M11 arrived today, but when using aux cable only getting audio on left hand side and connection is not stable. I've used the cable with other devices, so it isn't that. I've also tried in with my headphones and in the car, am I doing something wrong ?

Hi newbie on here and need some help. I'll be using a DAP/media player to connect to a DSP amp in my car. The DSP has an optical input. My intention is to download my music to CD quality and use in offline mode in my car. Hope you can help, nervous newbie !