As far as I know the amplifier is in the base of the aerial that is on the roof. However, when I looked at my aerial in preparation for a safari park visit (damn monkeys!!), mine wouldn't come off. It would unscrew and fold down, but really wouldn't come off.
I'm wondering whether you've damaged the connection that the aerial needs in order to receive the signal? If you put the original one back on do you get your old version of the signal back?
I went back to the standard aerial because having no reception from the C2 one was getting on my t*ts. I also heard that theres a booster of some kind in the base of the aerial...if i remember correctly the threaded bit on the C2 aerial is only really short, so it might not be making contact properly (or something!)