Part 5: Digging Deeper


What are pole pieces?
How does the magnet type shape a pickup's sound?
How does the nature of the coil affect a pickup's sound?
What do the specs mean?
What is "potting?"
What other factors contribute to the sound of a pickup?

Hot for Strat SSL-3 [top] has individual magnets for each string, with the Antiquity P-90 "Soapbar" [bottom] has screw-topped iron rods connected to a pair of central magnets.

What are pole pieces?

Pole pieces are elements of the pickup that sit beneath the strings and shape the magnetic fields that surround them. They can be either magnetic Alnico stock or ferrous steel. Generally speaking, individual Alnico magnet pole pieces deliver bright, tight tones, while steel pole pieces sound fatter and looser. That's one of several reasons why Fender® guitars with their magnetic pole pieces tend to sound brighter than Gibson® guitars with their steel pole pieces.

Alnico pole pieces are arranged as sets of individual magnets, usually one per string (though there are two per string on many bass pickups). Meanwhile, steel pole pieces extend upward from a central bar magnet or pair of magnets.

Most humbucking pickups have steel pole pieces in the form of screws and straight rods. Most single-coil pickups have individual Alnico magnets, though there are some single-coils with steel pole pieces, such as Gibson's P-90 pickup, a single-coil model that predates the humbucker, and many Gretsch® pickups.

Other pickups feature a single metal bar instead of individual pole pieces. Some guitarists find that this "blade-style" design provides more tonal consistency when bending strings. The pickups in our Hot Rails and Cool Rails series are blade-style.

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The Hot Rails for Tele relies on powerful ceramic magnets.

How does the magnet type shape a pickup's sound?

The magnet type is a major factor in a pickup's sound. The most common magnet type is Alnico, an alloy that includes aluminum, nickel, and cobalt. (Get it? "Al-ni-co.") The most popular types of Alnico for guitar pickups are Alnico 2, known for its sweetly musical sound, and the bolder, punchier Alnico 5.

Slash prefers the sweet vintage sound of Alnico 2 magnets.

It's fair to think of Alnico 2 as "the vintage magnet." Players who like the vintage sound, but want a little more "oomph" often choose pickups with Alnico 5 magnets. For example, our Alnico Pro II uses Alnico 2 magnets, and sounds just like a vintage Fender® pickup. But when David Gilmour wanted a thicker sound from his Strat's bridge pickup, he chose our SSL-5, which employs Alnico 5 magnets (along with a wire coil specifically wound to produce a fatter sound).

You occasionally encounter other Alnico grades in guitar pickups. One example is our Alternative 8 humbucker, which uses Alnico 8 magnets for an aggressive, high-output sound.

Hotter still are ceramic magnets. These combine iron and various rare earth minerals, formed into bars under intense heat and pressure. Ceramic magnets are usually deployed in loud, aggressive pickups designed for hard rock, such as our Invader, or the Dimebucker, which we created for the late Dimebag Darrell. But ceramic pickups don't have to be loud and distorted. For example, our ceramic-magnet Cool Rail pickups can sound quite clean and tight.

Another factor is the size and shape of the magnets themselves. Larger magnets tend to provide louder, more aggressive sounds. That's the reason for the large Å'-inch magnets in our Quarter-Pound pickups for guitar and bass. Compared to a strictly vintage P-Bass pickup, the Quarter Pound for P-Bass sounds louder and deeper, with more aggressive midrange "bite."

A good pickup designer experiments constantly with all these variables, searching for the perfect formula to bring out the best in a guitar or bass.

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Most pickups contain thousands of turns of fine copper wire.

How does the nature of the coil affect a pickup's sound?

Dramatically! It's a key determinant of a pickup's tone.

The coil is simply a long strand of insulated copper wire wound thousands of times around the bobbin or coil-form. The greater the number of turns, the higher the pickup output. But too much winding results in weak treble response and a flat, un-dynamic sound. Other factors are the wire gauge (thickness) and the insulation material.

Nowadays coil-windings are extremely precise, with little variation between same-model pickups. Back in the vintage days, a pickup stood a greater chance of being "over-wound" or "under-wound." Sometimes these "mistakes" yielded great musical results. For example, our Pearly Gates model was inspired by an over-wound P.A.F. humbucker with an uncommonly raw, aggressive "growl."

