Aguilar OBP-3 for sale - at the moment it's wired up to 4 pots - stacked bass/treble, mid, blend and volume with a mini-switch for mid freq selection, but can be easily connected to whatever number of pots/holes you have by switching in/out stacked pots. I used to leave the mini switch within the control cavity as I found it very useful as a 'set and forget' option rather than something I wanted to switch mid gig.   Currently wired up with all the pots and the switch plus two battery c