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PSU noise and Windows 7

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PSU noise and Windows 7

Postby jtcoops » Thu May 09, 2013 3:59 pm

Hello

I posted a while back regarding a new build PC which was generating noise through the desk. At the time I suspected the case, or power supply or graphics card. Anyway, I have had a lot of time to investigate this and can now categorically state it is the power supply, but only when running Windows 7.

On startup, and in the bios screen everything is silent. On the Windows 7 splash screen all is silent. As soon as the desktop hits, theres a load of high end noise, a bit like morse code, but more irritating. Control room doesn't have to have speakers up loud to hear this.

So, I replaced the PSU. Slight difference, not enough though, so went all out and put a 650w PSU in - noise much much worse.

So, to rule out a couple of things, I put the new PC side by side with the old PC (which was silent) and hooked up the PSU of the old PC to the motherboard and drives of the new PC. Noise returned, but this time I could hear exactly what I hear from the speakers coming from the old PC's PSU. Again, not until the Windows 7 desktop appears, but the old PC's PSU really started making high pitch noises in the same pulses I got from the other 2.

Therefore, what is it with Windows 7 and PSUs? I have disabled power management, have tried different power profiles, have used different GFX cards, tried different hard drives. The leaves the motherboard (MSI) memory (Kingston - pretty high end Kingston too) or Windows 7. Just to make sure I wasnt going insane I hooked up the hard drives from new PC to old PC, booted to Windows XP and everything was fine.

Has anyone experienced this, or found a solution? I am on the verge of giving up, and going back to my trusty XP - it may be slow but at least it was quiet.

Any advice much appreciated. We've been through the ground loop tests on the earlier post. I decided to post afresh as this is now targetted and I know what I'm dealing with.
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Re: PSU noise and Windows 7

Postby BJG145 » Thu May 09, 2013 7:35 pm

jtcoops wrote:I posted a while back regarding a new build PC which was generating noise through the desk...I have had a lot of time to investigate this and can now categorically state it is the power supply, but only when running Windows 7

I skipped at this point. Guess again.
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Re: PSU noise and Windows 7

Postby jtcoops » Thu May 09, 2013 10:17 pm

Not the most helpful of responses. I've done with guessing hence posting, and if you hadn't skipped you'd have found why I came to this conclusion. Until Windows 7 fully launches everything is silent. I've tried 3 different GFX cards, 2 different Firewirecards and 3 different PSUs so its either Windows 7 or the motherboard, and when in the Bios and UEFI screens again its silent so points to something Windows 7 is doing to cause significant switch activity in the PSUs that is causing the problem. The same PSU on a Windows XP install is silent, but with Win 7 as soon as it launches I can hear the same sound coming directly from the PSU

Unfortunately I don't have another motherboard to test, and frankly am more inclined to sell the whole lot now and start again with an off the shelf HP or Fujitsu than play around with buying another motherboard to rule out yet another component without something a bit more concrete pointing the finger at the possible cause.
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Re: PSU noise and Windows 7

Postby dmills » Thu May 09, 2013 10:50 pm

It is probably the interaction of the CPU power save while idle stuff and the VRM on the motherboard.

Very common problem, for all that it really indicates that you have some kind of ground loop going on, firewire can be a pain in the toot for this.

Fortunately the superficial fix is also usually easy, go into the bios and find the place where the cpu "C states" can be configured, reduce the power saving to minimum, also turn off dynamic clock switching or whatever it calls it (Both things get different names in different bios implementations).
In windows, switch the power saving off (IIRC it calls it "Performance mode" or something).

Odds are the problem will go away (And the fans will run a little bit harder).

HTH.

Regards, Dan.
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Re: PSU noise and Windows 7

Postby BJG145 » Fri May 10, 2013 7:56 am

dmills wrote:Very common problem, for all that it really indicates that you have some kind of ground loop going on

Very likely. There's a sticky thread about it here...

http://www.soundonsound.com/forum/showf ... 65&fpart=1

What audio interface are you using...? A hum eliminator might be the simplest fix.
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Re: PSU noise and Windows 7

Postby jtcoops » Fri May 10, 2013 8:07 am

I will check the BIOS this morning, although its a stupid UEFI thing and having gone through it yesterday I dont recall seeing any of the options mentioned.

