Car Stereos: Alpine premium audio system, jaguar x type, alpine system

Question
I have an '03 Jaguar x-type with a factory Alpine system.  Everything has been fine until now - the voices are very quiet while the bass is very loud...all the speakers work and the volume works except only to make the bass louder.  This seemed to have happened after I got the car back from the auto repair shop when they fixed my oxygen sensor under the hood...what could it be?  Is it the radio or the amplifier?  I'm not sure what I should be getting repaired.  I do not want to take it to the dealer.  Any help on this is really appreciated.

Answer
It sounds like the amplifier might have gotten a short somehow.  There is built in crossovers to send the right power to the right speakers.  The high pass end of the crossover must have a bad spot, and it is not letting the highs through.  There will be a minute bit flowing over from the bass filter, but for the most part, only the lows will be normal sounding.  There may be a slight chance that a fuse has blown, either in the fuse box or on the amplifier itself.  The only other possibility is if the system only uses the amplifier to power a subwoofer, and the radio powers the main speakers.  The amplifier in the radio would be the problem, and the amplifier is still working properly.  This would be the case if your car has a designated subwoofer.  Otherwise it is as I mentioned above.  Hope this helps, Scott