aux amp

[djh3]

On a recent trip I had a splitter for my Aux input so I could run the GPS and Pandora off my phone. The volume from the GPS was fine but I couldnt seem to get as much out of the phone, even turned way up. I did have my boosteroo with me and tried it but that didnt seem to help much. Is there any kind of amp that can be installed inline or the like for the Aux inputs? If I turn up the phone volume to say the very top the out put get sort of distorted, so I have to give it a couple clicks down. But then you have to run the volume on the bike @ 28-30 to hear it at 70mph.