I am also sure its not a ground loop as I went through all those checks before posting. Also, if I open the case and put my ear to the PSU I can hear exactly the sounds coming from it that I can hear through the speakers. PSU is silent until Windows 7 launches - if it were a ground loop the noise would be present from power on.

Quite likley to be a CPU stepping issue as that I understand draws more power from the PSU, and as soon as I click shutdown, and the blue Windows shutting down screen appears, the noise stops - presumably because the CPU goes idle.

Interface is Motu 24 i/o. As I have the old PC still available, I have ruled out all the cards and interfaces, and even when not connected to the desk in any way the noise is still there - so must be EMF interference that the desk is picking up and amplifying, and it can only be the PSU causing it. Now whether that is because of something on the motherboard, or CPU is another matter, because its only when loaded to Windows 7 the noise starts.

Losing sanity a bit now....
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Re: PSU noise and Windows 7

Postby BJG145 » Fri May 10, 2013 8:20 am

I may be wrong, but the thing about the noise starting up when the OS boots reminds me more of the audio interface kicking in than some change in power management. Maybe you could try a cheap hum eliminator as an experiment if you haven't already...? BIOS settings sound a red herring to me.
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Re: PSU noise and Windows 7

Postby jtcoops » Fri May 10, 2013 10:11 am

That would have been my original hunch, except the audio interface is fine with the other computer and the noise is audible directly from the PSU - when testing yesterday using the old computer's PSU I left it attached to the old computer - they were side by side, cables linked across, my head in the middle of both computers and the noise was coming from the old computer's PSU on the left, not from components in the powered computer on the right. However to rule out 100% I'll remove the PCI424 card from the new computer along with everything else apart from the boot HDD and see what happens.
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Re: PSU noise and Windows 7

Postby jtcoops » Fri May 10, 2013 10:12 am

I'll also have a go at recording the noise and upload it somewhere - might make this process easier as its not hum, or earth noise.
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Re: PSU noise and Windows 7

Postby Martin Walker » Sun May 12, 2013 1:17 pm

The days of ground loops only resulting in hums or constant buzzes are long gone I'm afraid

Digital ground loops (i.e. ground loops involving any digital equipment) can result in hums, buzzes, scratchy digital noises that are in sync with hard drive activity, mouse movements, graphic redraws...

I still see occasional diagnoses involving close physical contact between the audio interface and a 'noisy' component such as a graphics card, but personally I haven't experienced any such issues since the late 1990's, and Lynx Audio's superb audio interfaces do rather prove that it's possible to achieve exemplary audio quality inside the vast majority of computers.

Sadly, many musicians seem to think that small amounts of such background noises are inevitable in computer audio, but it's perfectly possible with even budget audio interfaces nowadays to completely eradicate them and end up with just a tiny amount of hiss that's only discernable when you put your ears right up against your loudspeakers.


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Re: PSU noise and Windows 7

Postby Avinash Kumar » Mon May 13, 2013 10:50 am

Please follow the below steps:

1.Make sure about the room temperature and boot the system. Click the "start" button in Windows 7 type "Power Plan." And click Choose a Plan. Select the "Power Saver" plan. Restart the computer and see if the fan is quiet enough.

2. Make sure about the error in which fan.

3. Boot off the system to minimize temperature inside the PC. Remove the cover and blow canned air into the computer to remove dust.

4. Place the computer in a cooler room, or turn on the air conditioning in the existing room.

If your Windows 7 still noise, go for windows tech support spam link removed
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Re: PSU noise and Windows 7

Postby jtcoops » Tue May 06, 2014 6:42 pm

A year on but figured I should give an answer on this as to what caused the problem

After a lot of internet trawling I found someone who had found the earthing of MSI motherboards is compromised because they dip the motherboards in some kind of lacquer. I took the motherboard out, and with a multimeter checked and all but one of the earthing points (where the motherboard gets attached to the case) was completely insulated by lacquer. Gently scraping off the lacquer and checking all the points again I reassembled and all the noises were gone.

