I have a question for Casio XW-PD1 Trackformer: When I connect headphones to the PHONES jack of the XW-PD1, the internal speaker switches - as it should be - on mute. When I connect Chinchcabel the Line Out of the XW-PD1 to the XW-PD1 to connect to a mixing console, the internal speaker remains active. Is this a defect or a state of mind? Thank you for your help