2016 head unit FM radio much louder than I-phone music via USB

[oliver_reid]

When I connect my I-phone 6 to the USB-in, I have to turn the volume up to get a decent level.

If I switch back to FM radio the sound is so loud it blows me out of the car if I forget to cut the volume first.

Any way to adjust the relative volume of audio sources?


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FYI I have removed the BOSE amp (which sucked) and the head unit line outs connect to a replacement amp

 

[tinman831]

You may need to adjust the volume on the phone as well to get it louder.

 

[xcessiveforce]

I believe this is due to the preamp that's built into the head unit. It will be louder for the FM\AM\HD radio as well as the Aux input and much lower for the Bluetooth\USB. I'm just guessing but I can verify that I receive this type of result in my new CX 3.