I have an Ernie Ball VP Jr with the passive pot but I installed a mod purchased from a guy on eBay that buffers the tuner output, as the stock circuitry severely loads your signal when you plug a tuner in (my more tech knowledgable friend said even with a buffer in your chain before or after the vp jr)
It comes right at the end of my chain before delay & amp. Aside from the obvious swell effects and faux-pedal steel sound, I use it as a "master volume" for my +6db compressed signal before it. Even though my guitar's volume pot can achieve similar volume adjustments on a direct-to-amp rig (backline at gigs), I really don't feel comfortable playing live without a volume pedal anymore.
heres the mod / buffer I speak of http://www.ebay.com/itm/321798133459?_t ... EBIDX%3AIT