Originally Posted by doyll
Correct, if no PWM signal is present the fan functions as a normal 12 volt fan. But that does not mean PWM fans cannot be used with variable voltage control
Noctua website in NF-A15 PWM, NF-A14 PWM, fan says
It says same for F-A20, NF-A12x15, NF-A12 .. and I stopped looking.
My understanding of the English language interprets that to mean Noctua is saying it is fine to use LNA with PWM control. Which contradicts what you said.
So please supply some links to credible sources supporting your claims or stop making them.
In my experience trying a voltage reducing adapter with cougar fans, it effected the whole range of rpm and produced a very small window of operation and the pulses were audible when between 40 and 100% operation.
Noctua may specifically design their fans for use at lower voltages, but other fans may have ill effects when lowering voltage and using pwm.
I would recommend either using pwm or voltage control, not both. In software you can set the maximum pwm rate, and the curve will be unaffected. There might be some special cases that need to use a voltage adapter, such as higher speed fans on an aio that does not have adjustable software, but those are outliers for the most part.
I never said that it would be damaging to the fan, but just that it is not recommended. If you need to use a voltage adapter on a pwm fan, you bought the wrong fan.
Designated PWM fans not only have internal circuitry which differs from that of standard fans, but because they are designed with speed control in mind the motors themselves are usually more advanced (and expensive). So, PWM speed control of a standard fan is indeed very different from PWM speed control of a PWM fan… Nidec even goes so far as to say that modulating the main supply voltage is not advisable
Quoted from the article listed above. The quote gilles posted is referring to supply voltage to pwm fans, and that it should not be modulated (by pwm voltage control, but true voltage control should not cause damage, just lower the speeds across the range since you replace 12v with 7v or 9v).Edited by EMUracing - 9/20/17 at 1:38am