Sennheiser supplied a replacement power supply for my Sennheiser headphones.
However I was unable to use it as it was physically different from the original power supply though the output voltage was identical.
On the web page I saw a picture of the old model which looked like my old charger and I thought that's the model I would be getting and it would be a simple matter of transferring the Australian plug onto the new charger.
Sennheiser then sent me the Country Adaptor Set for the newer model at no charge which was very nice.
Headphones work extremely well. Can watch somehting on my laptop whilst others are watching TV.