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Digital audio noise from PC

For anything relating to music-making on Windows computers, with lots of FAQs. Moderated by Martin Walker.

Re: Digital audio noise from PC

Postby Martin Walker » Fri May 22, 2020 3:07 pm

James Perrett wrote:Your older PC probably has different internal grounding so it is a bit of a red herring to say that it worked before as that was a completely different situation. You are going to need to break that ground loop somehow and purchasing an isolation transformer is probably the best way to do it if you don't want to go making up odd cables.

I totally agree with this - sometimes you can have multiple ground loops and no digital noises in the background, and then change or add just one item of gear and have a hell of a time tracking down and removing all the ground loop offenders before you cure the problem.

You just have to be systematic and work through them one by one until you have a clean system. Here's a Q & A I wrote some time ago that describes the step-by-step process:

https://www.soundonsound.com/sound-advi ... -my-studio

Hope it helps!


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Re: Digital audio noise from PC

Postby ef37a » Fri May 22, 2020 9:37 pm

https://www.amazon.co.uk/AV-Link-Ground ... th=1&psc=1

That ^ may not be hi-fi but it is not at all bad at modest levels. The main thing is it does the job of galvanic isolation* just as well as the 50 quid jobs and proves the system out.

The leads can be cut, twisted and taped for a test and if that fixes the problem you can get the hi quality unit. If not you are only down a couple of pints of Old and Filthy.

*I would NOT trust one as a safety isolator.

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Re: Digital audio noise from PC

Postby Marbury » Sat May 23, 2020 8:46 am

It's not ground loop humming as such, it sounds like it is picking up electrical impulses from the inner workings of the pc drive and wireless mouse. It's a hi frequency whining sound.
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Re: Digital audio noise from PC

Postby Mike Stranks » Sat May 23, 2020 9:02 am

Marbury wrote:It's not ground loop humming as such, it sounds like it is picking up electrical impulses from the inner workings of the pc drive and wireless mouse. It's a hi frequency whining sound.

Ground-loops manifest themselves in may ways... it's not just hums and buzzes...

I've sorted the noises you're experiencing with an isolator.

But as 'those who know' keep saying, you also need to check out the earthing/grounding on your new PC. Is the case and other bits grounded as they should be?

And, even it they are, you may need additional grounds on some of the kit. I used to have all sorts of funnies with one set-up I used until I discovered that, although electrically safe, the config I had didn't have any grounds at all. I bought a grounding plug, connected it to a spare socket somewhere in the set-up and all problems solved.

As has been said, with noises like this there are very often no quick fixes... you have to track down what's causing the problem and fix that.
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Re: Digital audio noise from PC

Postby ef37a » Sat May 23, 2020 9:44 am

Marbury wrote:It's not ground loop humming as such, it sounds like it is picking up electrical impulses from the inner workings of the pc drive and wireless mouse. It's a hi frequency whining sound.

Yes well, come on chap! That isolator will cost you less than a tenner and even if it doesn't fix THIS problem you never know what might happen/be acquired down the road.

If I were back doing hobby tape recording and AV/PA jobs a couple of those transformer units together with a gaggle of connector adaptors would be permanently in the tool box.

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Re: Digital audio noise from PC

Postby Hugh Robjohns » Sat May 23, 2020 10:17 am

Calm down everybody... this is going around in pointless circles which is almost as unhelpful as Marbury repeatedly pointing out that his previous computer didn't suffer from this problem... :lol:

As a recap for those that haven't been following the previous three pages, and as I understand it (which might be wrong!)... the situation is this:

Marbury has a new PC computer to which is connected a USB bus-powered interface.

Plugged into the headphone socket of said interface is a battery-powered camera.

The problem is that the camera records all manner of unwanted computer-related noises.

If that description is valid, there really can be no possibility that this is a ground-loop problem as only the PC is (supposed to be ) earthed.

From the above evidence I'd actually posit that it is far more likely that the PC is not grounded at all, or not grounded effectively.

And that's definitely where I'd be focusing my attentions if it was my system...

But to complicate matters slightly more, the stereo headphone signal is being fed into a stereo microphone input of the camera (with plug-in power), so we may have a problem with excessive gain, and or an AGC working overtime, and or plug-in power upsetting output drivers.

I have already suggested the simple expedient of seeing what happens when a good solid ground is provided to the interface or camera, but I haven't seen the result of that experiment posted anywhere in the thread yet.