It seems like a common problem particularly with MSI - as the board can't earth it goes through the PCI cards, and as the Motu is earthed that's why it was picking up so much "electro noise".

Hope it helps someone else stumbling on this thread.
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Re: PSU noise and Windows 7

Postby zenguitar » Tue May 06, 2014 7:50 pm

And thanks for making the effort to update the thread with your happy ending

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Re: PSU noise and Windows 7

Postby Hugh Robjohns » Wed May 07, 2014 10:16 am

jtcoops wrote:I took the motherboard out, and with a multimeter checked and all but one of the earthing points (where the motherboard gets attached to the case) was completely insulated by lacquer. Gently scraping off the lacquer and checking all the points again I reassembled and all the noises were gone.

Good find! It makes perfect sense that poor internal grounding of the motherboard could cause noise problems as you described. Thanks for reporting back and providing hopefully useful advise for others.

H
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Re: PSU noise and Windows 7

Postby Pete Kaine » Wed May 07, 2014 4:08 pm

Thanks for coming back and posting. That is also the first time I've seen this as a issue & solution, despite coming across the issue more than a few times. It might save myself and others a migraine in the future!
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Re: PSU noise and Windows 7

Postby Martin Walker » Fri May 09, 2014 6:00 pm

Pete Kaine wrote:Thanks for coming back and posting. That is also the first time I've seen this as a issue & solution, despite coming across the issue more than a few times. It might save myself and others a migraine in the future!


Indeed - I've always known this is a theoretical problem area, but I haven't ever heard of someone actually suffering from it before in practice

Thanks for posting the solution jtcoops !!


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Re: PSU noise and Windows 7

Postby Goddard » Mon May 12, 2014 6:24 am

Glad to hear the problem has been resolved. But, yikes, that's a really odd one!

The need for good earthing of the motherboard to the chassis has been mentioned here previously, and indeed the motherboard manufacturer exposed an earthing point surrounding one of the motherboard's mounting holes to that end.

That "lacquer" surrounding the other mounting holes is actually a non-conductive solder-resist mask coating applied during manufacture to avoid errant solder flow during reflow and wave soldering processes. So, very much done by design, and certainly not to compromise the board in any respect.

The exposed earthing point on the motherboard (typically surrounding a mounting hole located towards the board's center) is connected internally to the multi-layer board's buried "ground plane", so a good metal-to-metal contact there when mounting tne board to the chassis is essential for earthing the board's ground plane. But it should not normally be necessary to scrape away at the board's other mounting holes, so long as a good solid earthing contact is obtained at the manufacturer's exposed internally connected mounting point.

That said, earthing of a board's ground plane(s) is only one part of the noise-prevention design solution, and nasty noise can still crop up if proper decoupling practice is not implemented (a whole other topic, for another day).

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Re: PSU noise and Windows 7

Postby Folderol » Mon May 12, 2014 6:19 pm

Most unusual.
Filed away for future reference!
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Re: PSU noise and Windows 7

Postby Goddard » Mon May 12, 2014 8:49 pm

One more thing, about noise only commencing once the desktop appears-- it's because audio interfaces (including onboard audio) don't operate until their drivers have been loaded by the OS and they get initialized.
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Re: PSU noise and Windows 7

Postby BJG145 » Mon May 12, 2014 8:56 pm

Goddard wrote:On the the top surface of your motherboard, encircling each of the mounting holes there are earthing (grounding) contact pads or "rings" which serve for electrically connecting the motherboard to chassis ground (your case) and this depends upon good metal-to-metal contact with the heads of fixing screws and thence to the case. Using insulating washers or nylon screws or insulating spacers can defeat this, and although the motherboard will typically still function (as it's also earthed via its power supply connections), it can cause the type of noise you are experiencing (manifesting as "floating ground" noise).


Cheers Goddard. I was looking at one of those rings of contact points when screwing down a motherboard just the other day, thinking: "I wonder if I'm meant to cover them with a washer..."
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