If a rat dies near a steam pipe, the body wonât dry and the smell can be horrible for weeks. The odor from a dead mouse may last only a day or two. In fact, there may be no noticeable odor from a single dead mouse but several dead mice in the same area could smell for a few days.
Another source of crackling to look at, is the aluminum foil on the amps. This foil is supposed to shield RF and other extraneous noise. But most times all it does is cause unwanted noises. The foil does not make good contact with the chassis and will cause crackling that can come and go. Loose components can also cause some crackling or even the signal dropping out. Some components to look at are pots, jacks, transformers and mechanically connected grounds.
If the noise comes from your amp or it is making intermittent crackling type noises (specially in tube amplification), noises that can come and go or be triggered by certain notes/frequencies or peaks. On an preamp/amp intermittent crackling can be caused by a few different things. The most obvious in the case of a tube amplifier are the tubes. Another thing to look at are the plate resistors. These are the resistors that connect the DC supply to the plates of the tubes.