How does this work?

Chris Beard

Chris Beard

Chris Beard

Associate
Joined
17 Apr 2006
Posts
2,240
Location
Hampshire
I'm interested in reducing the intensity of the 'jerk' of the pwm pulse that propels my fans in an attempt to reduce the volume of the pwm 'click'.

Does anyone know what the anatomy of these are please?:

Noctua NA-SRC7 4-Pin PWM Low-Noise Adaptors, 3 pack

Are they just a resistor, a series of diodes, a switching voltage regulator, something else? If someone has one - do they get warm to the touch?
 
It's generally just a resistor. Of course the exact voltage dropped depends on the current so varies from fan to fan and on speed.

But yes these are usually just a resistor. Although if that's the case, I don't know what happens with PWM fans, because these usually have a fixed voltage and pulse it. So between pulses, with theoretically no current, the voltage will increase back up to 12V.

That said, we're overthinking this - it won't kill anything so give it a try!
 
LuckyBenski said:
Although if that's the case, I don't know what happens with PWM fans, because these usually have a fixed voltage and pulse it. So between pulses, with theoretically no current, the voltage will increase back up to 12V.
Click to expand...

Interesting; this may be exactly what I want, to 'soften' the pulse, as with increased current draw to power the fan it will deaden the movement. I never considered the non-instantaneous current increase.

LuckyBenski said:
That said, we're overthinking this - it won't kill anything so give it a try!
Click to expand...

This is probably also true :-)
 
Quote from the advert 'The NA-SRC7 contains three resistors for reducing the speed of 4-pin PWM fans by around 30%.' I would imagine that's one resistor per cable, I have one of those and it feels like a resistor under the the outer covering. Athough mine is a NA-RC7
 
Hmmm, just a quick question. Are you sure you've got pwm fan headers and not just voltage control with 4 pin pwm header? As this could be a different issue then thats causing the fan to click as its voltage reached stall levels on the fan through reduced voltage instead of pwm being altered. In this situation, adding a resistor cable will only alter the value where the fan stalls and cause the clicking.

I encountered this issue using the "supposedly" pwm fan headers on my Asus Rampage IV Extreme. But it turns out its not real pwm. Only the cpu headers were real ones. The rest were voltage control hidden as pwm. Got the Aqua Quadro then Octo pwm fan controllers and can now send the fans down via pwm to extremely low levels and they won't click.

So just a note to look at on your end just in case you fall into the same situation.
 
Meddling-Monk said:
Hmmm, just a quick question. Are you sure you've got pwm fan headers and not just voltage control with 4 pin pwm header?
Click to expand...

Thanks for the heads up!

I'm running a pwm hub, so voltage control wouldn't alter the fan speed. There is a very considerable difference in volume between the different PWM settings for the fans, so I'm very confident the PWM signal from the mobo is working.

I'm also using an ASUS board, and whilst I am using the CPU header, I think all the headers support both PWM and Voltage control. There's a setting somewhere that I had to change for a fan from another header - seemed to work for me.

Your board is a lot lot nicer than mine. I'm surprised your board doesn't also have this setting and only offers voltage control. Especially as voltage control is more expensive to implement for the board maker!
 
Silicon Si said:
Quote from the advert 'The NA-SRC7 contains three resistors for reducing the speed of 4-pin PWM fans by around 30%.' I would imagine that's one resistor per cable, I have one of those and it feels like a resistor under the the outer covering. Athough mine is a NA-RC7
Click to expand...
It's not per cable, but just for voltage.

And might be actually some sorts of diodes to get controlled voltage drop.
(forward voltage of ordinary diode or maybe reverse biased zeners)
Because of current varies between fans, using resistors would cause different voltage drop with different fans.
 
Chris Beard said:
Thanks for the heads up!

I'm running a pwm hub, so voltage control wouldn't alter the fan speed. There is a very considerable difference in volume between the different PWM settings for the fans, so I'm very confident the PWM signal from the mobo is working.
Click to expand...

That's OK, so long as the point raised is covered, then we know you're not wasting time/money on something that won't work. That's the key thing. :)

Chris Beard said:
I'm also using an ASUS board, and whilst I am using the CPU header, I think all the headers support both PWM and Voltage control. There's a setting somewhere that I had to change for a fan from another header - seemed to work for me.

Your board is a lot lot nicer than mine. I'm surprised your board doesn't also have this setting and only offers voltage control. Especially as voltage control is more expensive to implement for the board maker!
Click to expand...

Yeah, from all the latest reports on the x79 boards, it appears Asus cheapened out on the Rampage IV Extreme in the PWM, and the sensors and cooling department, using somewhat more questionable choices compared it its contemporaries by Asus. Some of the less pushed X79 boards by them were better supported and had more appropriate (passive) cooling and sensor suite in comparison. There's no VRM temp monitoring capability for example, so you need to stick your own temp probe on the VRM to get a rough idea where it's at.

Anyway, side tracking a bit there, let us know how the cables works for you. :)
 
You must log in or register to reply here.
Back
Top Bottom