**UPDATE**
Just released is the new Xbox 360 console which includes an optical out (toslink) port on the back, and as soon as I can, I'll include some audio setup screenshots.
It took me WAY too long to get a set of Tritton AX 720 5.1 Surround Sound gaming headphones
to work with my already hooked up with HDMI
, Xbox 360
.The instructions say to plug the headphones into the optical out on the back of the Xbox 360, which I did. In my case however, I could not hear the sound from the headphones.
The answer was this.
Instead of plugging the amplifier box of the headphones into the back of the Xbox 360, I plugged them into the optical out on the back of the TV. Means you can leave your HDMI doing its thing with your 1080p crisp digital display, and not have to resort to endless wife-annoying cable swaps each time you want to do something different with your console.
This meant that I now get the sound from the headset, as well as from the 5.1 speakers, or TV if I switch those speakers off. So just turning off the speakers, and then turning down the TV, I get it only from the headset. So I could have saved the few bucks it cost to get the audio dongle for the Xbox 360. I couldn't find any reason why I should not have been hearing the audio from the headphones, as on the Xbox 360 settings only showed 5.1 or stereo output, not the actual port you want to output from (as the PS3 does). Perhaps I had a faulty audio dongle, we may never know.
In my particular case this is a little fiddly as I have a PC, PS3, and Xbox 360 all hooked up to the same screen, and to use the normal 5.1 speakers it takes the optical out from the TV (for the PC sound). So each time I want to use the headphones with the Xbox 360, I have to unplug the cable that runs to the 5.1 unit from the TV, and replace the cable with the one going to the Tritton AX 720 headphone amp. It's not too bad because there is enough space to walk behind the set so swapping a cable only takes a moment. Also I have to plug the headphone amp into which ever console I'm using anyway, so perhaps I am bitching a little too much here, but I do sympathize with those of you that (as most people do) have NO SPACE/LIGHT AT ALL behind their TV sets. I could get into some seriously tedious optical cable splitting, but I'd need one for the back of the TV, and one for the back of the headphone amp, it's not really worth me doing that.** (Update - I think I'm wrong on the splitter thing, as it makes TWO optical connections, but doesn't switch between inputs.)**
Does the Xbox 360 route audio through HDMI only, if it finds that connection first?
In my experience the PS3 works just as the manual says.Overall on both consoles, the effect is pretty stunning and I am surprised I really get a sense of surround sound from just a set of headphones, plus there's a lot of bass in there too.
Red Dead Redemption
got a lot red deadier with these serious cans on my head.Just to be clear, when I mention headphone amp above, I am referring to the little box that comes as part of the Tritton AX 720
headphones. 
