The Evolution of Gibson Pickups: The P-90 & The PAF
Seth Lover at the Gibson Lab, Kalamazoo, 1958.
The Evolution of Gibson's Early Pickup Designs
In the mid-'30s, Gibson set out to create a pickup that would allow the electric guitar to be heard more clearly and effectively in larger ensembles. The Charlie Christian pickup, introduced with the ES-150 in 1936, was a large, single-coil design that significantly increased the electric guitar’s volume and presence, allowing it to compete with louder instruments in big bands. At the time, electric guitar technology was still in its infancy, and pickup design was an emerging and experimental field.
Gibson’s engineers, led by Walt Fuller, introduced cobalt-based magnets in this pickup, marking one of the earliest uses of this material in electric guitar pickups. This was a key distinction from the later adoption of Alnico magnets, which would become more common in subsequent models. The Charlie Christian pickup used 38 AWG wire, and was notably large, weighing approximately 1.5 pounds. Its two large cobalt magnets were hidden inside the guitar, making it both an impressive technological advancement and a physical innovation in the design of pickups. While this pickup represented a significant leap in electric guitar technology, it also marked the beginning of a long process of refinement and experimentation that ultimately led to the creation of the P-90, which would become a hallmark of Gibson’s pickup designs.
As Gibson’s pickup designs continued to evolve in the early '40s, they introduced a distinctive diagonally mounted pickup in 1940, which spanned from the neck to the bridge of the guitar. This was an innovative design that provided a unique tonal response. In 1941, this pickup was refined and shortened, with the new version often referred to as the "Short Slant" pickup. This model featured two Alnico bar magnets, a steel keeper bar for magnetic stability, adjustable pole screws for tonal customization, and a rounded plastic cover that contributed to both its aesthetic and practical design. These improvements greatly enhanced the tonal quality and versatility of the pickup, allowing for a more dynamic range of sounds suited to the evolving needs of guitarists at the time.
In 1940, Walt Fuller also finalized the development of the P-13 pickup, a more compact design that featured Alnico magnets. The P-13 was enclosed in a rectangular metal cover and included height-adjustment screws, except for the budget version, the P-13 MESG (Mastertone Electric Spanish Guitar), which lacked the adjustable pole screws found in the standard P-13. The P-13 was used on various Gibson models, including the ES-100, ES-125, ES-150, as well as lap steels. Known for its clear and balanced tonal quality, the P-13 was well-regarded by musicians and continued to be used by other manufacturers, such as Silvertone and Harmony, even after Gibson discontinued it in 1955.
Due to the constraints of wartime metal shortages and the factory’s shift to producing military supplies—such as airplane skids and submachine gun parts—Gibson’s electric pickup development stalled until the war ended in the mid-'40s. This period of interrupted production delayed the further advancement of electric guitar pickups, but it set the stage for the post-war era of increased innovation in guitar design.
The P-90: A Revolutionary Pickup and Its Variants
1946 marked the culmination of earlier developments with the introduction of the P-90, a revolutionary pickup design that would become an industry benchmark. Walt Fuller synthesized elements from previous designs to create a pickup capable of delivering a dynamic, rich, and versatile tone.
The P-90 featured a machine-wound coil made of 42 AWG Plain Enamel wire, wound onto a black styrene plastic bobbin. Beneath the coil sat two 2 1/2 inch sandcast Alnico bar magnets, with their south poles facing inward. Adjustable polepieces passed through a steel keeper bar placed between the magnets, and all components were mounted on a zinc-plated brass baseplate. The pickup was concealed under a plastic (butyrate) cover.
The result was a pickup that offered a balanced tonal spectrum with a pronounced midrange growl that quickly became its defining characteristic. This distinctive sound proved ideal for genres like jazz, blues, and rock, where the P-90’s ability to articulate both high-end bite and low-end warmth made it a versatile choice for musicians seeking a unique voice. The P-90’s powerful, full-bodied tone and aggressive midrange set it apart from its predecessors, cementing its place as one of the most iconic and enduring designs in electric guitar history.
The use of Alnico magnets in the P-90 has been a subject of interest among vintage guitar enthusiasts. Early P-90s used Alnico 3 magnets ground flat only on the south side, leaving the other surfaces rough from sand casting. This worked since the north side didn't contact any part of the pickup. However, with the introduction of PAFs, the north side needed to make flush contact with the slugs in the second coil. Soon after, new magnet types with both faces ground flat were used in humbuckers, while P-90s continued using the original Alnico 3 magnets until the late '50s. Later models blended Alnico types, with Alnico 5 becoming widespread. Each magnet type influenced the tone: Alnico 2, for example, provided a smoother sound, while Alnico 5 delivered a stronger output and a brighter tone.
By the early '60s, Gibson standardized the use of Alnico 5 magnets, resulting in a tonal character emphasizing greater clarity and power. This shift helped the P-90 remain relevant even as the humbucker began to dominate the market. Since a P-90 uses two magnet bars, it generally has higher inductance compared to an humbucker, resulting in a lower resonant peak that contributes to its characteristic warmer, midrange-heavy tone.
As Gibson's lineup expanded, so did the variants of the P-90 pickup, each designed to accommodate various guitar configurations. The Dog-Ear, Soapbar, and Staple P-90s became the most recognizable versions, each offering its own distinctive mounting system and tonal characteristics.
The Dog-Ear P-90 was commonly found on hollow-body guitars like the ES-125 and ES-330, as well as on solid-body models like the Les Paul Junior. It featured an extended plastic cover and baseplate flanges with mounting screw holes on either end, allowing for secure attachment to the guitar body.
The Soapbar P-90, used on models like the Les Paul Goldtop, Custom, and Special, featured a unique mounting system. Instead of being mounted on a pickup ring, the P-90 was directly screwed into the guitar body, with screws positioned between the polepieces. The wire passed through a protective grommet, with the hookup lead connections and ground lug located on the underside of the baseplate. Height adjustment was achieved using either springs or shims, contributing to the pickup's more streamlined, traditional design.
The Staple P-90, used primarily in pre-1957 Les Paul Customs and jazz guitars, sought to emulate the tone of DeArmond's Dynasonic pickups. Created by Seth Lover, this version employed rectangular permanent magnets and individual polepiece height adjustment screws. Though less widely used than the Dog-Ear or Soapbar variants, the Staple P-90 holds an important place in the history of Gibson’s pickup evolution.
Like the PAF, the Soapbar P-90 saw changes from the early '60s onward. The magnets were shortened, and the magnet wire switched to poly-coated versions. By the mid-'60s, wooden shims were introduced under the magnets. Then, starting in 1969, the bobbins became transparent, a feature that remained until the '80s.
The Timeless Legacy of the P-90 Pickup
Since its introduction in 1946, the P-90 has become a signature of Gibson’s electric guitar lineup. Featured on models like the Les Paul Junior, its bold and articulate sound became synonymous with jazz, blues, and rock. The P-90’s ability to produce a broad tonal spectrum—from warm, rounded bass to sharp, cutting treble—made it an ideal choice for musicians seeking versatility and dynamic expression.
Though the introduction of the PAF humbucker in 1957 led to the P-90’s diminished prominence, it never disappeared entirely. It remained in production on various Gibson models and continued to be favored by musicians who appreciated its distinctive, raw sound. In recent years, the P-90 has experienced a resurgence in popularity, with players rediscovering its ability to deliver clarity, warmth, and aggression in equal measure. This versatility allows it to shine across various genres, from the smoothness of jazz solos to the gritty, punchy riffs of rock, and even the soulful expressions in blues.
