Custom Shop wall of Fame.

There are so many pickups out there, I want to try them all. P90s, mini humbuckers, all flavors of Fender Single Coils (Jazzmaster, Jaguar, Strat, Tele and many more)… but few pickup designs have been so widely used, duplicated, investigated and reimagined as the humbucker. In this blog we’ve discussed how a humbucker cancels the hum – as Richard Irons explained so eloquently here and here. Richard also talked about the electrical path inside a humbucker here. I want to go a bit further and discuss what’s physically going on inside a humbucker. I’ll be concentrating my attention to regular, full-sized humbuckers, not the single coil-sized or stacked designs.
Maybe you’ve always wondered what some parts do, maybe you want to get some solid ground under your feet before attempting a magnet swap or maybe even a hybrid, or maybe you’re simply curious. In any case, I want to make this article your stepping stone.
The Basics
A humbucker basically needs three things: Two coils and one magnet. Without the second coil it wouldn’t be a humbucker and without the magnet, well, it would just be a bundle of copper wire doing nothing much. To make sure all the parts don’t float away they need to be fixed to a steady base called the baseplate. The baseplate has two functions: it holds the parts together and simultaneously providing a means to fix the pickup to the guitar. There you have it. A basic humbucker. No frills. Sure, you’ll need a spacer between the baseplate and the coils, in between which the magnet lies. And sure, we’re not done yet. Not by a long shot…
The Coils
The coil is the term used for the combination of those thousands and thousands of turns of copper wire around the bobbin. The bobbin is the thing that holds those turns of copper wire in place. A coil without copper is a bobbin. You can use practically anything as a bobbin. Polycarbonate and butyrate are kinds of plastic frequently used in pickups. The vulcanized flatwork usually reserved for single coils can be used as well but that material poses some difficulties of its own, making it a less popular choice. Seymour Duncan reserves butyrate for their PAF-style pickups, whereas polycarbonate is being used for nearly all other humbuckers. Butyrate gets that special treatment because of Seymour W. Duncan’s sense of reverence for history: PAF humbuckers were first wound on butyrate bobbins, so it makes but sense to wind PAF-style pickups here on butyrate as well. Especially since Seymour Duncan owns and still uses the same Leesona Winding Machines that were used by Gibson in Kalamazoo, Michigan for their PAF pickups in the 1950s!
At Seymour Duncan there is one more bobbin material that deserves more attention: glass-filled nylon. These bobbins are used on the Silver Zephyr Humbuckers and are extremely precise and stiff. The benefit is that since they’re so stiff there is very little bobbin flare when winding, making it possible to lay down a winding pattern with more precision than with any other material.
The Baseplate
The spine that holds everything together can be made of many material but often metal is being used. Nickel Silver (the same material that most frets are made of) is the material of choice at Seymour Duncan. It’s harder than brass, and doesn’t bleed off as much highs as brass baseplates do. For further reading on baseplates, click here.
The baseplate has at least seven holes in it but more often than not a minimum of 13: four holes for the coil screws, two holes for the adjustment screws when the pickup is mounted in a ring or pickguard, and one for the conductor wire. The other six holes are for the polepieces. Some pickups, like the Screamin’ Demon and the Full Shred have two rows of polepieces, giving the baseplate the grand total of 19 holes.
We covered the basics of a humbucker, but we’re not there yet. There are a few other ingredients that need addressing.
Technical Details
Polepieces
A humbucker without its cover clearly shows two rows of six metal inserts in each coil. These inserts are called pole pieces. Some are adjustable, some aren’t. First of all, there are five common types. The slug, which is unadjustable; the Fillister screw (the one with the slot), the Hex screw (the one with the hexagonal opening in its head), the large hex cap bolt (exclusively used on Seymour Duncan’s Invader pickups) and the hex threaded insert.
Seymour Duncan also uses two small metal bars per string in their Parallel Axis line (giving each Parallel Axis humbucker 24 polepieces) but those pickups are of such a unique design that I choose to omit them in this rundown.
The function of the pole pieces is to focus the magnetic field upwards towards the strings, so a string’s vibrations are better picked up. The reason there are so many styles is that each polepiece design offers a different tone. This works via inductance. The size of the head isn’t really that interesting; the overall weight and length of the screw is. The bigger it is, the higher the inductance, the ‘hotter’ the pickup becomes (to some extent) as well as the more loss of highs. This isn’t a bad thing, per se. Take for example the Invader. That pickup uses three ceramic magnets, which offer a lot of power as well as huge amounts of high end. By using those unique hex caps, the highs are softened, leaving you with a lot of low-end power and enough cut in the highs, thus creating the huge tonal ‘thump’ the Invader provides. If you were to use a regular set of polepieces in the Invader you’d end up with a pickup about as hot but with less power in the lows: the tonal spectrum would shift from the lower mids to the higher mids.
If you want to try it out yourself, take your favorite guitar with a humbucker in the neck position and screw out the polepieces and play through a clean amp (or with just a bit of crunch). You’ll see that your tone is much cleaner, clearer and more sparkly. Almost like a single-coil. That’s because the coil without the polepieces is ‘magnetically less active’ (i.e.: much lower inductance): the other coil becomes more audible while the coil without pole pieces starts to act like coil purely for noise cancellation. (Yes, I know there is no such thing as a magnetically active coil, but it would go way beyond the scope of this article to explain it scientifically correctly, so I’m sorry).
Also, some pickups use bars as polepieces. The Fuglybucker has a coil with a bar, as does the Dimebucker. A bar narrows some of the possibilities tonally but has the advantage that the output of your string doesn’t dip when you perform a string bend. That happens because the magnetic field is slightly lower between the pole pieces, and you you’ll notice it more with single coil pickups but some humbuckers have it too. Fortunately, most humbuckers are nowadays designed in a way that negates that problem.

