Mixing magnet types in P90 pickups.

[Diamond]

I found some people on the Seymour Duncan forum who like to mix magnet types in P90 pickups. Instead of the regular two A5 magnets a standard Gibson P90 would have, these people for instance put one A5 and A8 in the bridge and one A4 and one A5 in the neck. This combination of magnet would help these people to fine tune their pickups and thereby their instruments. This sounds like a very good idea!

Then there are others who say that mixing two kinds of magnets will cause the strongest magnet to degauss the weakest magnet, resulting in weakening of tone over time. How much time this would take is not known. At least not to me, I couldn't find this info. Anyway, this, combined with the fact that none of the major pickup builders (SD, DiMarzio, BKP, Fralin, etc) mix different kinds of magnets, makes me suspect that there is at least some truth to it and I shouldn't try it. At least not in a guitar I want to play for a long time.

Does anyone here have any information regarding the subject of mixing different kinds of magnets and the possible negative effects this might have? Thanks in advance!!

[Philly Q]

It's an interesting question! 

I don't know the answers, but I do know of at least one production pickup which uses mixed magnets - the Gibson Tony Iommi has AII and ceramic magnets.  I think I also read that the Dirty Fingers uses two different types of ceramic.

[Diamond]

Okay, I did not know that! Thanks!! Does it make any difference that those are humbuckers and my guitar has P90's?

[Philly Q]

I wouldn't have thought so, although a P-90 is a single-coil it's constructed very much like a humbucker, with the screw polepieces and bar magnets.

There may (or may not) still be some truth in the "degaussing" theory, though, I have no idea.

[PhilKing]

P-90's have 2 magnets either side of the screws, so you can mix the magnets.  Typically humbuckers have one magnet which sits between the screw and slug pole pieces.  I'm guessing that they added magnets to replace the spacers (pieces of maple usually), which support the other side of the coil in normal humbuckers.  There are also 4 coil humbuckers (the L-6S had them). which have a magnet for each set of 2 coils.