Today, the P-90 is celebrated as a timeless pickup, embodying the innovative spirit that began in the late '30s. Its legacy is a testament to the vision of engineers like Walt Fuller, whose design continues to inspire guitarists worldwide, ensuring the P-90’s place in the pantheon of classic electric guitar pickups.
Gibson’s Battle Against Hum
Like its competitor, the Fender single-coil pickup, the P-90 was affected by the interference of 50 or 60-cycle hum, caused by alternating current in electric lines. The intrusion of electromagnetic interference further exacerbated this issue, becoming a well-known frustration among customers, especially professional musicians involved in concerts, TV broadcasts, and recording sessions.
In 1954, the tide began to turn when Gibson president Ted McCarty enlisted the expertise of Seth Lover, an accomplished electronics specialist working under the guidance of engineer Walt Fuller. Lover was tasked with resolving the hum issue, and after a series of experiments, he successfully crafted a prototype by 1955.
The development of the humbucking pickup was spurred by Maurice Berlin, the owner of Chicago Musical Instruments (CMI), Gibson's parent company. During weekly meetings, CMI Vice President Marc Carlucci and President Ted McCarty expressed their dissatisfaction with the noisy P-90 to Berlin. Carlucci had learned about the issue from the Chicago sales staff, while McCarty had received complaints from celebrity clients visiting Gibson's headquarters in Kalamazoo.
While it may not be entirely accurate to credit Seth Lover exclusively with the invention of the humbucker, his pivotal role in popularizing the groundbreaking design is indisputable. The idea of a hum-canceling coil had been explored as early as 1934, with Electro-Voice's V-1 microphone, inspired by an 1892 wattmeter patent. Additionally, Leo Fender experimented with noiseless pickup configurations in 1953, creating his own humbucker design for lap steel guitars, though it never made its way into his mainstream electric guitars.
However, it was Lover’s humbucker, as implemented by Gibson, that truly revolutionized the electric guitar world. His design provided a practical solution to the persistent hum issues plaguing single-coil pickups, marking a crucial milestone in the pursuit of sonic perfection. Lover's humbucker not only addressed a critical flaw but also ushered in a new era for electric guitar pickups, shaping the sound of countless musicians for decades to come.
Pioneers of Gibson’s Electric Revolution
At the heart of Gibson's remarkable journey into the world of electric guitars were two highly influential individuals: Walt Fuller and Seth Lover. Their pivotal contributions played a key role in shaping the company’s legacy. Not only were they responsible for developing groundbreaking technologies, but their innovations also forever altered the landscape of modern music.
Walt Fuller joined Gibson in May 1933, following in his father’s footsteps, who worked as a janitor at the company. Fuller quickly ascended the ranks, transitioning from the machine shop to roles such as cost estimator and timekeeper. By 1935, he had become an electrical engineer, playing a pioneering role in the development of some of Gibson's earliest electric guitars. Over the years, Fuller accumulated five patents for his groundbreaking work, and during World War II, he continued to make significant contributions, overseeing Gibson’s military electrical assembly subcontracts.
In 1941, Fuller brought Seth Lover to Gibson as an amplifier troubleshooter. At that time, department foremen were responsible for hiring staff, a practice that continued until around 1955. Born in Kalamazoo in 1910, Seth Lover’s early experiments with radio technology laid the foundation for his later achievements. After serving in the U.S. Navy during World War II, Lover returned with a wealth of knowledge in electronics. He contributed to Gibson's legacy as an amp designer, working on the GA-50 amp and an optical tremolo before briefly re-enlisting in the Navy. In 1952, Ted McCarty convinced Lover to return to Gibson with a compelling offer.
Upon his return, Lover joined a newly established electronics lab at Gibson, where he created the Staple pickup for Les Paul, contributed to the Gibson Amp series, and, most notably, introduced the revolutionary humbucker, along with its mini-humbucker variant.
Lover’s departure from Gibson in 1967, when he answered a call from his friend Dick Evans at Fender, marked the end of an era at Gibson. However, it is worth noting that Lover’s decision to leave was partly influenced by his dissatisfaction with his pay at Gibson, which he felt did not adequately reflect the significance of his work. Nevertheless, his lasting contributions to the world of pickups, particularly the humbucker, continue to shape the sonic landscape of electric guitars to this day.
Seth Lover’s background in radio technology gave him the insight needed to solve the hum issue that had long plagued electric guitars. Drawing from his experience with phase cancellation—a technique used in radio equipment—he knew that when two signals of equal strength but opposite phase are combined, they cancel each other out. While this principle had been applied in various electronics, it had never been successfully adapted to electric guitar pickups until then.
Lover’s work on the humbucker design built on previous efforts. The concept of hum-canceling pickups had been explored in the '30s, with some early attempts leading to the filing of three patents. Interestingly, the term "humbucking," which Lover later coined, did not appear in these early filings. Two of the patents proposed impractical methods involving direct current (DC) power.
Early hum-canceling designs struggled because of the noisy amplifiers of the time, which made it difficult to distinguish between different types of hum in '30s guitar and amp setups. Additionally, many pickups produced muddy tones, which Gibson sought to avoid. Lover’s expertise in radio technology proved invaluable as he adapted phase cancellation to the electric guitar. Inspired by the tone control choke in the GA-90 amp, Lover’s design successfully eliminated hum.
A humbucker uses two coils connected in series, with opposing windings and magnetic polarities. The coils are wired so that the electromagnetic hum (noise) is canceled out. Both coils pick up the noise, but due to their opposite polarity, the hum is reversed and canceled, leaving only the guitar signal, free from hum.
After experimenting with three humbucking designs, Lover ultimately prioritized efficiency for mass production. His final design preserved both high and low frequencies, ensuring reliable, consistent performance.
While Gibson’s original goal was to create a noiseless pickup that retained the widely appreciated P-90’s tone, the humbucker offered far more. It shared similarities with the P-90, but its tonal character was distinctly different. The combined coils captured vibrations over a broader area of the strings and the noise-canceling process softened some of the harsher high frequencies, resulting in a warmer, fuller sound—a sound that has since become iconic.
Seth Lover's Groundbreaking Design
The humbucker pickup, as introduced by Gibson, borrowed key attributes from its predecessor, the P-90. Both featured an identical Alnico magnet bar and approximately 10,000 turns of AWG 42 magnet wire. Early hand-wound prototypes utilized 1/4" tall coil forms made of celluloid, housing iron pole pieces, and mounted on top of a magnet bar. These pickups were encased in a plain steel cover for protection and noise shielding. Some prototypes even experimented with modified P-90 bobbins and dog-ear mounts, blending established P-90 concepts with new ideas.
Once Seth Lover completed his innovative design, he confidently walked into Ted McCarty’s office, placed the humbucker on the desk, and declared, “Here’s your humbucker!” With that, the pickup was officially named, destined to change the electric guitar landscape. Lover then crafted two additional pre-production humbuckers for installation on a test guitar.
The chosen test guitar was a solid-body Les Paul Model with a Wraparound bridge. Modifications were necessary to accommodate the humbucker's flanged baseplate. The prototype’s cellulose plastic mounting surrounds closely resembled the final production version, and a custom pickguard was cut to fit. This Gold Top prototype was assembled with additional noise-reduction features, such as cavity shielding with paint and foil, as well as a reversed middle toggle switch position—although these enhancements were not included in production models.
In Gibson’s conference room, endorser Rem Walls played the prototype through a GA-55 Ranger amp while Ted McCarty, Seth Lover, John Huis, Julius Bellson, and other specialists observed and tested it. “The guitar worked without any hum and was immediately approved for use,” McCarty later recalled. The flawless performance of the prototype earned unanimous approval, signaling the humbucker’s bright future.
