When you really get down to it, a pickup is simply a magnet with a bunch of wire wrapped around it. The magnet creates its own magnetic field (obviously) and the guitar string interacts with that field, and this is translated by the coil of wire, and then some stuff happens in an amp, and then an audience gets rocked.
Ah, but it’s more complicated than that. The size and type of magnet you use in your pickup has a big influence on the sound that the pickup produces, as does the type of wire: how thick it is, how it’s insulated, how it’s wound around the bobbins, how many turns of wire. Then there are the pole pieces: different materials there can also affect the magnetic field in different ways. And adjustable pole pieces - which Gibson pioneered - can also help you to refine the magnetic field and its interaction with different strings. Is the B string a little quiet compared to the rest, especially when you’re running a clean tone? Well then, raise its pole piece a little to boost the height of the magnetic field in that section of pickup.
All of these factors influence the sound of a pickup, but one of the easiest to quantify is the magnet type. There are a few magnets that are typically used in pickups, and by knowing a little bit about them you can more easily figure out which one might work for the sound you’re going for. Let’s start with. We’ll start by looking at Alnico, an iron alloy which includes iron (of course), aluminum (Al), nickel (Ni) and cobalt (Co), as well as a little bit of copper (Cu). I guess when they were naming it they decided against Fealnicocu. The three most commonly used Alnico magnets for pickups are Alnico II, Alnico III and Alnico V, although Alnico VIII is also sometimes used. Let’s look a few of the most popular magnets, with a focus on how they apply to humbuckers.
It may be a little counterintuitive, but Alnico III is the weakest of the magnets used in pickups because it has no cobalt. But I guess it’d be confusing to just call it ‘Alni.’ It has the lowest magnetic pull, which means the strings are less influenced by the pickup’s magnetic pull, and this makes it a popular choice for neck pickups. It’s a little more ‘confident’ in its tone compared to Alnico II, although both exhibit a similar ‘softness.’ Many players like to balance an Alnico III neck pickup against an Alnico II in the bridge.
Examples: The Joe Bonamassa Signature Seymour Duncan bridge pickup in the Limited Edition Joe Bonamassa Les Paul Standard.
Alnico II is associated with the original PAF humbucker, and it’s still used today in a great number of pickups. The tone is relatively soft and clear, often described as sweet, with a slight rounding off of the more brittle treble frequencies. It can sound very musical and mellifluous with a clean tone, and rather ’singing’ with overdrive. If you’re running a hotter, more distorted tone you may find that Alnico II humbuckers tend to provide excellent note separation for complex chords.
Examples: 490R “Modern Classic” Neck Pickup, 490R “Modern Classic” Bridge Pickup, ’57 Classic, ’57 Classic Plus, Burstbucker Type 1, Burstbucker Type 2, Burstbucker Type 3, Mini Humbucker Bridge Pickup, Mini Humbucker Neck Pickup.
Alnico V pickups usually sound hotter and more ‘edgy’ than their Alnico II and III counterparts. They’re great at more aggressive tones and in situations where you need a little more ‘unity’ in your chords: notes may knit together a little more tightly when you’re chording through heavy distortion with an Alnico V pickup. It’s also a little warmer in the midrange, which makes it great for lead guitar.
Examples: Angus Young Signature Humbucker, Burstbucker Pro Bridge Pickup, Burstbucker Pro Neck Pickup.
Ceramic magnets are also used in some pickups. Their sound is usually characterized as more ‘modern,’ with a tighter low end, more ‘cut’ and higher output compared to Alnico magnets. You can usually bet that a ceramic-loaded guitar will sound pretty fat and thick, maybe with a little more bold midrange, especially in the upper mids.
Examples: 496R “Hot Ceramic” Neck Pickup, 500T “Super Ceramic” Humbucker, Dirty Fingers.
Aah, but there’s one pickup where you’ll find both Alnico V and Ceramic magnets. One pickup with a massive, powerful, heavily sustained tone which is suitable for the darkest, most devilish metal riffs known to man: the Tony Iommi Signature Humbucker. Gibson goes to extra lengths to ensure that this beast can be contained: it’s fully wax potted and epoxy’d to protect against the unwanted vibrations that can cause uncontrollable feedback.