[R32_Scott]

Silly question. But by AUX connection do you mean you are using an headphone jack lead to an iPod / iPhone / MP3 player?

 

[R32_Scott]

Is your iPhone volume on full?

If you are connected via headphone jack it's just like using a set of headphones, the volume on your iPhone would also control volume. So if your iPhone volume is only half way up, could explain why it's quieter than bluetooth or your SD.

 

[R32_Scott]

Hmm that does sound strange then!