Less gain is a byproduct of less volume. I've only encountered this at relatively low volumes, however. Lowering your volume from 7 to 6 with a 100 watt amp probably won't affect the distortion.
By lowring the input to the amplifier (lowering your volume) you are driving the pre-amp less, hence less gain yes.
Quote by Lukeisonfire
tool and opeth definitly dont play tube amps . You cant get those distorted sounds out of it. tube is for like beatles stuff right?

Quote by evilbeaver22
You're right, just about the only thing better than a Spider 3 is an MG : )