The Mules are potted, unless you order them unpotted. Never had any microphonic problems or squeals with my BKP's. They handle gain very well. I have potted Mules and they're as close as you can get to a 59 PAF-tone, but they are versatile and cover a lot of ground. They're are articulate, touchsensitive, clean up great and handle loads of gain well. Global moderator Nolly uses them even for metal. I don't have experience with the out of phase wiring.