Hmm... That doesn't sound good at all. Crackling and popping could potentially be murderous on your speakers. Does it happen during certain musical passages, or just randomly?
If it's random, it could be dirty power going through your electronics, such as when someone in your house or neighboring house turns on or off a blender, vacuum cleaner, or when the central heating/air kicks on or off. All of these types of things can cause an electric surge that some electronics are more sensitive to than others. Many people run their components on power supply filters for this reason.
Hard to say without actually hearing it.