.com/nyhet/20641-silverstone-tar-formfaktorn-sfx-l-till-700-w Google Translated
The new fan controller is load-based, meaning it'll start, stop, and adjust the speed based on the power load. However, it has a backup over-temp sensor that will kick the fan on regardless of load if the temperature gets too high.
Like I said though, the clacking is present even at higher RPMs, well above the threshold point. Phuncz may just have gotten lucky and his particular fan doesn't make the noise.The only other explanation is there was something wrong with the semi-fanless feature in the SX500-LG and after that thermal threshold was reached, it was consistently trying to turn itself on/off and causing that noise.
Or Antec, Scythe or any of the other brands using the OEM design. I can only hear some whirring with my ears about 10-15cm from the fan when idle. But add the slightest white noise and it's inaudible. It might be some people having units with not so decent fan bearings.True enough, I suppose we'd need more user accounts of those with Sharkoons to get a better idea.