Volume (Gain) for Audio Signal on 3.5 mM jack

[marquardt]

Is there a way to increase the volume leaving the 3.5 mM jack on the BlueStar?

The volume of phone calls is fine (not using the 3.5 mM jack), but the volume of music (streamed via A2DP over the 3.5 mM jack) is a bit low. This requires me to raise the volume on the radio a bit high. If I switch to FM (instead of the AUX 3.5 mM input), the volume is quite loud.

I have the "music" volume as loud as it can go on the iPhone -> settings -> music which is being sent to the BlueStar via A2DP.