PC HD audio front panel rewiring + EMI filtering - Page 1
Forum section: electronics / beginners

author: Agony
author_rank: Contributor
timestamp: April 23, 2013, 07:11:29 pm
content: 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.

author: Agony
author_rank: Contributor
timestamp: April 24, 2013, 02:31:20 pm
content: Bump. Anyone got any tips for the EMI filtering?

author: c4757p
author_rank: Super Contributor
timestamp: April 24, 2013, 02:43:12 pm
content: 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.

author: Agony
author_rank: Contributor
timestamp: April 24, 2013, 03:03:37 pm
content: how abut also looping the front panel cables through a ferrite ring to reduce/smooth unwanted spikes and pulses?

author: c4757p
author_rank: Super Contributor
timestamp: April 24, 2013, 03:20:43 pm
content: 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 youdon'tdisconnect the grounds and justadda 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 putbothcables through the same ferrite or you're just making a transformer...

author: Agony
author_rank: Contributor
timestamp: April 24, 2013, 04:35:32 pm
content: 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.JPGAnd 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

author: c4757p
author_rank: Super Contributor
timestamp: April 24, 2013, 05:12:44 pm
content: Quote from: Agony on April 24, 2013, 04:35:32 pmI don't see where they're shorted, and I can't imagine they are. Can you elaborate?

author: Agony
author_rank: Contributor
timestamp: April 24, 2013, 06:15:25 pm
content: the short was is with pin 2 and 4 on the mother board side connector.2 is labeled as Analog Ground4 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.

author: Monkeh
author_rank: Super Contributor
timestamp: April 24, 2013, 06:32:16 pm
content: Quote from: Agony on April 24, 2013, 06:15:25 pmNeither pinout you have is correct.http://www.intel.com/support/motherboards/desktop/sb/cs-015851.htm

author: Agony
author_rank: Contributor
timestamp: April 24, 2013, 07:42:47 pm
content: That one explains the 2-4 connection.