That was my issue. I was playing in a very loud thrash band at the time and to get the volume needed I was pushing the amp into distortion, and the only way to avoid farting was to cut the low end - instant Lemmy but not right for the band at the time.
I often wonder if I was doing something wrong as I was playing through two custom Matamp 4x12s and still found the whole thing underpowered. Still, the guitar player I sold it to loved it.