One key consideration during the humbucker’s development was the absence of adjustable pole pieces in the original design. Seth Lover initially believed adjustable poles were unnecessary, thinking they added little value to the pickup. However, Gibson’s sales team and management were concerned that omitting them could be perceived as a step backward, especially since adjustable screws were already featured on the P-90. As a result, the sales team insisted on including them for better marketability.
Some prototypes featured covers engraved to simulate pole pieces, but eventually, Lover incorporated real adjustable screws, adopting the same fillister screws and keeper bar used in the P-90. These screws, however, were not part of the original patent drawings, reflecting their later inclusion in the design process.
The pickups were mounted with the screws oriented in opposite directions—neck pickup screws facing the neck and bridge pickup screws facing the bridge—according to Lover’s preferences. The inclusion of adjustable poles proved practical, allowing for fine-tuning of the pickup’s balance.
With the design finalized, Gibson initiated tooling for baseplates, covers, bobbins, and mounting rings, preparing the humbucker for mass production. The innovative pickup was now poised to revolutionize the electric guitar market.
Decades later, in 1998, vintage guitar collector Gil Hembree, driven by an intuition—or even a “vision”—advertised locally in Kalamazoo through newspapers in search of the guitar. This led him to the son of the original owner, who wasn’t a factory employee but had acquired the guitar through other means. After verifying its authenticity, Hembree purchased the remarkably well-preserved 1955 Les Paul prototype. Today, this unique guitar stands as a priceless artifact, commemorating the ingenuity that shaped the future of electric guitar pickups.
On June 22, 1955, Gibson filed a patent application (number 2.896.491) with the U.S. Patent and Trademark Office, listing Seth E. Lover as the inventor. Titled "Magnetic Pickup for Stringed Musical Instruments", the patent outlined an ingenious solution to eliminate the hum caused by nearby electrical devices interfering with amplifiers. Ted McCarty consistently ensured that his employees received credit by listing them as inventors on company patents.
The details submitted to the lawyers were based on the prototype, with illustrations showing a pickup featuring a magnet bar and two bobbins wound with magnet wire. These coils were connected in series, with perpendicular iron cylinders in direct contact with the Alnico magnet bar, polarized along its length. The description explained how the pickup effectively neutralized undesirable currents while generating an electrical impulse from the vibrating string.
In 1956, the first production model humbucker appeared in Consolette lap steel guitars. These eight-string models featured larger bobbins and several different components. Marketed as "new, powerful hum-bucking pickups that eliminate all electronic disturbances," Gibson initially hesitated to extend the humbucker to other guitar models until the patent was secured. However, after Gretsch filed for a patent on January 22, 1957, for their Filter'Tron humbucker—developed by Ray Butts for Chet Atkins—Gibson realized the urgency of moving quickly. To stay competitive, they accelerated the production and integration of the humbucker into many of their higher-end models.
By 1957, Gibson added a "Patent Applied For" decal to protect the design, which led to the famous "PAF" nickname. The patent was officially granted on July 28, 1959, though delays were likely caused by seven other related claims. Despite Ray Butts receiving confirmation on June 30, 1959—about a year and a half after his own application—the originality and significance of Seth Lover’s design remained undeniable.
Ultimately known as PU490, the humbucker made its official debut in Gibson's product catalog in 1957, marking a pivotal moment in the evolution of electric guitar pickups.
The Humble Beginnings of an Iconic Pickup
On February 17, 1957, an entry in the Gibson logbook marked a turning point in electric guitar history: the debut of the first ES-175 equipped with humbucking pickups. The notation "A-25000 H.B. starts here" signaled the start of a new era. These early humbuckers, known as "Pre-PAF," lacked the iconic "Patent Applied For" decal that would later define the model.
A distinctive feature of the early humbucker pickups was their use of stainless steel covers, which were brushed to resemble nickel plating. This approach was a solution to the difficulty of plating stainless steel directly. Gibson did experiment with painting the covers to match golden hardware, but the paint wore off too easily, making it impractical.
Seth Lover, ever the innovator, turned to his chemistry books for a solution. His research led him to discover German silver—an alloy made from copper, zinc, and nickel. Known for its low conductivity, German silver was ideal for pickup covers. It not only simplified the plating process but also preserved the high-frequency response of the pickups.
By 1957, PAF humbuckers began appearing on Les Paul Goldtop guitars, with serial numbers ranging from 7-13XX to approximately 7-38XX. In mid-1957, the "Fretless Wonder" Les Paul Custom was introduced, featuring three golden PAFs instead of the traditional P-90s. Gibson used automated winding machines for the PAF bobbins, though the process lacked precision. Operators determined the stopping point based on judgment, leading to variations in resistance. Ohm readings typically ranged from 7kΩ to over 9kΩ, although values above 8kΩ were not particularly common, except for examples made in 1959 and 1960. Additionally, the two bobbins in each pickup often exhibited different readings. At this stage, there was no distinction between bridge and neck pickups, meaning the neck pickup could have a higher reading, contrary to what we’re used to today. By the '60s, bobbin winding became more consistent as production methods improved.
The use of Alnico magnets in PAFs was somewhat random. Alnico 2, 3, 4, 5, and unoriented 5 grades were used, with Alnico 3 being rare and mostly found in P-90s and early PAFs. Magnet lengths evolved over time, with shorter magnets becoming standard by mid-1961, typically made from Alnico 5, although some still used Alnico 2.
Most PAF bobbins were black, but in 1959 and early 1960, some pickups featured white bobbins, possibly due to a shortage of black pigment. "Zebra" PAFs, which featured one black and one white bobbin, were more common than the rarer double-white PAFs. Gold-plated PAFs, although less common, were used into the mid-'60s due to slower depletion of inventory, particularly those with an inverted magnet made specifically for Varitone-equipped guitars, such as the ES-345. Though gold-plated PAFs aren’t as sought after as their nickel-plated counterparts, those with white bobbins are especially valuable. Double-white PAFs can fetch up to twice the price of black-bobbin versions, often reaching five-figure sums.
From late 1962 to 1969, the "Patent Applied For" decal was replaced with one bearing the patent number "Patent No 2.737.843," signaling the end of the PAF era. Interestingly, this patent number referred to the Les Paul trapeze tailpiece, likely a mix-up rather than a deliberate attempt to mislead competitors. By 1960, Gibson had a surplus of unused patent number decals from the discontinued ES-225 trapeze tailpieces, which they began using on some gold humbucker baseplates—and eventually, on all of them.
The same incorrect patent number continued to appear engraved on the baseplates of subsequent pickups, including the T-Tops, and remained in use until the late '80s.
The Legendary Tone of the PAF Humbucker
The tone of the PAF humbucker is nothing short of legendary—massive, rich, fat, and full, yet with a remarkable level of intricate detail. It's as though a wall of sound envelops the listener, yet an underlying openness allows every note to breathe freely. The harmonics are complex, providing a richness that makes everything—from distorted power chords to delicate arpeggios—sound layered and dense. Even in its cleanest form, the PAF’s detail feels almost unreal; every note stands on its own, with an ethereal separation between them. There’s a certain breathiness to the sound, as if it’s alive, constantly evolving and reacting to the subtlest nuances of touch.
In its purest form, the PAF humbucker achieves the perfect balance of warmth and clarity. Its fullness never compromises articulation, even at its most saturated. It’s as if you're hearing the guitar’s tone across a full spectrum—every harmonic and overtone present without being overwhelming. Punchy yet smooth, the PAF captures every subtle shift in playing dynamics, delivering both elegance and power.
