The volume level from the aux input cable I just installed is very low. I know that the 1-6 buttons change the gain, but even at 6 the volume is lower than any of the other sources. This is with the mp3 player volume all the way up, which sounds even worse because it is clipping. In reading all about the aux input, I've never seen this problem talked about before. Is this normal? Is there anything I can do?