You can easily turn off (Bypass) the cabinets. In any patch, just hit Edit, scroll to the cab, tap over a page and turn on the Bypass.

You'll also have to turn ON the effects loop when using the Epsi and set the input and output levels. Singtall recommends 9 O Clock input and 3 O clock for the output. Which is just about perfect for most any patch.

IMHO, it makes a really big difference in tone. Also adds something to the feel as well. Worth every penny in my book to use the Epsi.