The late '50s Gibson Les Pauls equipped with PAF humbuckers revolutionized the music world, leaving a lasting impact on rock, blues, and hard rock. Known for their rich, warm tone and harmonic complexity, these guitars shaped the sound of the '60s, '70s, and '80s, becoming essential to the era’s most influential guitarists. The PAF pickups were key in defining the expressive range of electric guitars, allowing everything from crisp, articulate leads to thick, powerful solos and expanding musical possibilities across genres.
One standout example is Peter Green’s 1959 Les Paul, which defined his distinctive sound on tracks like Albatross and Black Magic Woman. Green’s tone is considered one of the most expressive in rock history. The PAFs enabled him to extract a vocal-like quality from his guitar, offering a unique dynamic range, whether with a clean, mellow tone or through powerful distortion.
Duane Eddy’s twangy rockabilly sound, shaped by his 1959 Les Paul, was instrumental in defining early rock music, with tracks like Rebel Rouser showcasing deep, resonant tones that became iconic in the genre. Similarly, Eric Clapton’s iconic Beano album, recorded in 1966 with John Mayall & the Bluesbreakers, owes much of its signature tone to his 1959 Les Paul. The PAFs gave Clapton a warm, singing lead sound that laid the foundation for blues-rock and cemented his place in music history.
Duane Allman of The Allman Brothers Band also harnessed the power of PAF pickups in his 1957 and 1959 Les Pauls to shape his soulful slide guitar tone. These guitars provided a deep, rich sound that balanced power with subtlety, perfect for tracks like Statesboro Blues and Dreams. Leslie West of Mountain also relied on the thick, aggressive midrange of the PAF pickups to create his gritty sound on Mississippi Queen, a crucial element in the development of hard rock and proto-metal.
Jimmy Page, renowned for his groundbreaking work with Led Zeppelin, embraced PAF-equipped Les Pauls for much of the band's iconic sound. His 1959 Les Paul Standard, featured prominently on albums like Led Zeppelin II and III, contributed to his complex, harmonically rich tone, enhancing his riffs and solos with a dynamic quality that became synonymous with the band’s legendary style.
ZZ Top’s Billy Gibbons crafted his signature creamy overdrive and bluesy phrasing with several 1959 Les Pauls. These guitars provided sustain and clarity, helping Gibbons create distinctive solos that balanced smoothness and bite, central to albums like Tres Hombres and Eliminator. Gary Moore’s fiery solos on Still Got the Blues were shaped by his 1959 Les Pauls, where the PAFs provided the perfect blend of warmth and bite, essential to his emotional and precise playing.
Mark Knopfler, known for his intricate fingerpicking style, benefited from the clarity of PAF pickups in his 1958 and 1959 Les Pauls. These pickups highlighted his clean, precise playing, giving his tone a bright, articulate quality that became a hallmark of his sound. Tony Iommi of Black Sabbath, a pioneer of heavy metal, also used PAF pickups in his early years to craft his iconic doom metal riffs. The dark, heavy tone of the PAFs was central to his signature sound and the development of the genre.
Although Slash’s famous Appetite for Destruction guitar is equipped with Seymour Duncan humbuckers, it still nods to the classic PAF sound. Similarly, Joe Perry of Aerosmith, who used an original 1959 Les Paul with PAFs, crafted a raw yet refined tone, particularly on albums like Toys in the Attic and Rocks.
Few modern players have embraced vintage guitars and PAF humbuckers with as much passion as Joe Bonamassa. A devoted collector and historian, Bonamassa has amassed a notable collection of original 1958-1960 Les Pauls and Flying Vs. His playing, featured in albums like Blues of Desperation and Royal Tea, highlights the expressive power and tonal complexity of PAF pickups, which continue to be central to his soulful blues-rock sound.
Other vintage guitar enthusiasts and collectors, such as Kirk Hammett of Metallica—who owns Peter Green’s iconic 1959 Les Paul—and Keith Richards of The Rolling Stones, whose arsenal of vintage guitars helped shape the band’s sound, have contributed to the preservation and celebration of the PAF legacy. Joe Walsh of The Eagles, famed for gifting Jimmy Page his own 1959 Les Paul, and Jeff Beck, whose use of vintage guitars helped define his unmistakable tone, are also crucial figures in keeping the vintage tone of the PAF pickups alive.
These legendary guitarists, each with their unique style and contributions, have solidified the PAF humbucker’s place as the benchmark for tonal excellence. Whether shredding or refining their craft, these players shaped the distinctive sound of the PAF pickups, creating timeless music that continues to influence musicians across genres. The PAF humbuckers remain the gold standard for anyone seeking the rich, harmonically complex tone that defines rock, blues, and beyond.
The Evolution of Gibson Humbuckers
From 1962 to 1965, Gibson transitioned from the original PAF humbuckers to the early "Patent No." pickups. These pickups retained much of the late PAF’s sonic character while introducing subtle refinements. Around 1963, the bobbin wire shifted from the dark enamel to reddish poly-coated copper, and the lead wires were standardized to one black and one white. The slight bowing of the bobbins from wire tension, seen in earlier PAFs, was also no longer present. Most pickups still featured the signature "L"-shaped tool marks, though these gradually faded from production. Throughout this period, nickel covers remained standard, preserving both the aesthetic and tonal essence of the PAF era. During this time, some guitars left the factory with one PAF and one Patent No. pickup.
By 1965, however, Gibson began implementing more noticeable changes. Nickel covers were replaced with chrome, aligning with the rest of the newer guitars. The bobbin wire adopted a bright orange (sometimes green) coated wire, and the "L"-shaped tool marks became increasingly rare, though some can still be found as late as 1972. Output readings stabilized around 7.5kΩ, ensuring greater consistency as production shifted to the Meteor ME-301 machines, where most PAFs were wound using Leesona 102.
From 1965 to 1975, Gibson introduced the T-Top pickup, named for the small "T" molded into its bobbins—visible only after removing the cover. These bobbins where slightly thicker, but they were still made of butyrate. Although it retained the "Patent No." sticker, the T-Top marked a departure from its PAF roots. The orange bobbin wire remained, and baseplate screws were now a mix of slotted and Phillips-head. Despite their sonic differences, T-Tops became a defining sound of late '60s and '70s rock, solidifying Gibson’s humbuckers as a central force in electric guitar history. By 1978, possibly influenced by the popularity of the DiMarzio Super Distortion, Gibson introduced double-thickness ceramic magnets. However, all Gibson pickups remained unpotted until the '80s, except for the early-'70s 'Tarback' humbuckers, named for their black epoxy coating.
As original PAF-equipped guitars became rarer and more valuable, demand for their sound led to a surge in aftermarket pickups. Seymour Duncan, for example, worked with Seth Lover—the PAF’s inventor—to recreate its iconic tone, ensuring the PAF's legacy endured. At the same time, companies like DiMarzio sparked controversy by trademarking the "PAF" name and cream-colored bobbins, a move seen by some as savvy marketing and by others as a dilution of history.
For modern players seeking vintage tones, nickel-plated Patent No. pickups remain hidden gems, offering much of the depth of PAFs at a fraction of the cost. Chrome-covered Gibson pickups from the late '60s and early '70s can vary—some house the earlier, more desirable model, while others contain a T-Top. Yet for collectors and purists, nothing surpasses the original PAF, still one of the most coveted components in vintage guitar history. Late-’70s T-Tops, however, are largely inconsistent.
