PC HD audio front panel rewiring + EMI filtering

[Agony]

First i am green in electronics (practical side) - iv watched, read and  got decent knowledge on the theoretical side but lack of funds, locations (no decent shops to even buy anything within 50km) has limited my practical side.

Problem is the PC cases front panel -  old case had no issues with static noise, so the motherboard is fine.

The new one however has the ground  same as the USB ports - really idiotic design idea.

So i could physically sever the audio/mic from the USB GND. Now for some reason - it doesnt use the HD Audio GND pin itself () so id have to rewire/solder somen of it (cutting physically some tracks on circuit etc).
Now however, while at it - i was thinking of a simple, easy EMI filter of some kind - since its close to USB ports that generate fair amount of noise when connected.
Thats where i get stuck - what would be the simplest way to add some basic EMI filtering there?




Altho i will test the pins and  the motherboard side cable pinout to make sure that each pin is what i guessed it will be.

[Agony]

Bump. Anyone got  any tips for the EMI filtering?

[c4757p]

Don't bother. Just rewire and you should be fine. One other thing to try is to replace the cables themselves. If I remember correctly from my case that uses the same board, the cables that it provides are just loose wire in a tube. Using the right cable (shielded audio cable - perhaps chopped from broken headphones - and shielded, twisted pair USB cable) should not only improve the sound but the USB throughput as well.

[Agony]

how abut also looping the front panel cables  through a ferrite ring  to reduce/smooth unwanted spikes and pulses?

[c4757p]

Putting just the audio cable through a ferrite may help encourage the faster USB signals to use only their own, lower-inductance ground line, but I don't think it will help much.

Edit: Of course, that's if you don't disconnect the grounds and just add a ground in the right place. If you actually cut traces and separate the grounds, put the ferrite on the USB cable to dampen the edges and reduce capacitive coupling, but I still don't think it will help much. Separating the grounds and using the right cables should, though.

Don't put both cables through the same ferrite or you're just making a transformer...

[Agony]

right pulled it apart again to take a new look a pinout and the tracks.

The pins for the upper row of the connector on pic, the middle one above the empty/no pin is linked to the  VCC according to the intel hd audio pinout - that in return is connected to GND on the connector itself via a small jumper wire.

http://www.dfi.com.tw/Upload/FAQ/CM/images/HD_Audio_pin.JPG

And the same pin actually WAS connected to the GND of audio alredy - But sharing the same common GND traces across the board.

Just wodnering now tho - why is the VCC and GND shorted like that Oo

[c4757p]

Just wodnering now tho - why is the VCC and GND shorted like that Oo

I don't see where they're shorted, and I can't imagine they are. Can you elaborate?

[Agony]

the short was is with pin 2 and 4 on the mother board side connector.

2 is labeled as  Analog Ground
4 is Analog VCC.
Both were shorted via a short black wire on the connector and the VCC wire run to the front panel.

But it works. Had to cut and rewire more - even the pins shared common ground so needed to separate the pins aswell.
Nice and silent now.

[Monkeh]

the short was is with pin 2 and 4 on the mother board side connector.

2 is labeled as  Analog Ground
4 is Analog VCC.
Both were shorted via a short black wire on the connector and the VCC wire run to the front panel.

But it works. Had to cut and rewire more - even the pins shared common ground so needed to separate the pins aswell.
Nice and silent now.

Neither pinout you have is correct.

http://www.intel.com/support/motherboards/desktop/sb/cs-015851.htm

[Agony]

That one explains the 2-4 connection.