Alpine INA-W910 AUX Problems

alanwu07

Hi,

I purchased my 2010 Touring used with an Alpine INA-W910 installed. The AUX seems to have some issues as when I put any sort of music through it, it sounds terrible. Not the alternator whine or static kind of bad but completely missing the bass and muffled vocals and barely audible high-end. I'm not sure if this has something to do with any grounds but the audio is perfect when I play music through the USB or radio.

I recently purchased a ground loop isolator and it has gotten rid of most of the problem, but the audio is still noticeably worse than USB even though I'm playing both through my Nexus 5 (USB and AUX-in, same MP3 songs, all in 320kbps if that makes a difference).

The audio after the ground loop isolator is better in that it has bass and you can hear the vocals clearly, but there is still a bit of noise. Anyone have any idea what this could be? I've done a bit of research and it may be just the ground? I'd like a second opinion on this before I take it into a shop for them to check it out. Thanks!