Starting in 1969, Mini-Humbuckers gained prominence, offering a tighter sound, particularly in models like the Les Paul Deluxe (with PAF mini-humbuckers also found on Epiphone guitars from 1960 to 1962). In the early '80s, Tim Shaw Humbuckers marked Gibson’s first serious attempt to recreate the original PAF tone, paving the way for later reissues. Since then, Gibson has introduced several key humbuckers, including the high-output Dirty Fingers and the 490R/490T, which modernized the PAF sound. The ‘57 Classic and 498T pickups offered vintage-inspired tones with Alnico 2 and 5 magnets. The Burstbucker series and Custombucker have become staples for PAF-style tones, while the MHS (Memphis Historic Spec) and T-Type pickups continue to offer vintage-inspired sounds with modern refinements. These models remain central to Gibson’s humbucker lineup.
Today’s reproduction market continues to thrive, with companies—including Gibson itself—striving to capture the elusive tone of the original PAFs, allowing players to experience that iconic sound without the need to hunt down a rare vintage piece. Additionally, boutique makers have emerged, and among the many, a handful of them have managed to get very close to the real deal.
PAF Humbucker in a 1959 Les Paul
The Molding Process and Identification of PAF Bobbins
The thermal injection molding process for PAF humbucker bobbins was carried out by Hughes Plastic Industrial, based in St. Joseph, Michigan, using three dual steel molds for bobbin production and an additional mold for M-69 mounting rings. These molds were finalized in January 1957. Each bobbin features a mold identifier and a chamber identifier, visible on the coil former, while M-69 mounting rings have their respective codes (and also the HPI logo) stamped underneath.
The first mold, CF-491-1, was used to produce screw bobbins with regular spacing. These were marked with CF-491-1 and chamber identifiers 1 and 2. The second mold, CF-490-2, was designed for slug bobbins with regular spacing, marked with CF-490-2 and chamber identifiers 3 and 4. The third mold was used for M-69 mounting rings, which produced both the short version (MR 491, marked with MR 491 and 7) and the tall version (MR 490, marked with MR 490 and 8).
The fourth mold, also labeled CF-491-1, was initially the first mold but was later refurbished to produce screw bobbins with narrow spacing. These narrow-spacing bobbins are marked CF-491-1, with 1 for the slug coil and 2 for the screw coil. The "CF" designation stands for "Coil Form," while "MR" refers to "Mounting Ring."
Vintage butyrate bobbins from this era often show tooling marks and minor imperfections, such as burrs at radius transitions, which are unique to each mold. When Gibson required an intermediate mounting ring for a three-pickup guitar, a tall MR 490 mounting ring was sanded down for use instead of the initially intended MR 493 design. An even shorter MR 492 was abandoned, which is why there are no parts numbered 5 and 6 until years later.
These small details are crucial for identifying original PAF components and understanding the production techniques of the time.
The Authenticity of M-69 Pickup Rings
M-69 pickup mounting rings, used for PAF humbuckers, are distinctive components easily identified by the mold markings on their undersides. These markings, a result of the injection molding process, indicate both the mold and model: bridge pickup rings are marked MR490, while neck pickup rings are marked MR491. Guitars originally equipped with PAFs featured either black or white M-69 rings. While black rings were more common, white rings were exclusive to Les Pauls, ES-295s, and select steel guitars, making them rare and highly sought after, often commanding unexpectedly high prices.
M-69 rings were made from Cellulose Acetate Butyrate (CAB), a thermoplastic cellulose ester known for its moderate butyryl content and low viscosity. Popular in the '50s, butyrate has since fallen out of favor. It is easily recognized by its distinctive odor, often described as sour milk or vomit-like.
To prevent cold joints during the molding process, the mold was gated. However, minor imperfections were introduced during the hand tooling of the original steel molds, leading to characteristic irregularities in the final molded parts. One notable feature is the oddly shaped screw funnel post on the bridge ring, a result of a repair made during the mold’s creation. These imperfections, along with subtle variations in texture, are key indicators of authenticity. Another distinctive characteristic is the half-moon-shaped ejector pin marks. Additionally, the rings’ signature bowed short ends are a natural consequence of the plastic’s shrinkage as it cooled.
The original M-69 rings also had a unique flexibility, allowing them to easily contour to a carved top. The pickups are secured using SAE 3-48 x 1" screws, paired with 1 5/8 inch steel springs for height adjustment. The rings themselves are fastened with partially threaded flat Phillips head screws (size #2), with two different lengths used to accommodate the tall and short rings. M-69 rings can be found on Gibson guitars up to 1969.
Between 1966 and 1967, Gibson used “generic” mounting rings due to a transition at its supplier. HPI moved to a new factory in 1966, upgrading its equipment and planning to retire old molds, including those for Gibson’s humbucker bobbins and mounting rings. As the transition progressed, HPI produced unmarked "generic" rings to bridge the gap before new M8 rings were introduced. In January 1967, a severe blizzard collapsed the roof of HPI’s new factory, delaying production for three months. This likely pushed back Gibson’s adoption of the new T-Top bobbins and M8 rings, which were finally introduced in early 1968.
Examining Butyrate Bobbins in PAF Manufacturing
The bobbins used in PAF pickups are made from Cellulose Acetate Butyrate (CAB), the same material used for M-69 mounting rings. Butyrate is a relatively soft material known for its unique resonance properties. Since these pickups do not use wax potting, the mechanical characteristics of the butyrate material subtly influence their microphonic behavior. Nonetheless, attempting to pot these pickups would be problematic, as CAB is highly sensitive to heat and prone to warping.
A few key mechanical specifications stand out. One notable detail is the slight difference in coil former sizes between slug and screw bobbins, even though they share the same outer dimensions. The nominal inner width of the bobbins is 1/4", with the E-to-E spacing measuring 1 15/16" (49.2mm), except in narrow-spaced PAFs. Another distinctive feature is the square-in-circle hole located on top and on the underside of the bobbin, through which the start lead wire passes. This design was originally required to fit the PAF bobbin into P-90 machine fixtures but was discontinued after the Patent No. era. In the non-adjustable bobbin, the hole is a larger circle with an offset square.
Butyrate bobbins typically lack a glossy finish and often show slight recesses between the poles, a result of material shrinkage during molding (CAB has a shrinkage factor of 2.5%). Due to the relatively soft nature of this material, butyrate bobbins can warp slightly under high winding tension.
Most PAF pickups were originally equipped with double black bobbins, although some feature one or both white bobbins. The use of white bobbins may have been due to a temporary shortage of black material or to fulfill orders for white mounting rings. These white-bobbin pickups first appeared in 1959, though they may have been produced earlier. Contrary to popular belief, there is no standard "zebra" or "reverse zebra" configuration, as the white bobbin can appear on either the slug or screw side.
PAFs with both white bobbins are especially valuable due to their rarity and association with iconic vintage burst players, and they have also become the subject of various legends. These pickups are not found on later PAF or Patent No. pickups, as their use was phased out after the early '60s. If a PAF retains its original cover and unaltered solder joints, the bobbin color can often be identified by inspecting them from the retaining screws.
T-Top bobbins were still made of butyrate and were exclusively black. They had thicker walls, making them stiffer. Unlike earlier bobbins, they lacked the 'square-in circle' holes. Their most recognizable feature was the molded 'T' on top, designed to ensure correct orientation and prevent incorrect installation.
Decoding the 'Vintage White' Color of Plastic Parts
While black is just black, light-colored plastics exhibit more complexity. The term "vintage white" is commonly associated with the distinctive off-white or ivory color found in vintage Gibson components, such as pickup rings and bobbins, made from Cellulose Acetate Butyrate (CAB).
