Motorola E815 / E816 Hollywood

I have the stereo headset adapter so I can play my mp3 files that I've stored on the phone through a pair of regular stereo headphones (sound is great, by the way). However, when I try using the adapter with a cable to plug into a pair of AUX amplified speakers, the phone's internal speaker comes back on (it's usually disconnected when you use the headphones) and no sound is supplied to external amplified speakers. Any suggestions.

Thanks

Brian