Disconnecting the ground to my mobo's front panel USB header? Tags: ground loop, front panel, headph

Participant · 24 Jan 2011 at 20:51

Hi guys

I have a ground loop when I use my headphones through the front panel of my Lian-Li PC7+. I tried isolating the front panel screws from the case by covering them in PTFE tape which helped somewhat, but I still had a slight hum.

So I did some Googling, then tried disconnecting the front panel's USB connection to the motherboard (at the motherboard end). This eliminated the noise entirely, but now of course I cannot use the front panel's USB jacks (part of the reason I bought the case in the first place).

The cable I disconnected from the motherboard is the one at the top of this picture:

However I have the option of plugging in only some of the connectors:

I've read that the humming / buzzing goes away if you remove the ground connection (as long as nothing's plugged in). This is sufficient compromise for me, as it doesn't matter if it buzzes when something's plugged into the front panel. I can just unplug it when I want to use my headphones.

My question: is it safe to run the USB connection without a ground? What are the implications of not grounding this connection?

Marsman · 24 Jan 2011 at 23:14

I also now have a Xonar DG, and also I had this problem with my Antec case. The USB sockets were linked to the audio sockets with a ground wire, once removed, any noise was gone. Is it possible that within your front panel, the USB is connected to the audio sockets with a ground wire?

PhillyDee · 25 Jan 2011 at 09:25

As long as things work, I would not worry, usually it just so the +5 had a return 0v. Thats all ground is in a PC.

Participant · 31 Jan 2011 at 20:10

Update in case anyone with a similar problem stumbles across this thread.

If the screws are in the front panel connections block, I get static no matter what.
If I glue the front panel on and take the screws out, the noise is all but gone but still there and noticeable with all the USB headers connected.
Needing (or wanting) to use the front panel USB connections and not wanting any overhead nosie, I plugged in the individual plugs (above) and left the ground connections off.

Result is: if there's something plugged into the front USB panel, there's a terrible noise through the headphones...but if there's nothing plugged in, it's absolutely silent. So this is my compromise; I get to use the front panel USB connections, but have to unplug anything before I can use the headphones.

I emailed Lian-Li for some technical input and *shock* have as yet had no reply.