Johnplum

When I put my pod x3 into the front end of an amp, it's fine at first , then after a while it starts to give out a crackle, which is intermittent, but can be quite loud while its doing it. I know the pod is causing the issue because - unplugging the guitar has no effect -I've changed all the cables - I've tried it with another amp, still the same - there's no other electrical equipment on anywhere near to cause interference, and I've even tried it at someone else's house still the same Has anyone experienced anything similar? John