stereo audio volume problems

[bibbyso]

Hi I thought i would try here not having much look.The problem i am having is with my 406 the radio now works after changing a blown fuse in the back of the radio but i have very low sound and only seems to come from the rear speakers.The cd changer is not present and have checked there is a amp under the sat nav unit.All fuses look ok in the fuse box and the radio seems to function correctly apart from the obvious volume problem.
I wanted to check the amp but it looks a little hard to get at and i am not the best with cars.
Any ideas would be much apprectiated as i dont want to start buying replacement bits and pieces if there is an obvious answer to my problem
Finally would an auto electricion be able to help with this problem
Thanks for reading this and thanks in advance for any help offered