Hello,
you might want to take a look at my reply to this user who had a similar question:
http://www.akg.com/forum/index.php/topic,3728.0.htmlThe guy in the other thread used a laptop computer which should have a weaker signal than most HiFi amps.
I think it is possible that you have damaged your headphones, but they can take a bit of a beating, if you don't do it too often or on purpose.
If in doubt, you might want to try the method I suggested in the other thread (and be extra careful!).
The good news is that your headphones are fully serviceable and you can replace one or both capsules if you really have "fried" them. If you know how to solder, you can do this yourself.
Just have a look at the service documents available here on the AKG page (Pick your model: "S" or "MKII"; the transducer should be the same anyway).
The AKG distributor in your region can order the required parts for you. They will also be able to thorougly check and repair the headphones in case you're not quite sure what to do.
If you do order parts and you have used the headphones heavily for some years, you might want to consider replacing the elastics (the little "rubber bands" that keep tension on the inner headband), the foam disk that sits in front of the transducer and the earpads. They are not very expensive and easy to replace.
Good luck with your headphones... I'd sure like to try the 271. I couldn't resist buying a used K 171 a while ago and I really like the clear and neutral sound (it's pretty much a smaller version of the 271).
Kind regards,
Stephan