callaway said:
I believe that Gibson actually invented the mini-humbucker because they had made a ton of guitars with P-90 routes, but the P-90 fell out of fashion and they wanted to put a humbucker in there to appeal to a wider audience. So I think the mini-humbucker was actually designed to fit in the P-90 route with no problems.
Wish I could remember where I got that info...
The mini humbucker was originally, I believe, a pickup in the Epiphone line of guitars before Gibson took that company over in the late 50s.
The mini hum was used for jazzer hollow bodies, and the Johnny Smith style of suspended pickup.
This pickup eventually found it's way into the then new Firebird guitars, as the pickup offered some twang and treble to it, as opposed to the Gisbon humbucker which was more fuller sounding. By then (early 60s), the surf sound had taken off, darker, fuller sounding humbuckers were out of vogue, and the P90 was dismissed as old fashioned and too noisy (but Strats weren't!??).
By 1967/68, Gibson was getting pressured to re introduce the older style of Gibson Les Paul guitar due to that model's popularity with the likes of Clapton, Green, Richards etc. using old models that were no longer in production. Gibson re introduced a LP guitar in 1968, and went back to equipping them with P90s.
But the public was also demanding a LP guitar with humbuckers by then, as the age of hyper amplified backline and distortion plus reigned supreme.
They re designed the mini humbucker and improved it's 'output power' significantly and modified it so that it had adjustable pole pieces. Gibson then utilised what they had & modified P90 pickup covers & installed the newer mini humbuckers into them and used pre existing LP bodies. Thus was born the LP Deluxe.
The P90 mini humbucker cover can be bought from AllParts. So a P90 rout can accommodate a mini humbucker.
A mini humbucker will also fit into a standard humbucker rout, but the space around the pickup in that sized rout is the issue unless you are putting the pickup into a pickguard, ala Strat. I haven't seen any mounting rings that hold a mini humbucker snuggly AND cover up the rest of a standard humbucker rout. The chrome Firebird mounting rings for the mini humbuckers, do not cover up a standard humbucker sized rout.
I believe the P90 won't fit into a standard humbucker rout without significant modding of the rout or getting a P90 pickup squeezed into a humbucker sized cover.