[moep]

I would really, really like to use my iPhone’s regular wired headset with Macbook Pro (late 2006).
I know that the old MBPs line-in is not useable for microphones without a preamp so I will probably need to use a USB soundcard.
The thing about those USB soundcards is that they come with two jacks, so I’ll need an adapter that splits up the iPhone’s headset into two male plugs.
Does such a thing even exist or are there any other solutions for this problem that I am missing?

[Cold Warrior]

Is it something like this?

or maybe

[Spheric Harlot]

nope.

The headset has FOUR contacts - L, R, mic, and ground.

If you use any of those regular stereo adapters, you're only getting three contacts, and the mic is shorted out to ground.

I'm not sure if such an adapter exists - you might have to build your own.