Logan Lamothe follow the instructions in your manual. If you do not have one, you can download it at places [link|https://www.manualslib.com/download/242621/Sony-Dvp-Fx810.html|like this]
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You need to check/set the side switch LINE SELECT IN OUT and see if that changes anything. Of course you also have to make sure that your AUX cable is compatible. Double check the manual for all of this.