Originally, CAB has a neutral, pale ivory hue. However, over time, photooxidation occurs when the material is exposed to ultraviolet (UV) light and oxygen. This chemical reaction breaks down the polymer chains in CAB, causing the plastic to gradually yellow or develop a cream-like discoloration. The rate of this process is influenced by factors such as sunlight exposure, handling, and environmental conditions, making each vintage piece unique in its aging process.
In contrast, Acrylonitrile Butadiene Styrene (ABS), the material commonly used for pickguards, ages differently. ABS undergoes oxidative degradation, leading to darkening, often taking on an amber or yellow hue over time. While modern plastics are engineered to resist these aging effects, these natural color shifts in vintage parts add their charm.
For guitar collectors and enthusiasts, the gradual transition of these components from their original color to cream or yellowed tones adds to the historical charm and character of vintage instruments. A fascinating effect of this aging process can be observed under a blacklight, where these components glow with a distinct hue, making it a useful tool for authenticating vintage parts.
The Authenticity and Function of PAF Covers
The vintage PAF humbucker pickup cover served both functional and aesthetic purposes, contributing to the classic look of these highly sought-after pickups while also enhancing their performance. Functionally, the cover shielded the coils from radio frequency interference and provided mechanical protection.
The original covers were produced by HPL Manufacturing Co., based in Cleveland, Ohio, using German nickel silver—an alloy composed of 60-65% copper for workability, 17-25% zinc for hardness, and 10-20% nickel for its silver-like appearance and corrosion resistance. The sheet stock used was initially 0.022" thick, which, after processing, measured approximately 0.021". Around 1959, Gibson transitioned to a thinner 0.020" material. The manufacturing process included deep-draw stamping, flush-cutting, belt-grinding, and wheel-polishing. These covers had a distinct shape, with flat faces, sharp side edges, rounded corners (reminiscent of old TV screens), and slightly recessed screw holes, often referred to as "dimples." Over time, the contours of these covers evolved due to die wear and variations in hand-finishing before nickel plating, with covers from the '60s displaying a softer shape.
The precise fit of the cover ensured a snug placement over the bobbins, minimizing susceptibility to feedback despite the absence of potting, resulting in only a slight increase in microphonics.
The low conductivity of nickel silver, coupled with the omission of a copper pre-plate in the electroplating process, helped preserve the pickup’s tonal characteristics. In contrast, gold-plated covers (24k gold over nickel) had a slightly greater impact on tone due to the inherent material properties of gold. In 1965, Gibson switched from nickel-plated to chrome-plated covers, aligning with a broader shift in the company’s hardware finishes. The plating process was handled by Bronson Plating in Kalamazoo.
Over the years, guitarists have debated the sonic differences between covered and uncovered PAFs. A covered, unpotted pickup introduces a subtle metallic overtone and "cluck," with the effect influenced by its proximity to the strings. Removing the cover slightly increases treble response and allows for closer pickup-to-string adjustment, enhancing perceived output and introducing a subtle thickening of the tone. Ultimately, the choice between covered and uncovered PAFs remains a matter of personal preference, balancing tonal transparency, resonance, and aesthetic considerations.
Understanding Alnico Variations in Vintage Pickups
Gibson’s PAF pickups are legendary for their unique tonal qualities, and one of the most fascinating elements behind their sound is the variation in the types of Alnico magnets used. The choice of Alnico grade, the length of the magnet, and even the inconsistencies in their production all played a crucial role in shaping the sound of these early pickups.
Alnico, an alloy of aluminum, nickel, cobalt, and iron, is well-regarded for its warmth, clarity, and smoothness. It was the most powerful permanent magnet of its time, which made it a popular choice for various applications, including electric guitar pickups. In the early days of PAF production, Gibson used a mix of Alnico grades, resulting in pickups that varied in sound. This variation contributed to the diverse tonal profiles that made each PAF unique.
Among these, Alnico 3 is notable as the weakest and rarest magnet found in vintage PAF pickups. Lacking cobalt, it produces lower output and a softer, less dynamic response, with reduced harmonic content. These characteristics made it less popular, and by 1957, it was phased out in favor of other grades.
Alnico 2, on the other hand, is cherished for its rich, smooth tones, featuring a scooped midrange and bell-like highs. It delivers a mellow, sweet sound with a softer low end, contributing to a smooth and slightly compressed feel.
Similarly, Alnico 4 offers a balanced tonal profile with a drier, more controlled response. It emphasizes the midrange while keeping treble and bass in check, making it a versatile choice.
In contrast, Alnico 5 is known for its brighter, more focused tone and increased output. It accentuates the midrange, providing excellent clarity and definition, particularly in the upper frequencies. The Alnico 5 crystals are aligned during the production process, exposing the material to a strong external magnetic field during or after casting. This alignment causes the magnetic domains to organize in a specific direction, enhancing its remanence (magnetic strength) and coercivity (resistance to demagnetization), ultimately improving the magnet’s performance. Its strong low end and pronounced highs create an aggressive, articulate sound without being harsh.
There is also an unoriented variation of Alnico 5, first identified in vintage PAF pickups from the late '50s through research by Tim Shaw at Gibson in the '80s. Shaw theorized that this variation resulted from an accidental heat treatment issue during production. Unoriented Alnico 5 retains similar magnetic strength to Alnico 2, offering comparable output but with a distinct tonal character. It produces a midrange-focused sound with a tighter low end and a sharper response, yet retains some of the smoothness of Alnico 2. This tonal difference is due to the variation in inductance profiles, giving unoriented Alnico 5 a crisper, punchier tone with a more dynamic presence.
Gibson used these magnets interchangeably, leading to natural variations in PAF tonal response. However, in 1961, the company standardized the use of shorter Alnico 5 magnets. While this transition was gradual and inconsistent—some early '60s models still featured long Alnico 5 magnets, and occasionally short Alnico 2 magnets—the change significantly influenced pickup performance.
The length of the magnets played a key role in shaping the PAF sound. Early PAFs used longer magnets, around 2 1/2 inches. However, by 1958, Gibson began using shorter magnets in some pickups. This change became more standardized in July 1961, when Gibson officially reduced the magnet length by approximately 1/8" to 1/4". The shorter magnets weakened the magnetic field, slightly lowering the pickup’s output, but the switch to Alnico 5 helped compensate for this. Generally, longer magnets produce a warmer sound, which is why late ’50s PAFs are still the most sought-after—shorter magnets became more common in later models.
An accidental occurrence in the world of PAFs is the flipped magnet bar, as seen in the famous 1959 Les Paul "Greeny". During a later repair, the magnet bar was mistakenly installed backward, reversing the pickup's polarity. This unintended modification resulted in a distinctive out-of-phase tone when both pickups are used together, making it a truly unique piece of rock history.
The Impact of Magnet Manufacturing on Tone
The magnet manufacturing process played a significant role in shaping the sound of the pickup. These magnets were rough-cast, meaning the alloy was melted at high temperatures and poured into molds made from fine sand. This method, known as sandcasting, resulted in magnets with a coarse, uneven surface. The texture of the sand, along with material irregularities from the cooling process, created small variations in the final magnet, contributing to subtle tonal roll-off.
Once the magnets were cast, they were magnetized in-house by Gibson using a method developed by Glen Seybert, an employee at the company. Initially, Gibson purchased uncharged magnets, which were more cost-effective. Seybert’s technique involved placing several magnets in a homemade magnetic charging block, creating a collective magnetic field that magnetized them all at once. While this method worked, it didn’t fully saturate the magnets with charge, leaving them weaker than magnets that had been individually magnetized. This led to some inherent inconsistencies in magnet strength, making some PAFs more powerful than others.
This magnetic marking system was a rudimentary method, which further contributed to variations in the strength and tone of the magnets. The North side of the magnets was marked with a felt-tipped pen.
