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 Forum index » Instruments and Equipment » General Discussion
Fixing ground noise
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Regebro



Joined: Sep 12, 2004
Posts: 32

PostPosted: Sat Aug 12, 2017 4:08 am    Post subject: Fixing ground noise Reply with quote  Mark this post and the followings unread

I built a new computer, with a new nice power supply from a known company and everything.

Buuuuut, as soon as I turn it on, noise comes out of my speakers. This happens every time I have any form of ground connection between the computer and the rest of the setup. (I have a mixer, various equipment connected to that, and powered speakers connected to the mixer).

It's not ground hum (I get that if I connect anything to a set of power-plugs on the other side of the room, though, so I don't).

Why does this happen and what do I do?

Edit: I thought it was a ground connection via the power cable, but it was not, I had missed a USB cable. No, it happens when you connect some sort of chassi ground.
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Regebro



Joined: Sep 12, 2004
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PostPosted: Sat Aug 12, 2017 9:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Could lifting he ground of the PC work?
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Regebro



Joined: Sep 12, 2004
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PostPosted: Sun Aug 13, 2017 12:40 am    Post subject: Reply with quote  Mark this post and the followings unread

The answer was a "yes". Putting a ground-cheater plug in the computer made that noise go away.

I looked around for a plug that lifts the ground in a better way than just disconnecting it, but I can't find one. Hints are welcome.
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Blue Hell
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PostPosted: Sun Aug 13, 2017 4:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah yes, USB sucks Confused

There are USB isolators - such a thing would break the ground loop too. Something like : http://www.bb-elec.com/Products/USB-Connectivity/USB-Isolators/USB-Isolators.aspx

You can also get ground loops from MIDI stuff that is not up to specs btw (MIDI should be grounded on one side only, sometimes both sides are).

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DES



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PostPosted: Tue Aug 15, 2017 6:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Tripp Lite used to sell an isolator/filter that you plugged into the wall then plugged your equipment into it.

Is the power supply a line-lump/transformer type or is it a desktop style in-the-case type? If the later I would be raising a lot of noise with the manufacturer...it should not be putting noise on the AC line or ground. Who was the power supply manufacturer?

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Regebro



Joined: Sep 12, 2004
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PostPosted: Tue Sep 05, 2017 1:56 am    Post subject: Reply with quote  Mark this post and the followings unread

It's a Thermaltake, shockingly. It's one I had lying around, more or less unused but out of warranty. Can't be bothered to change it, too much work.

Yikes, isolators are expensive!

I'll go with just lifting the ground. Cheap and works. Smile
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mode



Joined: Sep 30, 2017
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Location: SE England

PostPosted: Sun Oct 01, 2017 3:51 pm    Post subject: Re: Fixing ground noise Reply with quote  Mark this post and the followings unread

Regebro wrote:


Why does this happen and what do I do?



Could be your LCD screen. Your post reminds me of why I stopped using mine with my laptop.
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Regebro



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PostPosted: Wed Oct 04, 2017 2:59 am    Post subject: Reply with quote  Mark this post and the followings unread

No, I get it even with the screen unplugged and disconnected. When I get time I'll try with another power supply.
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mosc
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PostPosted: Wed Oct 04, 2017 10:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Computers, especially laptops, are notorious. I use ground lifters on ALL the power connections in my studio. Actually, I break the ground connections on every power cord. Do this and you will never get any hum.

Except, some USB gear is poorly designed and when you hook it up you get nasty hum and noise. As Blue Hell said, a USB isolator will work wonders. It's not just cheap equipment that has bad USB circuits. I have an Allen & Heath mixer that requires and isolator.

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Blue Hell
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PostPosted: Wed Oct 04, 2017 10:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Ah no, not only cheap USB stuff does it, actually it is behaviour "designed into" USB, the standard was not made for studio audio but for gadets rather ... being grounded on two sides it's just asking for trouble... firewire is (or was, rather) better, ethernet is OK too.
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Regebro



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PostPosted: Sat Nov 11, 2017 7:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Finally today I switched from the Thermaltake to a BeQuiet. Problem solved.

I only use USB for MIDI, maybe that's why it works. Smile Now I only get noise from the computer working on my audio outs, but I'll guess I have to live with that until I decide to mix in the computer and ditch the mixer.

I did discover that my OSC OSCar also creates a ground loop (after I changed to a proper plug so it's actually grounded), I suspect the power supply there as well. Old electrolytes perhaps?
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