Sound problem e39
 

Hello , i have a bmw 525iA from 2001 with Hi-FI without DSP with NAV and i have a problem. The sound is stoping in my car and to make it work again i must change the song (from the cd i mean) , or to close then open the sound.This is happening at TV , radio , cd. (i didnt try the tape). It stops doesnt metter of speed or anything , its simply stops no metter what.I thoght the amp its broken , but yesterday i put an sub woofer in my car , and i took the signal from the AMP LINE IN not from LINE OUT that goes to my speakers , and now the music stops if i want to hear louder , still stops (but its working more) if i listen to low volume.The thing is that (i think) not the AMP is doing trouble to me becouse if the AMP whould fail , my subwoofer must work(becouse it wired before on the AMP IN not OUT) , and its not working.So what can the problem be? Sometime (before adding the subwoofer) worked 1 2 day with no problem doesnt metter of volume i was using , and had some time when it was not working (every time i restared the sound to have sound again) , now after i put the subwoofer when i want to listen loud it stops and i must resart the music. Anyone here can help me?