Just a minor note - those are not the pinstripe style. The pinstripe has permalloy lams distributed evenly across the iron lam stack, every ten lams or so. These are what you might call Peerless style as it is how the original Peerless did it, with the permalloy lams concentrated in the center of the stack. Sonically I could never discern a difference between the two methods, though Mike always kind of roots for the evenly distributed pinstripe config as being more logical. Either way the nickel/iron combo is a nice way to do a transformer if you want to give it some power. The nickel gives a little extra low level sensitivity and the iron is able to handle the loud signals with ease.
