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Does a CPU fan add electronic noise, and how much?


CleverName

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Does having a CPU fan add electronic/EM noise in an audio/HTPC application? I am a very experienced PC builder looking to dedicate a PC I already own, but is too high powered (THD ~ 125W) to use in a fanless case.

 

If EM noise is being added by a fan in proximity to the CPU --Other options to distance the fan? What about 'silent-fan' water-cooling with the pump and radiator outside the case? Or, a ducted air-cooled solution, such as a silent fan blowing across the CPU cooler through a plastic pipe, etc.

 

So, how far would a fan need to be distanced from the CPU to eliminate EM fan noise?

 

NOTE: I am not currently interested in a low THD solution, because I need the horsepower for HD video streaming. (yep) I know that I can buy a Haswell i7 that can handle this job, but I don't want to go that route because it means an entirely new system.

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If you're serious enough to be worrying about this, you are serious enough to dedicate another machine completely to music playback. Doesnt have to be an expensive machine, but I just cant see how you can talk HD video and contemplate messing with your CPU fan - for the effort you would need to put into this I really think you are better off looking at an Atom-based CAPS machine or similar.

Just one more headphone and I know I can kick this nasty little habit !

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Oh yes.

Fan is pumping power from mother board.

Sonic improvement is close to the improvement of a good power supply.

CloneAudio LPSU for QnapHS-251 fanless - UpTone JS2 for MacMini i7 (SD card only-CAD scripts-MMK fan kit-no disc inside- Audirvana2)- JS2 for REGEN - BelCantoRefLink-TotalDacD1tube(Mullard ECC82 NOS) //Halgorythme single end 300b EML //DiY Open Baffle & Leedh Elfe

Whee was the last time you did something for the first time?

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I installed an extremely quiet Noctura fan for my quad core i5 and I was really surprised by the effect the fan running had on the sound quality. The em disturbance to the 5 volt power on the MoBo fed it's way to the E20 DAC which has a pretty good USB isolation.

 

so my suggestion is to install a big cooler, and install a quiet fan with an on off switch. A good idea would be to have a PC case with side vents and a top vent of that you can get some fanless convection air cooling taking place

 

Picture 1 of 1 from Music PC

Sound Test, Monaco

Consultant to Sound Galleries Monaco, and Taiko Audio Holland

e-mail [email protected]

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On other threads I have shown pictures of EMI readings of fan impact using the standard Mac mini one.

 

But here is another anecdote illustrating the potential impact of fans. I had a small mobile fan about 30cm in diameter with a wall wart turned on and sitting on the third floor of a building, and suddenly the garage gate would no longer open 3 floors down!

 

Putting an aluminium plate (cookie sheet) over the garage opener antenna blocked enough of the EMI to allow it to function again.

 

Cheers

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Does having a CPU fan add electronic/EM noise in an audio/HTPC application? I am a very experienced PC builder looking to dedicate a PC I already own, but is too high powered (THD ~ 125W) to use in a fanless case.

You could try a cheap SOtM Fan filter in line with the CPU fan. It's the approx. 25kHz Pulse Width Modulation fan speed control pulses from the motherboard that cause the problem. Alex C and John Swenson use a more sophisticated PWM to Linear fan filter with their JS2 Linear PSU for the Mac Mini.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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You could water cool. There are (or were) passive radiators that sit outside th PC.

Dahlquist DQ-10 Speakers DQ-LP1 crossover 2 DW-1 Subs

Dynaco Mk III Mains - Rotel 991 Subs

Wyred W4S Pre Gustard X10 DAC

SOtM dx-USB-HD reclocked SOtMmBPS-d2s

Intel Thin-mini ITX

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If you're serious enough to be worrying about this, you are serious enough to dedicate another machine completely to music playback. Doesnt have to be an expensive machine, but I just cant see how you can talk HD video and contemplate messing with your CPU fan - for the effort you would need to put into this I really think you are better off looking at an Atom-based CAPS machine or similar.

 

You are of course, correct. :) I'm just a hobbyist trying to make the best out of what is on-hand, with minimal up costs. Also don't want to have two PC's in my stereo rack below the TV.

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You could try a cheap SOtM Fan filter in line with the CPU fan. It's the approx. 25kHz Pulse Width Modulation fan speed control pulses from the motherboard that cause the problem. Alex C and John Swenson use a more sophisticated PWM to Linear fan filter with their JS2 Linear PSU for the Mac Mini.

