I notice a small potentiometer in the back battery/electronics compartment of my Epic.
 
Anyone know what this adjusts?
 
Thanks to all, Bruce

It controls the output level of the buit-in preamp. So if you have other instruments, you can match the output of the Epic to the others, and use the same volume settings for your rig.
 
You can also raise or lower the pickups to where you like the sound the best, and adjust the level to compensate.
 
Happy tone hunting!