I had a read of the thread and not knowing the Linn Majik1 personally looked for some pointers on the net came across this from What-HiFi review " the Majik-I isn't so skilful at delivering very low-level detail or the natural richness in a recording. Even a full-bodied disc such as the first The Lord of the Rings OST sounds overly dry and just a little clipped. There isn't he space, low-level detail or bass power we'd expect at this price." now this could be due to the power side of the amp and I take note that you are using it as a Pre-amp, but some aspect may be due to the pre-amp side. I cannot find anything about the SQ of it built in Phono Stage, but there is a board upgrade from Linn for MM/MC which implies it can be improved on and then support MC as well.
My view would be to initially borrow a reasonable Phono stage and try it and see if there is an improvement, there was a Cambridge 541on sale here for only £65, it cheap as ships and they are good. If you get no improvement then try another cartridge or mew stylus as others have said and make sure it is set up correctly, there here are several thread on here on this on VTF and VTA. If you still have no joy then I would suggest you try an borrow a pre-amp or home demo one and see if solved.
I hope that helps.