Crackling coming from Right Speaker - Help

I recently began my journey into the world of tube amplification. I purchased a Genesis I60 on audiogon, and have been extremely pleased with the sound. I moved from a floorstander (Legacy) to a monitor (Focal 906). In the past month or so I have heard a crackling sound through the right channel periodically. It has been present with both sets of speakers. Being a bit of a novice, I am not sure if this is an issue with an aging tube, a cable issue, etc. Any help or guidance would be greatly appreciated!