Hi - i bought an Ag OBP-3 off a friend, and it came with the pre, bass/mid/treb/ pots and mid mini switch, but No blend/pan or vol pot i've been told i need to add a dual 250k log pan ( blend ? ) pot and a 250k log vol pot. 1st - why does the pan/blend need to be dual ? surely a single will do ? Doesnt the knob just move the sound from one pup to the other ? 2nd - 250k/250k log pots are hard to find - only seen "mini " pots. 3rd - wouldn't it be better to have a single pan/blend, but dual vol instead ? 4th - are pan pots and vol pots the same item, values wise ?