Noise when using Front-Panel headphone j

Question

This message is for those who may experience noise in headphones plugged into a case's front jack. These noises would likely be heard if one uses a quality phone set with good isolation. (not noise cancelling type) and during quiet times, such as when no music or other audio source is being played, or perhaps when listening to programming with very high dynamic range and the frequent, very low loudness passages of music, etc.. There is no problem with the card. (I'm using an Xtreme Gamer card) The problem will be with the header panel on the case itself. You need to isolate the case ground from the other grounds coming in from the various board headers, such as USB, the sound card, etc. I accomplished this by scraping away the foil from around the stud landings on the panel module board. Of course you need to exercise care when performing such a modification but you will be rewarded with absolute, golden silence, when that's what you should be getting. Again, there is NO problem with the card.

Answer 1

If it is possible to remove the circuit board assembly for the front panel jacks from the case, you can see how the circuit foil "traces" on the board are connected. In my situation, and probably yours, you may find that the mounting screws that hold the circuit board to the computer case will also have the foil traces under them and that those traces will be a common ground to the rest of the circuits on the board. The problem arises because the computer case ground is at a somewhat different "signal" level than the grounds coming into the circuit board from the various "header" connectors, that is, the connectors you mate with the corresponding pins on your sound card, as well as the USB pins, if you choose to hook them up too. There is a great deal of strange noises that can be present in a given motherboard's circuits and associated grounds. All the ground connections from the headers coming into the board should only go to the individual connectors on the front panel. I cut away the foil paths where the grounds were all run together on the circuit board, thus isolating them from one another, as well as cut away the foil under the mounting screws. You may even have to cut foil from both sides of the board, depending on your model. You need to take care not to open up a circuit when making those cuts. A good, sharp Xacto knife or utility knife should work fine.
I found it strange that the designers of the board didn't consider the problem of "ground loops", which is what the problem is defined as. Ground loops, as you can see now, can happen when when a circuit or even separate components altogether, such as a computer, TV and HIFI system are all connected together. In the?HIFI setup case, hum results because the point of incoming cable ground for your TV and/or Internet are at a different 60 Hz voltage from the ground in your home's wiring,?to which your computer is connected for power. This causes a current to flow through the audio cable shields that is large enough to induce a voltage into the audio equipment. I've even heard of ground loops so bad that people have seen sparks when trying to hook up the audio cables between the pieces of equipment. Almost anyone who has a system hookup such as I described has run into that problem of hum when using their computer's audio into their HIFI setup. The only relief is to get some type of ground "isolator" that connects between the incoming cable and your TV and/or Internet cable modem. A quick and dirty solution is to use a grounding adapter in the AC connection for your computer and other equipment that uses a grounding plug. This, of course, is not recommended, but will kill the hum for now. I thought I would throw in the HIFI setup hum problem since, as I said, many people are suffering from that problem.
Even if the header grounds were all shorted together, the problem would be no where near as bad as having the case ground shorted to the header grounds, which was the way mine was made.
I know this is a looooonnnnnng winded post but trying to explain something like this in writing is not easy. Hopefully you will now have a better understanding of what I meant the first time, even though it was by no means a short post either.