...Now... please show your workings on the paper provided and discuss.... :lol:
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Re: Digital audio noise from PC

Postby ef37a » Sat May 23, 2020 10:48 am

Yes! Mr Mainwaring.

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Re: Digital audio noise from PC

Postby Hugh Robjohns » Sat May 23, 2020 11:19 am

:D ....stupid boy.... :lol:
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Re: Digital audio noise from PC

Postby ef37a » Sat May 23, 2020 12:03 pm

Hugh Robjohns wrote::D ....stupid boy.... :lol:

No, that's (don't tell him) Pike.

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Re: Digital audio noise from PC

Postby Mike Stranks » Sat May 23, 2020 1:15 pm

Hugh Robjohns wrote:Calm down everybody...

I was never un-calm... in this thread anyway! :lol:
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Re: Digital audio noise from PC

Postby Marbury » Sat May 23, 2020 2:39 pm

I would also point out that the sound comes out pretty loud through my Absolute 2s via a Samson servo 170. Again, as I need better monitors, would I be better just getting self powered ones to cut out the amp ? This could solve it. I do recall now thinking about it that my old pc did have these problems but I can't remember how I got rid of it. failing everything, I will get the gadget Dave has suggested from Amazon in the hope to stop it.
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Re: Digital audio noise from PC

Postby ef37a » Sat May 23, 2020 3:06 pm

Marbury wrote:I would also point out that the sound comes out pretty loud through my Absolute 2s via a Samson servo 170. Again, as I need better monitors, would I be better just getting self powered ones to cut out the amp ? This could solve it. I do recall now thinking about it that my old pc did have these problems but I can't remember how I got rid of it. failing everything, I will get the gadget Dave has suggested from Amazon in the hope to stop it.

I don't know your budget but if you can run to the Neumann KH80s they use a fig 8 earth free mains connector. Several other active monitors have gone that earth free route as well.

Mind you, having too much stuff without an earth can bring its own problems.

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Re: Digital audio noise from PC

Postby Hugh Robjohns » Sat May 23, 2020 3:41 pm

Marbury wrote:I would also point out that the sound comes out pretty loud through my Absolute 2s via a Samson servo 170.

Ah.... I thought we'd established that the noise happens when nothing else was connected to the interface apart from the camera?

If it's there with the Samson connected (and not when it's not) then we could be back to a ground-loop... I'm getting dizzy!

...would I be better just getting self powered ones to cut out the amp ? This could solve it.

It would be very strange magic if it did!

I do recall now thinking about it that my old pc did have these problems but I can't remember how I got rid of it.

The one thing that is vital when fault-finding this kind of issue is a clear and logical line of thought and accuracy of information.... :think:
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Re: Digital audio noise from PC

Postby Marbury » Sat May 23, 2020 7:25 pm

I might go for the Neumann KH80's to solve 2 problems of needing decent monitors too. Looked at some youtube videos and very impressive.

I will also say that the noise is not showing listening via the phones out on my Shure SRH840 headphones.
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Re: Digital audio noise from PC

Postby Martin Walker » Sun May 24, 2020 2:15 am

Hugh Robjohns wrote:The one thing that is vital when fault-finding this kind of issue is a clear and logical line of thought and accuracy of information.... :think:

Which is exactly why I posted the link to my step-by-step guide above :headbang:

Come on Monsieur Marbury - you've only got to do this once, systematically, and solve the problem once and for all.

Even if you find you need an audio isolator of some sort as has been mentioned, there's no point in plugging one in willy-nilly - following the step-by-step guide should enable you to find the culprit (or culprits - there could possibly be more than one), and then you'll know exactly where to place your isolator if one proves necessary.

Here's the link again: https://www.soundonsound.com/sound-advi ... -my-studio

And I should also point out that I did provide a description of most possible ground loop nasties in it, namely:

"Problems range from straightforward 'hums' (which normally include various levels of the mains harmonics, such as 50Hz, 100Hz, 150Hz, and so on in the UK, or 60Hz and higher multiples in the US), to a wide range of scratches, ticking, buzzing and other digital gremlins that are often associated with computer activities such as graphic redraws, mouse movements, and hard-drive activity."

The feelings of relief that that you'll get once the problem is solved will more than outweigh the effort in tracking it down ;)


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