 

Interesting product, SOtM Fan Noise Filter, good call. I am not an engineer, but I also wonder that the fan itself might generate noise, given the proximity of the fan motor to the CPU. As for the water cooling mentioned by Harpy, I have been searching around online for a passive water cooler, but no success so far. The best I am finding are radiators with fans, which I am contemplating obtaining and mounting outside the case.

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Interesting product, SOtM Fan Noise Filter, good call. I am not an engineer, but I also wonder that the fan itself might generate noise, given the proximity of the fan motor to the CPU.

 

Superdad (Alex C) found that running the fan via the John Swenson designed fan filter was almost as good sounding as running with the fan briefly disconnected. The fan could also be connected to the +12V supply using a series thermistor taped to the processor's heatsink.

A thermistor is supplied with some aftermarket low noise fans. When using PWM control, the fan motor acts as a big antenna for the 25kHz pulsed supply, and especially it's harmonics which cause the damage to SQ.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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I did a bunch of EM measurements of the Mac Mini fan when we were designing the controller. With the PWM control the EM level was almost the same no matter what the fan speed. Fed variable DC the EM was much lower at slow speeds and went up as speed increased, at full speed it was about the same as with PWM control.

 

Note this is for a Mac Mini fan, NOT a fan inside a PC, I have not measured any of those.

 

John S.

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I did a bunch of EM measurements of the Mac Mini fan when we were designing the controller. With the PWM control the EM level was almost the same no matter what the fan speed. Fed variable DC the EM was much lower at slow speeds and went up as speed increased, at full speed it was about the same as with PWM control.

 

Note this is for a Mac Mini fan, NOT a fan inside a PC, I have not measured any of those.

 

John S.

 

Hi John

Unless doing processor intensive tasks such as video editing and conversions, the fan should never be running anywhere near full speed unless it's a stinking hot day without air conditioning running.

On the fly conversion from RB CD to DSD may be a different matter though ?

 

Kind Regards

Alex

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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I have shown pictures of EMI readings of fan impact using the standard Mac mini one.10ce10.jpg

 

Are you a parrot by any chance, or just a plain galah?

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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I can hear the difference with and without the fan. But it's not dramatic by any means.

This is only done one linear psu or batteries . If using a SW psu I cannot hear any change.

I too also tried supplying the fan from external power that made no difference as the moment I turned on the fan the change was there . I have two no fan cup,s one is a caps case and the other is a water cooled unit. Both work fine but the cooler is just big and ugly for me. A small form factor caps type case is better for me.

Al

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Al

When I was running 2 front 80mm fans in my previous PC, I had them connected in series, which meant they were much quieter physically, but at the lower speed they caused much less degradation than a single fan running at a higher speed . When ripping my favourite high quality CDs , I used a toggle switch mounted on the front panel to turn them off for the duration, and a red LED to remind me to turn them back on again.

 

Alex

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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My personal experience has been that the sound degradation from fan induced electrical noise was disturbingly noticeable on a midfi system (Cambridge Audio 650A) with a high existing noise floor, but almost imperceptible on a system with low noise power amps (Hypex NC400).

 

It seems that it's the cumulative noise level that's important. If you have a dead quiet system, you can accept and not notice electrical fan noise

 

Have the fan on a switch, then you can turn it off for serious listening :-)

Sound Test, Monaco

Consultant to Sound Galleries Monaco, and Taiko Audio Holland

e-mail [email protected]

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Yea now this makes sense. As I do hear it. I have three caps all SER 2012 and AO 1.30

also a iMac I7 and a gamer cpu I7 withany fans. As the SER caps win big it's not just fans that make things better or worse

if i shutdown all fans in the gamer setup it only improves slightly

al

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It seems that it's the cumulative noise level that's important. If you have a dead quiet system, you can accept and not notice electrical fan noise

Perhaps so, but if you remove the RF/EMI from the fans, it's like lifting a fine veil from low level detail and improves the harmonic structure.

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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The information at the attached link may be of interest.

 

http://www.powerampdesign.net/images/an-24_eliminating_circuit_noise_from_cooling_fans.pdf

 

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

PROFILE UPDATED 13-11-2020

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