My left channel in the Miata had been intermittent for some time and eventually the radio displayed “AMP ERR” and stopped playing music entirely. When I ordered the unit and install kit from Crutchfield they included a Scosche line converter which converts the speaker outputs from the head unit’s amp into line-out signals for the amplifiers built into my Miata. I thought nothing of this and simply installed it as you would.
To put this another way, what I was effectively doing was taking a digital music file, that would be converted to analog and pushed out the head unit, converted again to a line signal, and then amplified again and sent to the speakers.
But this head unit has line outs on it.
So I cut up an AV cable and stuck the plugs into the wiring harness, getting rid of the bulky broken Scosche converter and getting my music back. Sounds slightly better due to less electronics between my flash drive full of music and my speakers.