Leaderboard

Many headunits will not have distortion when using the rca preouts of the headunit. Usually the only radios that will distort on the rca preouts are the cheaper headunits that are like $150, or if you are using the internal amplifier of a headunit. So being that you have a $400+ marine headunit it's most likely distortion free on the preouts. I just installed a JL Audio MM105 with 12 rca preouts and that is clean all the way up as well.

Don't think Bluetooth has anything to do with it but you can place the same files on USB and see what happens. You could get some different test tones from elsewhere. Also a you should cold reset your head unit before any tests, all setting should be at zero. But as I told you I would test the DD-1 to be working correctly before reaching any conclusions.