Well, it's a first time I hear about a headphone jack being weaker than line out... But in today's world of cheap ass technological wonders everything is possible. Afraid that the only option you have then is to mess with rechargable batteries. Not that you haven't thought of that either but tragically that is all that is left.

Another option would be to trash the damn thing and get something better. But you have to be able to afford that. I had to do that with the audio interface for my new Mac. I picked up an Edirol and was getting a very weird noise on the main outs. Not very common for Macs. Noise and crap of that sort is usually a PC thing. However the only solution to the noise problem was a more expensive audio interface. I went with MOTU 828. Works like a charm now.

So unfortunately there isn't a lot you can do about this bizarre problem that you're having with your MP3 player. If you can only connect the AC to charge the batteries then I guess you can't really use one to power the thing. I'm just wondering why they didn't just ****ing give it a normal AC power supply. I mean most people would try to do what you're trying to do which is connecting it to external amplifiers and systems. That is why they gave the damn thing a line out jack right?

Personally I don't mess with that kind of stuff. If it ain't pro stuff I don't touch it. Used to , but had enough!!!

-ED-