Over time, Gibson sourced magnets from various suppliers, including General Electric's Carboloy plant in Edmore, Michigan, which became a significant source of Alnico magnets during the late '50s. Other suppliers included General Magnetics of Indiana and Allied Chemical, based in Chicago, Illinois. The quality of the magnets depended on both the materials and production methods, and fluctuations in sourcing sometimes led to differences in the final product.
The rough-cast, unevenly magnetized nature of these early PAF magnets gave each pickup its own character, creating the warmth, subtle complexity, and vintage charm that many players still seek today. The combination of material choice, production techniques, and natural inconsistencies are what truly set the PAF apart.
The practice of “magnet hijacking,” in which players place P-90 magnets into modern humbuckers to replicate the vintage PAF sound, has gained popularity. However, it’s essential to note that the final tone is shaped not only by the magnets but also by the winding of the coil, the placement of the magnets, and other production variables.
As PAF pickups age, many believe their sound evolves, particularly due to the magnets. While Alnico magnets can lose some strength over time, this decay is generally slow and minimal under normal conditions—only about 1-2% per century. Significant loss of magnet strength usually occurs only with exposure to extreme heat or strong magnetic fields.
The Role of Magnet Wire in Shaping the Sound
One of the defining elements of vintage Gibson PAF pickups is the use of 42 AWG (0.063mm) Plain Enamel magnet wire, also referred to as PE. This copper wire, coated with a thin layer of enamel insulation, was crucial in shaping the electrical and tonal characteristics of these iconic pickups.
This enamel insulation once common, was acetate-based and applied in a thin, uniform layer (single build). However, inconsistencies in coating thickness and even “warts” (raised imperfections) were common, leading to slight variations in wire properties. The color of the coating varied from dark orange to purplish brown. Unlike other types of magnet wire, the enamel insulation required mechanical removal before soldering, a process now replaced by solderable coatings in modern wire. While the primary purpose of the coating was to insulate the copper wire, its thickness and dielectric constant also influenced the coil's capacity, influencing the frequency response.
The copper wire was sourced from multiple suppliers, with International Wire Group (IWG) being one of the largest. The copper used then was not as refined as today's, with variations in purity and composition due to less strict manufacturing standards. The processes of drawing and annealing— where the wire is stretched and heat-treated to adjust its properties—were less controlled than today's methods, leading to subtle differences in resistance, ductility, and diameter. These variations in copper processing contributed to the unique tonal qualities of the pickups, as even slight changes in the wire’s characteristics could affect the electrical behavior.
These subtle variations in wire diameter, coating thickness, and resistance “per foot” influenced the final tonal output, contributing to the distinctive sound of vintage PAFs. In 1963, Gibson transitioned to poly-coated wire, marking a shift from the characteristics that made these early pickups so revered. This change was driven primarily by production efficiency, as poly-coated wire was easier to work with.
The Construction and Winding Process of a Vintage PAF
Gibson originally wound each PAF guitar pickup using the same wire as their P-90 pickups. A typical PAF consists of two bobbins, each wound with approximately 5,000 turns of this wire. However, the actual number of turns could vary due to inconsistencies in the winding process. Some machines lacked stop counters or had malfunctioning ones, which led to slight underwinding in some cases, while others were overwound by as much as 1,000 turns—particularly in the late '50s. As a result, the DC resistance (DCR) of vintage PAF pickups varies widely. Some pickups are notably hotter than others, and many exhibit moderate coil mismatches. A mismatch in turns—often up to a few hundred—can enhance the treble response without affecting hum cancellation. Higher DCR can also result from higher resistance per foot of wire or increased winding tension (due to greater pressure from the machine’s felt tensioners, which stretch the wire). Contrary to popular belief, most PAFs are not drastically far off their intended winding specifications.
Unlike Fender pickups from the same era, all P-90 and PAF pickups were machine-wound. An automatic transverse guide ensured even wire distribution across the bobbin, minimizing wire scattering compared to manual winding. This method also resulted in lower coil capacitance due to the reduced overlap of the windings, contributing to a brighter tone. However, the interior of a PAF’s coil often appears uneven. The start lead wire runs internally into the bobbin, winding around the plastic former and obstructing the path of the magnet wire. This interference causes the inner layers of the coil to be less compact, contributing to the enhanced microphonics characteristic of vintage PAF pickups.
The lead wire for both the start and end of each coil is a 7-strand, 28 AWG tinned copper wire with black PVC insulation. The start of the screw bobbin is soldered to the nearest corner of the baseplate, while the start of the slug bobbin is soldered to the core of the output wire. These two coil ends are then connected. In later Patent No. pickups, the coil leads were color-coded black and white, with the end wire marked white to prevent confusion with the start, as the start wire was repositioned externally and no longer passed through the bottom hole.
To protect the coils and soldering, a 1/4" black flatback paper tape is applied. A small piece of 1/2" tape (or sometimes two 1/4" pieces) covers the side with the lead wires. This tape, known as 3M’s Scotch #4 Tape, is recognizable by its black adhesive and olive-green color under blacklight. Notably, this tape is no longer in production. The solder used was the common lead-tin alloy, due to its relatively low melting point and good conductivity.
In a Gibson humbucker, both coils are wound counterclockwise when viewed from above. The coils face the opposing poles of the magnet bar, with the screw side facing the south pole. In the PAF design, the side with the lead wires is opposite the baseplate hole where the output wire exits, with the wire running along the edge.
During the Norlin years, Gibson began wiring the leads on the same side as the hole to save on braided wire length. Some pickups even used gray PVC multi-conductor wire. Another change from this period was the switch from a single maple spacer under the slug bobbin to two white plastic spacers.
The absence of paraffin potting in vintage Gibson pickups allows the coil windings to resonate naturally, enhancing harmonic content and producing a richer, more dynamic tone. This results in a unique, organic character with increased sensitivity to a player's touch. While slightly more susceptible to feedback, their solid construction helps keep it under control. Additionally, wax potting introduces capacitance, which further alters the tone.
The Machines Behind Gibson's Iconic Pickups
The creation of PAF pickups was significantly influenced by the machines used to wind their coils, a total of four: the Gibson Seybert Winder, the Geo-Stevens 115, the Leesona 102, and the Meteor ME-301. While these machines hold historical relevance, it was the winding process itself—rather than the machines' features—that played a key role in shaping the PAF's iconic tone. While many believe PAFs were hand-wound, no original PAF pickups were—except for rewinds of old coils.
The Gibson Seybert Winder is a vintage pickup-winding machine dating back to the 1930s, originally manufactured by Crown in Illinois. It was first used to manually wind large diagonal pickups, such as those found in the 1940 ES-300 guitars and possibly the Charlie Christian pickups from the same era.
In the '50s, Glen Seybert modified the machine into an auto-traverse pickup winder by adding a wooden wire guide and tension mechanism. These modifications, which included period-typical parts like cream-colored strap buttons used as wire guides, were likely made to increase the production of the newly introduced PAF pickups, allowing the machine to meet growing demand.
Powered by a separate electric motor, the winder’s unique drive system causes the winding mechanism to move unevenly, slowing down as it nears the end of its traverse. This results in a distinctive hourglass-shaped coil, setting it apart from other winding machines.
The winder was designed to wind four slug bobbins at a time, but it could not accommodate screw bobbins. Although it could have been fitted with a necessary tailstock fixture, this upgrade was never implemented.
Due to its exclusive use of slug coils, unique winding pattern, and the absence of a stop counter, PAF pickups produced on this machine tend to have a distinct tonal character. While it was eventually retired, its impact can still be heard in some vintage PAFs.
