IMac digital out help

I recently purchased an imac to feed my audio aero capitole and use it as the DAC. In order to get the digital out i was planning on going toslink and got a mini toslink adapter thinking that the headphone jack is hybrid. To my surprise the mini toslink is quite smaller that the headphone jack. Is my output not hybrid? Do i have the wrong adapter? Should I pursue a usb or firewire digital out instead? Any help would be great.
It is hybrid. Not sure what adapter you got. I use this and it works fine.
This is the adapter i used. Still confused...
How old is the iMac? Are you sure you are using the audio output?
the imac is brand new. The plug is way too small. Apparently it is 2.5mm which is smaller that the standard 1/8" headphone plug. I don't know what this plug will fit but not my MAC. Weird.
You just need a mini toslink adaptor or cable.
i did buy an adapter. Check out the link a few posts above. I just happens that the mini is smaller than a 1/8" headphone jack. It looks right, but I guess it's for something else. Bought a cable from Dedicated Audio already to get this overwith.
@Quaded: I have looked closely at the link you posted, and I do not know of a Monster Cable product like that. In fact, I question if the adaptor you purchased is an "authentic" Monster Cable product. I've never even heard of a "2.5mm-toslink adaptor". From the photo, it doesn't even look like the 2.5mm plug has an optical end.
Got it from pro cables direct. Looked legit, but I'm still confused as to what it does. Here's the link.
@Quaded: I've never seen such a item, and have no idea what it could be used for. If it's just an analog 2.5mm end, then it would have to have a DAC for conversion to digital toslink. If it's a 2.5mm optical, then I want to know what uses that kind of plug? I am not aware of such a thing?

When I Google that part number, I only get that page, for that site for your link. I wonder what it is? Does anyone know what it is?
When I first got my Mac Mini I used a mini-toslink cable from Van Den Hul. Conventional toslink on the dac end and mini-toslink on the Mac end. Sounded wonderful. I've since moved to firewire, but the VDH is still wonderful.
One more thing: Don't buy adapters of any kind. The VDH is glass optical as well, so it truly is a great sounding cable.
Thanks. I'll look the VDHs up.