No, you won't damage anything by turing the preamp all the way... it just won't be as clean as it can be. You're not really sending power to the mic (although, being a condenser mic, it DOES want the phantom power on to, work, so I assume you've turned that on and know that you should NEVER plug in or unplug a mic with the phantom power on... it can destroy the mic if you pug it in at just the wrong millisecond). What you're doing is amplifying the signal coming FROM the mic. If you want more level and sensitivity, buy an external preamp, which is sure to provide more gain that the built ins. There are lots of good sounding pres for cheap these days.