I’m Confused

Alto ZMX 862 Sounds Tinny

So I just got an alto ZMX 862 today, and went to try it out. I just played music off my phone, into a 1/4 line inputs 3+4, but the sound is very tinny and at loud volumes, the sound starts to crack. It also has trouble with bass, mixing the two channels together, if I pan it to either side, it sounds better, but I obviously can't use it like that. Please help.
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