Hi TGP, Hi have an old 1984 Mesaboogie .50 Caliber Plus. There's a little background noise at 3-4 and it doesn't come from the guitar itself, I've unplugged everything and the noise is still there. I guess this noise is normal as it's an old amp and I can live with it (Tell me if I'm wrong). Where it comes to be an issue is when I crank it up. I want to put my amp at 7-8 and lower the volume on my guitar to get that classic tube from the tune. The little overdriven clean. BUT WHEN I CRANK IT UP I hear a vacuum sound from the amp and it sucks. Really it's louder thank you can think. Is that normal or is it broken? Because like I said at 3-4 it sounds incredible, this amp delivers an incredible clean tone. ????????????