Re: who here uses the mxr microamp???
I love my micro-amp. One note of caution with these is that they can vary in tone from unit to unit. I wouldn't call it entirely transparent. I'd say mine adds a touch of fat and treble in a good way. Just a touch - barely enough to notice, especially through processing.
I think it adds about 25 db. It will pimp slap the front end of your amp. It is intended as a simple clean boost. I use mine in a couple of ways:
#1 As a line booster when I'm using a lot of cord/pedals
#2 Usully, straight up solo boost - which is why the additional fat/treble is ok with me
#3 To slap my pro jr. pre-tube into next week! That can't be healthy.