A particular coil yields different results depending on the type and shape of the magnet(s). Coil and magnet have an incredibly complex interactive relationship. Much of the craft of pickup design boils to down to finding the right blend of these components. It's as much an art as a science.

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What do the specs mean?

We usually use two terms to quantify the output and tone of a pickup: D.C. resistance and resonant peak. Their values are expressed in numbers.

D.C. resistance describes the degree to which the pickup resists the flow of direct current. Generally speaking, the higher the resistance, the louder the pickup. Vintage-style pickups usually have a lower D.C. resistance value: something close to 6.5k for a single-coil and 7.6k for a humbucker. Modern high-output pickups get as hot as 15k for a single-coil and 16.5k for a humbucker.

The resonant peak is the point at which a pickup's impedance reaches its highest level. Generally speaking, the higher the resonant peak, the brighter the pickup's tone.

You don't really need to understand the underlying physics. Just remember that a higher D.C. resistance value generally means a hotter pickup, while a higher resonant peak value means a brighter one. (Or at least up to frequencies of 7kHz or so. Electric guitars simply don't generate many frequencies above that point, so a pickup with a resonant peak above 7kHz is usually perceived as having a flat, even response.)

Using these numbers, you can make reasonable comparisons between pickup models, though this method is most reliable when comparing two pickups of the same general type-for example, two single-coil pickups, as opposed to a single-coil and a humbucker.

Whether or not you understand the science, be aware that these values tell only part of the story. These specs can steer you toward possible replacement pickups, but you really need to hear a pickup to judge it properly.

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What is "potting?"

"Potting" refers to the process of dipping a pickup in wax, which prevents the components from vibrating against each other. Usually these vibrations aren't a problem, but if you play a non-potted pickup in front of a loud, high-gain amp, you may generate unwanted feedback. Not cool, Jimi Hendrix-type feedback, but a nasty, ear-piercing squeal. That's why almost all modern pickups are potted.

On the other hand, many great vintage pickups are not potted. In fact, some are extremely "microphonic"-that is, they pick up and amplify sounds transmitted through the air along with the magnetic information generated by the vibrating strings. You can even talk into some old pickups and hear your voice through your amp.

And that's not necessarily a bad thing. A slightly microphonic non-potted pickup can have an attractive "honk," a sound many players love. We make several non-potted pickups. Two popular examples are the Seth Lover humbucker and the Antiquity humbucker, both faithful replicas of a vintage P.A.F. They're great-sounding pickups, and an excellent choice if you like vintage-style tones and play through a vintage-style amp. But they're probably not the wisest way to go if you perform in front of a wall of maxed-out Marshall stacks.

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What other factors contribute to the sound of a pickup?

Seymour Duncan volume pots come in both 250k and 500k values.

The sound you get from a pickup is partially determined by components that lie outside the pickup. These include your guitar's volume knob. The technical name for this part is a potentiometer, often shortened to "pot." (This is a different use of the word than when we talk about "potting" pickups.) The most common pot types are 250k and 500k, though many Gibson guitars use 300k pots. The higher-value pots provide a brighter sound. Many players prefer that extra brightness for humbuckers, but opt for warmer-sounding 250k pots for single-coils. The key point is that you can sometimes add or subtract brightness from a pickup by changing the pot.

Strings are another factor, and there's more to it than the fact that old, worn, or dirty strings sound duller and darker than new ones. The materials in a string's core and windings affect the way the vibrating string interacts with flux field generated by the pickup. Until a few decades ago, most

Modern strings usually sound brighter and louder than vintage ones.

strings consisted of nickel wrapped around a steel core. But nickel became prohibitively expensive, and manufacturers substituted other materials.

Most modern strings are louder and brighter than old-school nickel-wrapped ones, and most players are perfectly happy with them. But if you want a slightly warmer, softer sound from your pickups, try seeking out vintage-style pure nickel strings.

And of course, the structure and materials of your guitar are incredibly important. Some woods, such as maple and ash, are known for thier brightness. Mahogany and rosewood tend to sound darker. A guitar with a bolt-on neck usually sounds righter and "snappier" than one with the neck set into the body, though a set-neck guitar tends to provide greater sustain.

As you've learned, guitar and bass tone are the result of many subtle and interactive factors. It can get complicated! But one great thing about pickups is the way they can adjust the sound of guitar, much like a chef might fine-tune a recipe. Read on to learn how to determine which pickups will help you conjure your ideal tone from your guitar or bass.

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