EMI noise from front panel audio-Help appreciated

[itsakjt]

I am having a problem. I can hear EMI noise when I plug in headphones to the front panel audio port. It is very low. However, I found out today that when a USB device is plugged to the front panel USB port, the noise increases. I was copying a file to one of my flash drives when I could hear a very disturbing noise. So I opened up the chassis and removed the front panel USB header cable. And the noise was completely gone. To test the motherboard, I connected a different front panel section from an old chassis which has only the USB and no noise was there either with or without flash drive connected. So no problem with motherboard. So I checked my chassis' front panel PCB and it is normal. No damage. I cleaned it and plugged it again and still that noise is there. Anyone got any ideas? Thank you.

 

[Derek12]

Does the current chassis have a metal ring trought the USB or audio cables? I think the metal or thorus thingy absorbs the EMI but I am NOT sure. Also check if they are shielded.

 

[sneekypeet]

google "ferfite ring", then look where you can buy some locally

 

[itsakjt]

Does the current chassis have a metal ring trought the USB or audio cables? I think the metal or thorus thingy absorbs the EMI but I am NOT sure. Also check if they are shielded.

Nope. Just simple wires and a cheap PCB. Thanks for the info.

google "ferfite ring", then look where you can buy some locally

Just did it and I think I can make one myself with those parts from the broken PSUs I've got. I have seen that they have it. Thanks a lot, have to try it when I get some time.

 

[sneekypeet]

Just did it and I think I can make one myself with those parts from the broken PSUs I've got. I have seen that they have it. Thanks a lot, have to try it when I get some time.

Some of the older cases I once reviewed used to ship with these rings in the hardware kits. Seems it is something that has been improved over the years, but every once in a while,there is the odd system or three that just deliver this EMI issue. I think it will take care of the issues, but if you have a few, run the USB and the HD Audio through two different rings.

 

[Derek12]

Nope. Just simple wires and a cheap PCB. Thanks for the info.



Just did it and I think I can make one myself with those parts from the broken PSUs I've got. I have seen that they have it. Thanks a lot, have to try it when I get some time.

Yeah then add one on the audio and USB wires, that should suppres the EMI interference


EDIT: My older computer (5 years ago) had nasty EMI interference through the BACK audio panel that increased with HARD DRIVE activity or SCROLLING so yes, even newer hardware can have it!

 

[itsakjt]

Some of the older cases I once reviewed used to ship with these rings in the hardware kits. Seems it is something that has been improved over the years, but every once in a while,there is the odd system or three that just deliver this EMI issue. I think it will take care of the issues, but if you have a few, run the USB and the HD Audio through two different rings.

Roger that. Have to fix a laptop today so I will hunt for the rings tomorrow and it should be a piece of cake installing those.

Yeah then add one on the audio and USB wires, that should suppres the EMI interference


My older computer had EMI interference through the BACK audio panel so yes, even newer hardware can have it!

Hmm. And yes, I was having this issue for quite some time. Even seen a friend's rig with the same issue but he didn't bother. Today I was really irritated by that noise.

@All- Thanks a lot. Have some drink. Will keep you updated like I always do in my threads.

 

[itsakjt]

UPDATE:
I just ripped off some ferrite rings from old PSUs.

And passed the audio and USB wires through them such that 3 turns were made(can't make more, length of wires limited) and still that noise is there. No reduction also. Is there anything I am missing?

This is a previous photo taken with a good camera.

You can see the cable management and the FP audio(bottom left-rainbow colored) and USB(middle-white) wires. Thanks.

 

[itsakjt]

I FIXED IT! Yaay.

First things first, I was shocked after seeing those rings not sort out the issue.
This was the problem.... I was just gonna post it when the idea came in my mind.

http://youtu.be/18i_0eWM1do

What I did.

I separated the ground between the USB and the audio in the front panel PCB. To my knowledge, they should have different grounds.

Yes, it looks bad. But this is the result. Beware of some loud Linkin Park near the end of the video.

http://youtu.be/IdfZ80JG2cg

 

[Derek12]

Strange, I think computers have a common ground for everything but glad it's solved, anyway, leave the rings, they may help a bit

 

[itsakjt]

Strange, I think computers have a common ground for everything but glad it's solved, anyway, leave the rings, they may help a bit

Yes will be doing it today night.