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Almost all case fans run on the 12V DC supplied through a power supply. One way to reduce fan noise is to supply a lower voltage to the fan. All ATX power supplies provide both 12V and 5V DC outputs. A case fan could run on a 5V voltage, but the 58.3% voltage reduction would significantly reduce the cooling power of the case fan. An alternative is to use the 12V as the positive and the 5V as the negative (ground), using the voltage difference as 7V. With 7V, the voltage is dropped only 41.7% from 12V, but it is 20% higher than 5V allowing enough cooling while effectively reducing fan noise.

First off we have the regular male molex end connector. This pin number and color relationship are the same whether it's a male or female connector. The connectors are designed (keyed) so they only fit together one way, which prevents you from damaging your hardware.


Next we have the fan connector. Note the red wire is 12V+ and black is ground.


To run your fans at 7V (12V-5V) simply run the red fan wire to the 12V pin of the molex connector and the black to the 5V pin as shown below.


Enjoy your quiet fans!

Images from bleedingedge.com

Feedback received on this FAQ entry:
  • Can you offer advice how you swap the wires over ? please. I am using a Stardon ST2 firewire drive which has a three pin connector to the fan. Regards Rob

    2014-01-12 18:42:36



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by Exit See Profile edited by FastEddie See Profile
last modified: 2004-05-24 18:49:10