The Custom, Custom Custom, and Custom 5 use the same wind, but different magnets. This makes a big difference.

Magnets
If the baseplate is the spine of the pickup, I could surely consider a magnet the heart of the pickup. The magnet seasons the tone, if you will. It’s the final component that adds its magic to the pickup, yet the easiest to replace (the polepieces can be cumbersome to change!). There are quite a few magnets to choose from, so I’ll try to list as many as possible. Simply put, there are two styles of magnets: ceramic and Alnico. Alnico is an abbreviation of Aluminium, Nickel and Cobalt. In other words, it’s an alloy. There are a few other alloys besides Alnico, like Cunife (copper, nickel, iron), but those are much rarer.
The Standard Magnets
Alnico 2 is one of the weakest magnets. But that doesn’t mean you should expect a low output from a pickup equipped with an Alnico 2 magnet. You should keep in mind that the final tone of a pickup is a combination of factors. The right combination will work wonders: the ‘natural tone’ of the magnet will work and match with the coils. The Pearly Gates is the most perfect of examples: it’s the weakest of magnets, the coils are wound to just 8.2k, but the combination gives a powerful, raunchy, dirty tone. The Alnico 2 will make a humbucker sound warmer, smoother, creamier in the low end if all things are considered equal (take for example the Custom, Custom 5 and Custom Custom: everything is the same except for the magnet: ceramic versus Alnico 5 versus Alnico 2). By having the coils match the ‘natural tone’ of the magnet, the pickup manufacturer can make a final result that’s bigger than the sum of its parts. This is, again, a reason why not to rely solely on DC resistance as a measure of output.
Alnico 5 is perhaps the most common magnet found in modern pickups. Compared to the Alnico 2, the A5 is more powerful and has less mids but a stronger low end and much, much more cut in the high end. If we take a look at the Custom 5 versus the Custom Custom, we notice that the Custom 5 is indeed more powerful, with more ‘bark’ in the midrange and cuts a lot better. But to show that the magnet isn’t almighty in the overall assembly of the tone of a pickup, we just have to look at the JB. The JB is notorious for its huge midrange. It goes to show that the magnet works in conjunction with the ‘tone’ of a coil.
Ceramic magnets are the most powerful of all magnets commonly used in pickups. They offer a lot of everything: lots of highs, lots of mids, lots of lows, lots of power. Ceramic magnets are made differently than Alnico magnets. The difference between an Alnico and ceramic magnet is that a ceramic magnet sintered, not forged. That makes ceramics much more brittle than Alnico.  This tradeoff gives the ceramic its power as well. Ceramic magnets come in various sizes, too. The Custom, for example, has a regular sized ceramic magnet whereas the SH-6 Distortion uses a double-thick ceramic. Yet, the Black Winter and Invader use three ceramic magnets: one double-thick magnet in the middle and two smaller yet similarly thick magnets on the sides of the pickup.
The Speciality Magnets
Alnico 3 is somewhat a more specialized magnet. It is tonally similar to Alnico 2, but with a low end that’s slightly tighter and a clearer treble detail. Making this magnet isn’t easy and the tone the Alnico 3 offers can sometimes be achieved via other means. Sometimes the unique characteristics and tonal structure of the Alnico 3 magnet can’t be duplicated via coil geometry. For example, the Joe Bonamassa Signature Set uses the Alnico 3 magnet in the bridge pickup: the clarity, sparkle and structure of the A3 simply cannot be duplicated within the tonal confines of the Bonamassa pickup. I find that it’s a great swap for other Alnico 2 pickups that are in need of a bit more sparkle, tightness in the low end and a slight boost in output.
Alnico 4 is another great magnet that’s relatively underused. Where most if not all magnets add a unique flavor to the mix, the Alnico 4 seems to offer the most clear, clean tone possible. That effect may give it the impression that a pickup with an Alnico 4 has a lower output than if it were to have any other magnet since there is much less of a frequency boost associated with the Alnico 4 but then again, that may be just what you are looking for.
Unoriented Alnico 5 was an incredibly popular magnet a couple of years ago but its popularity seems to have slowed down a bit. The Unoriented Alnico 5 is slightly weaker than its full powered, polished sibling. The regular Alnico 5 has a slight scoop in the mids and its highs are quite sharp. Compared to the regular version, the Unoriented version has softer highs and a boost in the midrange making it very useful if you want to keep the Alnico 5 characteristic but give it the impression that the magnet has undergone some intense aging over the course of, oh, let’s say, 30-odd years.
Alnico 8 is on a rise these last few years! It’s way more powerful than the Alnico 5 but not as overly so as ceramics. Seymour Duncan launched the Alternative 8 a couple of years ago as their first production pickup featuring the Alnico 8 magnet and that pickup is a true testament of the power of the Alnico 8. If you were to swap a magnet for the Alnico 8, expect a huge boost in power. The mids gain articulation and crunch, and the highs become more pronounced but aren’t harsh and the lows are huge and tight. Not all pickups can readily accept the Alnico 8, but if you get the right pickup (I’m thinking the Full Shred, JB or Custom) you’re in for a treat.

