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.
quaded
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.

http://www.procablesdirect.com/p-65-monster-25-mini-to-optical-toslink-adapter.aspx
@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.