make him turn down!!
failing that, what is your current EQ? what is the other guitarists EQ?
try upping the mids and if this makes things 'too much' then find an area in the sound where the other guy's guitar isn't and fill that - I kinda know what I mean but its hard to describe, sorry loL!
I know exactly what you mean - it was the first thing I thought when I first read this thread. But then I realised I'm doing it with recorded guitar tracks... and, from my memory of being one guitar in a two guitar band, it might take a lot of diplomacy from both guitarists to end up with two live guitar sounds where both guitarists are happy with what they're hearing out of their own amps! :lol:
I'm also wondering, are we talking rehearsals or gigs here? If it's rehearsals, get him to angle his thing away from you and vice versa... worked really well for the band I was in. Neither of us could really hear ourselves properly,
but we found out we were nicely balanced anyway to other people in the room (and when we gigged).
Other than that - I tend to agree with all the "get him to turn down" comments :lol:
Hope it's sorted by now! :D