VA Booster is a non-battery powered color change for the pickups to which it is applied—approx. 4db on single coil-style pickups and split humbuckers. The boost's effect is less apparent on full-power humbucker pickups but lends a nice saturation and smoothness.
It is as if, with the flick of an unobtrusive mini-toggle switch (see photo), we rewind your pickups for a little more saturation and oomph while still retaining the same overall character—very nice.
Clicking the booster transitions the pickups to the next level—as though we put the “next hotter” set of pickups into your guitar.