Turtle beach X12 making a subtle HISSING sound

Turtle beach's hiss troubleshooting. This isn't what I experienced, but it might help some people that reach this question. To sum up, three possibilities:

1. This is an amplified headset. Amplifiers amplify all sound (including noise) originating from the source. Solve by turning down the amplifier and turning up the source. (this isn't you, as you hear the hum with a silent source).

2. XBox controller talkback wire. Disconnect it to see if the hiss goes away. (no long term solution presented other than leaving the wire disconnected).

3. Microphone noise being sent back to through the headset to your ears (I think if this was happening, it would be obvious). Mute the mic to diagnose.

So I did some more googling and found out about Ground Loops.

Ground loops created by improperly designed or improperly installed equipment are a major cause of noise and interference in audio and video systems. They can also create an electric shock hazard, since ostensibly "grounded" parts of the equipment, which are often accessible to users, are not at ground potential.

And then I found Turtle Beach's Ground Loop article.

Perhaps an electrical engineer can give a better description of the problem, but from what I understand, the headset is connected to two devices (the console and the tv). These devices don't agree on what zero signal is, so when the TV's zero signal is viewed from the console's zero, it's not zero any more... not zero = signal = the noise you hear.

The articles recommend introducing a two prong adapter to diagnose the issue, but no long term solution is given.

You may also want to watch this guy talking about ground loops:

In addition to Amy B's excellent answer I would just add a few things from my experience that may help you.

1. Some headphones are "noise cancelling". The "cancellation" is actually caused by sound emitted from the headphones that is intended to destructively interfere with sound outside the headphones. Generally this sounds is design for you not to hear, but sometimes you can hear it when it is quiet. I don't think Turtle Beach headphones provide this feature, but I'm not familiar with your particular model.

2. Audio grounds are tricky like Amy B points out, but you might be able to get improved results by getting all connections to a common ground. This would be possible by:

a. Connecting the USB power cable to your TV, if your TV is digital and has a port.

b. Routing audio to your PC, and connecting USB power to your PC. Your PC will need Red/White audio ports (typically on a PCI adapter card), or you can get a Y dongle that converts the Red/White audio to the single PC stereo jack. In this case you would want to make sure you connect it to an input port (mic, line in). This may sound complicated, but it is the set up I personally use and once you figure out inputs and outputs its pretty straightforward. It also has the advantage of letting you listen to PC and Console sounds from one pair of headphones.

c. As a somewhat longer shot, you could kludge a ground cable connection between your XBox rear panel, and your TV rear panel. You should be able to just touch the wire between the two panels and listen. If the hiss goes away, you can make a more permanent connection.