What happens with your "regular" receiver?
Crackling typically when the volume is adjusted (assuming a dial, and not an electronic system) is a dirty potentiometer, or dirty volume control. As time passes, these variable resistors can decay, corrode and become worn. There are methods to "clean" them, depending on your hands on nature.
I am assuming that the noise is there momentarily while adjusting the volume, and does not continue to be heard for the entire song.