Article: Fix front panel audio EMI noise

I was having a problem with my front panel audio port for a long time until yesterday I found a solution. I am sure many of you have that problem.. So here I start.

SYMPTOMS

While listening either through headphones or speakers through the front panel audio, you can hear a whining noise which varies and you can feel the HDD accessing, mouse movements, scrolling etc. The sound might get worse when you access a USB device connected to the front port such as copy files etc.

Here is a video of the problem I was having.

http://youtu.be/18i_0eWM1do

THE CAUSE

Some cases from reputed brands like Cooler Master, NZXT, Antec etc have the front panel designed such that the front USB and the front audio share a common ground. Here is an example. Image is reference image. May and will differ in your chassis.



As you can see there, both the USB and the audio share the same ground. Therefore, the motherboard EMI shielding no more works as the sound card receives noise from USB signals.

THE FIX

Things you will need.

1. Screw drivers
2. Any sharp object(s)
3. Multimeter(you won't need it if you are absolutely confident-You will soon know what I mean)
4. Access to the chassis' front panel PCB
5. Basic circuit understanding skills
6. Last but not the least - PATIENCE.

Step 1 : Get access to the front panel PCB. Remove the plugs from the motherboard headers and work in a good space.

Step 2 : Carefully understand the circuits.

Switch the multimeter to diode or resistance mode. Connect the probes as shown and you will get 0 or continuous beep value meaning they are the same or continuous.



The exact circuit layout is like this in the PCB I am using for reference



Step 3 : Break the required circuits.



Take a sharp thing like a flat head screw driver or the multimeter probe and continue scratching the circuit until it breaks.

The result



You can coat the scratched area with varnish(for the looks)-Optional

Step 4Now connect the PCB again and reassemble everything. Connect headphone or speaker. If you connect speaker, set the amplifier volume to full. Test using USB drives-copy, move etc, do random stuff.

Here's my result. Beware of some loud Linkin Park near the end of the video.

http://youtu.be/IdfZ80JG2cg

Enjoy.

Not at all, audio is filtered through a different ground with help of diodes. If the chassis Front panel PCB shorts all the USB and Audio grounds, them these problems arise. It is there in other forums too where users did the same thing I did.
And well, it worked for me....

Agreed. Grounding also cause these problems. But that was not my issue. It was absolutely related to the front panel USB activity.

Frick said:

I wonder if there's something else at play, because no front panel audio have never sounded like that for me, with common ground and all.

Click to expand...

It actually depends on the motherboard. I had an Asus M4A88TD M EVO before and never had this problem. With the present one, I had this prob since day 1. I tested with another USB header(disconnecting the original) but used original front audio in my chassis to rule out motherboard issues. No noise was there.

_JP_ said:

Couldn't you just tape (to keep it simple, instead of soldering) one end of a wire to the shield of one of the USB ports and the other end to the case?
Or find a ferrite ring/core and wrap the cord over it?
My case was cheap, but came with one of those and it works.

EDIT: Also, having your front USB ports sounding like a floppy reader is kinda of neat...for nostalgia purposes, of course.

Click to expand...

Tried all of those but none worked. I even ripped off some ferrite rings from broken psus and installed them but got no improvement..
This is actually motherboard related. Better the audio ground filtering, worse will be the noise if the USB and audio grounds are shorted.
And LOL for the FDD like noise.

Refer to my problem thread here.

www.techpowerup.com/forums/showthread.php?t=187149

McSteel said:

It all comes down to how the motherboard grounds USB and what it does with audio ground. Like _JP_ said, you could simply solder a wire to any of the front panel ground points, and run it to the computer case, if your PSU is good and doesn't leak EMI into it's casing (and your computer's case). If it does, you should probably isolate your PSU's casing so it doesn't make electrical contact with your case, and/or run your front panel ground to another suitable grounding object, like the metal construction of your table, or a home heating radiator.

As for ferrite rings, they only work for a specific set of frequencies, and those are dictated by the diameter and the exact material of the ring and the number of turns your cable makes through it.

Click to expand...

True those solutions work for many cases. But that was not my case. I connected a wire from the front USB ground to the metal body of the chassis without any improvement. And there was no problem with PSU. It is totally motherboard related. My old Asus M4A88TD M-EVO never had this problem with the same chassis.

sniperdoc said:

Thank you!!! Had to make an account to thank the original poster on this solution. I have a Thermaltake Level 10 GT case with a front panel audio that has two USB2 ports, a headphone and mic jack, and two USB3 ports. This solution worked perfectly!

It was literally like I was experiencing sounds anew. I heard things I've never heard before, using my headphones. Glad that the ground for both USB sections had their own screws, grounding it to the case. I'm curious why manufacturers don't just do this to begin with. Electrical engineers should know that this would happen... this interference.

OMG... IT'S SO CLEAR!!! xD

Thanks again.

Click to expand...

Glad to find this thread still helping people even after almost 4 years. Thanks for reporting back. Enjoy your headphones.

Schriz said:

Sorry to revive an old thread but this is the best help I have found. I've already tried grounding my mobo and that didn't help. Now I have this apart and am stuck.

Where can I find the schematics or how can I figure out where to cut since mine is different? I'm afraid of doing the wrong thing and making it not work at all.

Click to expand...

Yours seem to be having a separate ground already for the audio. Are you facing this exact problem?

Schriz said:

Yes, lots of audio interference that's dependent on the amount of load. Both front and rear panels are doing it!

Click to expand...

Seems to be a motherboard/audio driver issue than this. Just check once by disconnecting the USB header. If the problem is resolved, then this is the right thread for you. Else you might have to check the motherboard. Hope this helps.