I believe I am having a similar problem I get similar results with all my guitars, and no it's not electrical interference. Also, the earth switch makes no difference. I've made some sample clips, clean and distorted, here: The noise is even more noticeable through my CLR cab than though my DAW.
Hard to say since I haven't done any recording for a while. I think the answer is to make sure there is enough master volume coming from the main output.
