Hi everyone, I have a question concerning my new Mark “V” Amp Head. Lately I’ve been hearing some really annoying hums and hisses in ch. 3 on Mark IV and Extreme modes. Does anyone know if this is normal or not? The hums and hisses and crackling noise are still there even when I roll back my guitars volume knob, unlike feedback which disappears. This happens exclusively in the 3rd ch. And in these 2 modes, with the gain set at 2 max. I did notice that by rolling the gain back off to 12 the noise disappears, dead silence (The way it should be!) Has anyone had such experiences with their “V”? I’m wondering if it could be the pre-valves 12AX7’s , but as I said the amp is new?!? So what’s the deal?!? thanks for all your help and suggestions, it’s all highly appreciated. By the way, I swapped to El34 tubes from the stock 6L6’s. Man what a difference. Seems like a tot. diff. animal. Love these Power tubes, SWEEEETTTTTT………..Rock on…