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What Are the Parts of a Guitar Pickup and How do they Affect the Tone?



Part 2: As mentioned previously, a pickup is basically a coil of wire and a magnet. But it’s quite a bit more. Let’s talk about the components. First, the Coil… 

The coil is pretty much what it sounds like: a length of hair-thin copper wire wrapped thousands of times around a bobbin.

For humbucker pickups, the bobbin is usually constructed of a plastic material like polycarbonate, butyrate, nylon or styrene using an injection mold process. For Fender-type single coils, it’s often fabricated from two pieces of vulcanized fiber (sometimes called “Forbon”) and held together with six pole pieces. However, many single pickups also use molded plastic bobbins and one, the vintage lipstick tube pickup used on old Danelectros and Silvertones, has no bobbin, with the magnet wire wrapped directly onto the magnet. Weird, I know. 

Bobbins come in various shapes and sizes. Generally speaking, bobbins that are tall and thin, like what’s found on a Stratocaster, for example, will produce more brightness. Bobbins that are flat and wide, like a Jazzmaster or P-90, will produce a fatter tone.

The way the magnet wire gets wrapped around the bobbin is usually with a winding machine. Most of the old winding machines were originally designed for wrapping transformers and were adapted to guitar pickups. Nowadays, pickup winding machines use digital counters with automatic shut-offs so they can wind a precise number of turns or wraps on a bobbin. Back in the day, pickups were wound by time rather than a precise number of turns. If a pickup winder wasn’t paying strict attention to the time, they could inadvertently wind 100 turns plus or minus on a coil—enough for a human ear to discern. That’s why there was a lot of variability in old vintage pickups with some coming out “hotter” or “glassier” or “punchier.” 

You may have heard of hand-wound pickups. If you picture some poor soul wrapping wire around a bobbin like they’re wrapping a ball of yarn, you’re probably not alone. But that’s not what’s going on with hand-wound pickups. Pretty much all modern pickups are wound on machines, most of which control the number of turns, the tension of the wire, the speed of the wrapping process and the traverse—which is the number of wraps per layer on the bobbin. With hand-wound pickups, this last process, the traverse, is controlled by hand: either with the coil wire running between the thumb and forefinger of the operator, or by using a manual traverse controller. There is a lot of lore and mystery surrounding hand-wound pickups. While they’re not as consistent as those wound with a machine-controlled traverse, each is unique and they have the DNA of the winder on them—which may or may not allow you to play exactly like Julian Lage next time you plug in.

Speaking of winding machines, there’s a fair amount of lore and mystery surrounding them as well.

And, mea culpa, I feel like I’m responsible for contributing to that hype. Some pickup makers insist that if you want to make a vintage-sounding pickup, you need to wind it on a real, ancient, vintage winding machine. (Those claims are generally made by the pickup companies who got their hands on one of the old winding machines). Others say that’s a bunch of marketing hype. (Those are the pickup companies who use modern, computer controlled machines). Be that as it may, there are plenty of folks who’ll shell out big bucks for pickups wound on old machines or hand-wound by well noted winders. And who cares, really? If you stopped snorting Cocaine in the 80s and now you’re swimming in cash, spending it on boutique pickups is probably not the worst thing you could be doing, right?

Getting back to the coil, the copper wire comes in various gauges, demarked by an AWG (“American Wire Gauge”) number that refers to the diameter of the wire. The most common AWG gauge for pickups is 42, but various others are used to achieve certain tones. The higher the AWG number, the thinner the wire. As thin as that copper wire is, it has to be insulated to prevent copper from touching copper in the coil. There are various types of insulation as well. The earliest Gibson and Fender creations used an insulation called plain enamel. Fender eventually switched over to Formvar. And there are other types of insulation as well. It’s tricky to quantify how the insulation affects the sound of a pickup, but suffice to say, if you’re buying a late-50s Gibson reproduction pickup, you might expect to see the dark chocolate hues of plain enamel insulation, or for a vintage Strat pickup, the bright gold of Formar.

By the way, some unscrupulous wire companies have sold dark chocolate brown-colored wire as plain enamel insulation—and it wasn’t. The easiest way to tell if it’s real plain enamel is to see if a soldering iron, at standard soldering heat, melts the insulation. If it does, it ain’t plain enamel. Sorry unscrupulous wire companies, you’ve been exposed.

