the EP booster warms up any guitar signal. It turns even an average amplifier into a warm, vintage sounding tone. It adds a bit of "natural" sounding compression...i love it.. I have two. With the internal dip switches you can modify the sound to fit your personal set up. I have one set a little darker than the other..and use one in front and one behind my AC Booster...the possibilities are many...and most important, musical..