If the problem stayed in the right speaker when you did that, and given that you've tried a different set of speaker cables, and assuming that there has been no crackling from the left speaker at any time, there are only two possibilities that occur to me:
1)The speaker has a problem, as Brf and Lew suggested. Perhaps there is a short in the speaker, that is causing the amplifier to have problems that in turn result in it supplying a crackling "signal," even when no music is playing.
2)The cable going to the right speaker is in close proximity to some source of radiated interference (RFI/EMI), such as a power cord, and that interference is entering the feedback loop of the amplifier (assuming it has one), and causing the amplifier to output a signal which causes the speaker to crackle.
I don't see how the problem could be caused by a defect in the amp or the preamp or a source component, given the findings you've described.
Regards,
-- Al