it may some form of static build up within your building in the electrical system, as these discharges can cause pops and cracks. for example, when you switch on one deck and then the other, you will hear a slight pop if you mixer is on.

usually if the cart itself has gone, it doesnt fuck about with popping and cracking, it usually just hums until it dies totally.

another thing could well be your speakers dying..?

does anyone else you know have a pair of decks that you can try your carts on to see whether it is anything to do with them?

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MUGGETS

I know its not my speakers because I tried recording a mix the other day and there was a lot of popping and cracking in the mix during some of the more quiet points in the mix (breakdowns, etc.). And actually to be honest, I don't know anybody in my area at the moment that has any decks...I will check into my electrical set up. I might have to many things plugged into the outlet and I also have a cheap surge protector. I will see what I can do! Thanks for the advice!