When you’re playing your guitar parts by yourself at lower volumes, you’ll probably want to turn your bass knob on your amp up to give your guitar full-bodied sound. However, when you’re playing loud, especially in a band situation, the low end of your signal will be a lot more present. At that point, juicing the bass knob may not add body so much as muddy up the low end and make things boomy and mushy.
To keep your guitar tone’s bottom end from getting indistinct at rehearsal/gigging volumes, try turning down the bass control on your amp. This will not only tighten up your sound, but also leave more room for the bass guitar and kick drum in a band environment, making for a better overall sound.