30 types of magnet wire for every tone

Wire
The final component of a pickup is the wire, as explained here from Seymour Duncan’s Vice President of Engineering. The basic material is copper. The wire is stretched out to an incredibly tiny width, approximately the width of a human hair. The width is measured in a term you may have heard, AWG. AWG stands for American Wire Gauge and works as a fraction of the base thickness. That means that a higher number means a thinner gauge. In humbuckers there are three wire gauges most often used – 42, 43 and 44 AWG – but the Custom Shop has gauges from 45 to 20. The benefit of a thinner wire is that you can put more copper wire on a coil thus getting a higher voltage. Imagine it as being a finite amount of water and several pipes through which the water has to be pumped through. The skinnier the tube, the higher the pressure. That way you can imagine a wire and the voltage running through it. The thinner the wire (i.e.: the higher the resistance) the higher the voltage, the higher the final power of the pickup. The treacherous part, though, is that the final voltage depends not only on the thickness of the wire but also the length of the wire. You can imagine that a thin wire has to be a lot shorter to get the same resistance as a thicker gauge. That’s exactly where the problem lies in trying to ascertain the power of a humbucker by reading the DC Resistance. That cold number doesn’t factor in the wire gauge and consequently the length of the wire as well as other details like the magnet, insulation, etc.

A special mention should be made of silver. The unique Zephyr Silver pickups by Seymour Duncan use silver wire instead of copper. Because silver is a better conductor than copper, one only has to imagine the added tonal benefits of silver as a coil material. Also, silver is a bit more pliable than copper, which allows for a more complex winding pattern and coil geometry, if so desired. Unfortunately the astronomical costs of silver wire of a gauge thin enough for a pickup make it unsuited for those on a tight budget.
A note has to be made concerning insulation. The copper wire needs to be insulated otherwise you don’t get tiny layers of copper wire over each other but one huge, thick turn of copper! Some oft-used types of insulation are plain enamel (PAF type pickups use this a lot), polyester, heavy poly and some others (in single coils). The difference in insulation allows for a difference in distance between the strands of copper themselves. That allows for a difference in the distributed capacitance (which I briefly discussed earlier) and that changes the overall tone and feel of the final pickup as well.
I’m always amazed how alternating a few basic ingredients can change the recipe of the humbucker so much, as to allow for an almost unlimited supply of pickups and consequently tones. I hope I’ve given you some insight in the inner technical workings of a humbucker and how each component does what to the final tone.