Hello Neil,
I just found this thread as its been a long time since I've been around.

FWIW, you don't need to convert a thing, just grab a proper headphone jack from Ratshack to hook up to the binding posts on your amp so you can plug your phones in.

I used my SE84CSEX to drive my Sennheiser HD650 phones to VERY GOOD effect. Since the AKG ( I presume ) phones are even lower impedance, the synergy should be even better. I believe you will be VERY SURPRISED at the sound quality of that combo.

There are some things you can try to make it even better. Let me know if you've taken the plunge yet. If not, do it, and then we'll talk.

Cheers, Crazy Bill      :)