Re: Magnet swaps for my Seths?
The Seths are one of the very best p'ups to use as a mag swap platform, as it sounds great with any Alnico magnet there is, depending on the desired tonal task ahead.
So, just go for it. Just remember to let enough time for the new magnetic field to rightfully shape before trying other magnet. This "settling-in" time varies from a just couple of days sharp for an A8 mag to at least a week (I favor two weeks) to even a whole month for A3s.
Another thing is be aware of, and can't stress it enough, is the importance of finding the "sweet spot", meaning the "right" distance from the p'up to the strings, and I'd like to add to find the right polepiece stagger.
This ensure the desired evenness of output between the strings, depending on the string set and the neck's radius, The stagger varies with the position each p'up is set in the guitar, being the neck p'up the greatest and the bridge one almost flat. The depicted is a real-life example of how it looks on a neck p'up, with a D'Addario EXL 116 (11-52) string set and a 12" radius Gibson neck.
/Peter