I've been using my boost on with on my Shiva for playing rhythm since i got the amp several months. I didn't think that without the boost it would sound as full or better. It seems to sound tighter without it..of course the volume is a bit lowered, but not a problem with turning up the volume and/or preamp. I actually like it better this well...maybe it was intended for rhythm playing purposes... Do you usually have your boost on for just solos? I don't play solos, just some just leads here and there.