Excellent pre-amp. It allows me to adjust the tone of my guitar with passive K&K Mini pick-up, to get a balanced tone, which is very handy in case you are not plugging into a guitar amp (that could otherwise do the EQ). For instance when directly plugging into a PA system, or connecting the guitar to something like the Boss RC-500 Loop Station. In the latter case, I connect the Boss to my amp (which has tone adjustments), but then I can no longer adjust the tone of different tracks and overdubs separately. So the preamp allows me to separatly adjust the acoustic guitar in case I add other instruments or voice (in 2nd track, or in overdubs).
Besides this practicality, the pre-amp provides an excellent tone, and it has a lot of options and adjustment possibilities for professional applications. It's a serious tool.