Recently bought a hifi set, with a pair of Elac b6.2 speakers, a marantz PM6007 amp, an elac debut 10.2 subwoofer. and an audioengine D1 DAC. Unless I just didnt notice (which is unlikely), the speakers and amp worked perfectly for a day or two. Now, there is a faint popping sound a few times a minute, coming from both speakers, but not at the same time. I have checked that the wires are all inserted correctly, I have redone the speaker wires in the banana plugs to make sure it is a solid connection. What else could this be? Also, I have one of the speakers sat on top of the amp, is this ok? Thanks.