So let's start here, I'm running my 4-string bass tuned EADG into a GK700rbii, and then into a Mesa PH210. I thought I had been hearing some crackling in the past, but the crackles were so few and far between that I thought nothing of it, maybe my cable had moved in my instrument or something. Out of laziness due to moving, I have been running out of the PA we have at our practice space, while my amp stays at my apartment and cab in the space. (I have a PH112 I play out of here). I brought my amp with me to practice a couple weeks ago 'cause I missed the sound I was getting. I get everything setup and there is an excessive amount of crackling that was coming and going from the speakers. The notes I was playing were very buzzy, like some horrible overdrive. This would happen for a few moments before it switched to how it should sound normally, clean and puncy. These two sounds seem to switch back and fourth without any volume difference. I plugged into the PA to make sure my battery wasn't dieing but there was no buzzing. I tried different cables, all worked through the PA, each one alternated between buzzing and not through my rig. For the life of my rig, I've never used exaggerated EQ'ing. The most bass boost the thing got was probably moving the knob to 12:45. I've also never turned the volume on the head up to maximum either, loudest setting it has ever seen is a hot input gain stage (-14 db pad activated), nearly flat EQ (tiny bass boost), boost knob around 9 o'clock, and master at 2 or 3 o'clock. Now logic tells me that if my head puts out 280watts at 8ohms, and my cab can handle 600watts and is 8ohms, then the speakers should be able to handle what I would imagine to be roughly 75% of the volume my head is capable of. So I don't think my speakers are blown, especially since it sounds right sometimes. I ruled out cables and the battery by using our PA. At this point I'm stumped, any ideas?