Originally Posted by
WeirdBits
If you just use a standard pot then both your south coils will be permanently linked in parallel. This will be fine when the pot is in 'full split', as both coils are shorted to ground. But, when it's not being split, as both of the south coils are linked they will both pass into the north coil of the selected pickup. So, select 'bridge only' on the toggle and you'll have both bridge and neck south coils going into bridge north etc.
A concentric pot will allow you to split them individually, or a dual gang will split them together but still keep the signals separate.
Make sense?