We just bought an AP-450 and were using it in the settings it arrived with. When I was playing a few days ago the sound suddenly changed. Now the volume needs to be higher to hear the piano and it sounds more hollow. I am worried something broke in the piano, but it could be that a settings changed (my kids touch the piano). Is there a way to return to default settings? Is it normal not to hear the piano when the volume is turned so that the volume line is even with the power button? Thanks, Jenn