For years, players have tried to objectively quantify the sound of pickups like horsepower or MPG with a car.

It’s a tough process; but one thing that’s easy to quantify is the DC resistance of the pickup. This metric, which is tied to the pickup’s resonant peak frequency, focuses on the coil.

Resistance to DC current is measured in ohms. Generally speaking, more turns of wire on a bobbin, or a bobbin wound with thinner wire, will result in higher DC resistance. Resistance to AC current is called impedance and impedance is measured by frequency. If you look at the frequency curve of a pickup, the frequency where the pickup’s impedance reaches its highest amplitude is the resonant peak of that pickup. Pickups with resonant peaks in the higher frequencies will be brighter with clearer upper mid-range and more present treble frequencies. Pickups with lower resonant peaks will have a beefier sound with more lower-mids and mids. 

Before I go further, I have to say there is far too much emphasis placed on DC resistance.

Part of the reason is that it’s easy to measure using a standard ohm meter. Too often, players confuse DC resistance with a pickup’s output. Though they are related, they are not one and the same. It would be like saying, “How fast does that car go?” and getting an answer like, “Incredibly fast. Just check out that awesome rear spoiler!” An awesome rear spoiler can contribute to a car’s top speed, but it’s just one of many factors. Also, when you are comparing the DC resistances between pickups, it has to be done between similar types of pickups: like two single coil Strat pickups, for example. Comparing the DC resistance between a Strat pickup and a humbucker is like comparing a Formula 1 race car to a twin-engine Cessna solely based on top speed. Both are vehicles that get you from point A to B, but they are fundamentally different beasts. 

That said, there is a direct and inverse relationship between DC resistance and resonant peak frequency. Generally speaking, a pickup with low DC resistance will have a high resonant peak frequency. And vice versa. That’s one of the reasons pickups with low DC resistance sound clearer with more presence; and pickups with high DC resistance sound beefier with more prominent mid-range. Understand this basic concept and you’ll hold your own with any gear nerd out there.

The Magnet

Let’s put the coil aside for a moment and concentrate on the other part of the pickup that has a profound influence on its tone. As mentioned earlier, the magnet creates a flux field around the vibrating strings which induces the current. Different types and shapes of magnets will create flux fields with different properties, which will result in different tones coming out of the amp.

Most magnets come in two basic shapes: bars and rods. Traditional humbucker pickups have a bar magnet that sits between two coils. With traditional single coil pickups, the pole pieces themselves are magnets. A less costly production method for single coils is to use a bar magnet coupled to steel pole pieces.

The most common types of magnets are alnico and ceramic.

Alnico (sometimes written AlNiCo) is an alloy that includes aluminum, nickel and cobalt, in addition to ferrous iron. It comes in various grades that reflect the specific blend of aluminum, nickel and cobalt with alnico 2 and alnico 5 being the most common. Alnico 2 has more cobalt in the mix. There are other alnico grades that are occasionally used such as alnico 4, alnico 6, and alnico 8. Alnico is farily easy to magnetize, but it’s prone to losing its magnetism over time, especially if it’s exposed to certain environmental factors such as shock, extreme temperature changes, or interaction with other magnets. This is one of the reasons well-played pickups with alnico magnets can lose their magnetism over time and sound different. Some pickup makers intentionally manipulate the amount of magnetism used in alnico magnets to achieve certain tones. But most of the big pickups factories just use fully-charged alnico.

The other type of magnet often used in pickup manufacture is ceramic. Ceramic magnets are made by forming a clay-like blend of ferrous material into bars using a process called sintering. While alnico magnets can hold any amount of charge between 0% and 100%, ceramic magnets are either 0% or 100% with no variability in between. They’re harder to magnetize, but they’re far more stable than alnico. There are other types of magnets occasionally used in pickup manufacture such as neodymium iron boron, samarium cobalt, and cunife, but they are seldom used and often hard to pronounce. 

Generally speaking, alnico magnets will give a warmer, sweeter, softer tone, which is why they are often—though not always—paired with low DC resistance/high-resonant peak coils and used by players who are seeking a medium output, vintage tone. Ceramic yields a brighter, punchier, more “in your face” tone, which is why it’s often paired with high DC-resistance/low-resonant peak coils; and is often favored by metal players who want power and distortion.

Next Section: Understanding the Types of Pickups

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