The Geo-Stevens 115 pickup winder has a notable history, first entering the Gibson factory in Kalamazoo in 1950. Built by Geo-Stevens, it was originally ordered by industrial supply company Allen Electric & Equipment. This machine played a crucial role in the production of PAF and P-90 pickups, featuring unique fixtures that limited wire traverse, resulting in a coil with more scatter and a "center-focused" design.
Although the machine achieves an optimal Turns Per Layer (TPL)—calculated by dividing the bobbin width by the wire’s outer diameter—its shorter wire travel produces a fatter coil with fewer turns of 42 AWG wire. This results in a warmer, low-end tone. A few hundred extra windings fully pack the bobbins, widening the magnetic aperture. Notably, the machine was not equipped with a stop counter.
In 1956, its motor was replaced, and it continued winding PAF and P-90 bobbins at the Kalamazoo factory. Later, as Gibson transitioned to Nashville, Les Paul himself rescued the machine, though it remained unused for decades. In 2015, it was sold at auction and later acquired by Throbak, which also owns the original Gibson Seybert Winder.
Still bearing the wear marks from winding countless PAF and P-90 bobbins, the machine remains a legendary piece of pickup history.
The Leesona 102 holds a special place in the world of PAF pickups. Known for its precision winding, this machine is highly regarded by enthusiasts. Like the Geo-Stevens machine, it produces an optimal TPL, but its unique design featuring a lobed cam allows for a more even distribution of wire, resulting in a more consistent coil shape.
Originally built by the Universal Coil Winding Company, the Leesona 102 was designed as a versatile industrial coil winder, capable of handling coils from 3” down to as small as 1/32”. Its most notable feature is its lobed cam, which enables a smoother wire traverse and a more uniform winding pattern. This precision contributes to the unique tonal signature of PAF pickups—rich and full-bodied, with a balanced low end and clear mids. Compared to the Geo-Stevens 115, the Leesona’s coils tend to be more uniform and less "scattered," resulting in a slightly more defined midrange response.
In the early '50s, Gibson began using the Leesona 102, marking a turning point in PAF production. This machine played a crucial role in creating Gibson’s iconic pickups and was also used by companies like Rowe Industries for their DeArmond pickups. Though originally built for various industrial applications, its ability to wind exceptional-sounding guitar pickups cemented its legendary status in vintage gear history.
The Leesona 102 features a three-station setup with an adjustable traverse, making it well-suited for winding different pickup models, including the PAF. It was more efficient than other machines of its time, offering smoother and faster production. However, its size and weight led to many units being discarded as scrap in the early '90s. As a result, the Leesona 102 is now extremely rare, with only a handful of operational models remaining.
While renowned for its quality, the Leesona 102 wasn’t without quirks. The adjustable traverse, though versatile, introduced slight inconsistencies in the winding process at the smaller settings. The counters were also prone to failure.
With its rich history and rarity, the Leesona 102 is more than just a tool; it’s a vital piece of the legend surrounding the iconic PAF pickups. Of the two original machines used by Gibson, both are now owned by Seymour Duncan, though only one—modernized—remains operational.
The Meteor ME-301, often regarded as the most efficient PAF pickup winder, holds a unique place in Gibson’s winding history. Unlike other PAF winding machines, the ME-301 combines low wire tension, a highly accurate traverse, and a TPL setting of 65—lower than optimal. These characteristics result in consistently wound coils that are fuller and slightly warmer in the low end compared to those wound on the Leesona 102.
A Swiss-made machine, the ME-301 was designed with production efficiency in mind. Dating back to the '50s, it is still in use today at the Gibson Pickup Shop, though modern modifications have removed its original Meteor wire guides to accommodate more bobbins per machine. Its quick-change chuck system allows operators to swap fixtures rapidly, making it well-suited for mass production.
What sets the ME-301 apart tonally is its approach to TPL adjustment. Rather than requiring manual fine-tuning, the machine features a large dial where the operator simply selects the wire gauge. For a PAF coil, turning the crank to 42 AWG wire automatically sets the TPL to what should be the most efficient setting. However, every ME-301 ever built has this setting calibrated 35% lower than optimal, creating a distinct winding pattern that defines the sound of pickups wound on this machine. If adjusted while running, the friction disc that controls the TPL will undergo excessive wear. A worn friction disc will cause a significant TPL deviation.
This unique winding characteristic makes ME-301 coils instantly recognizable in vintage pickup repairs. It was used to wind not only PAFs but also P-90s, mini-humbuckers, and later Kalamazoo-made T-Tops.
The ME-301’s combination of efficiency and distinctive winding characteristics has solidified its legacy as a key player in the production of Gibson’s legendary pickups. Even today, its impact continues to be heard in the warm, balanced tones of the guitars it still helps to shape.
The Small Parts That Shape Humbucker Tone
The smallest components of a PAF humbucker—pole screws, slugs, and the keeper bar—play a vital role in shaping the pickup’s tonal characteristics. These parts contribute to the magnetic circuit, transferring magnetism from the Alnico bar magnet to the strings. Their material composition, geometry, and manufacturing precision all influence the pickup’s response, dynamics, and harmonic complexity. Each component serves a unique function in defining the PAF’s tone. The steel grades used for the pole screws and slugs directly impact the pickup’s overall sound. Additionally, the way these parts are manufactured and assembled is crucial to preserving the legendary PAF tone.
Originally produced by Watkins Machine Shop in Kalamazoo, Michigan, the materials used in PAF pickups remained consistent throughout their production. Lab tests on vintage samples confirm that the material chemistry did not change during this period.
One of the most important small components in a PAF pickup are the pole screws. Each PAF features six slotted, 5-40, 3/4" fillister head, nickel (or gold) plated pole screws that are adjustable. These screws enable precise fine-tuning of the string response by raising or lowering them. The steel composition of these screws directly influences the treble frequencies.
Vintage pole screws typically have a lower carbon content, ranging from 1006 to 1018 steel grades. This results in a smoother, less aggressive treble response compared to modern counterparts, which generally feature higher carbon content. Additional details about these screws include a short 'cheesehead' profile with a rounded top, non-tapered threads, and an indentation at the end. Furthermore, the head cut may sometimes be slightly off-center.
In addition to the adjustable pole screws, slugs are crucial for completing the magnetic circuit. These nickel-plated steel slugs are pressed into the bobbin on the side facing the north pole of the Alnico magnet. Made from 1215 steel—a material selected for its superior machinability and ability to be cut without lubricants—slugs still require the most complex production process. The cutting process, carried out on a Brown & Sharpe machine, often left a distinctive bullseye pattern on the surface.
The specific steel composition of the slugs significantly influences the pickup’s response, helping to reinforce the balanced tone that characterizes a classic PAF. A hard maple spacer is positioned on the side opposite the magnet-facing side of the slugs, stabilizing the bobbin and ensuring its structural integrity.
Another vital component is the keeper bar, a precisely cut steel piece that is machine-flattened on both sides and drilled with ten holes to accommodate the pole screws and bobbin mounting screws. It serves two primary functions: maintaining the charge of the Alnico magnet and stabilizing the bobbin on the baseplate.
The keeper bar is made from cold-rolled 1016 steel, a material that is no longer in production. This particular grade of steel offers an excellent balance of magnetic permeability and machinability, making it an ideal choice for its role in the pickup’s magnetic circuit. The low carbon content of 1016 steel allowed it to maintain good magnetic efficiency, enabling the efficient transfer of magnetic flux between the magnet and the pole screws, which played a crucial role in optimizing the pickup’s overall performance.
Though often overlooked, these small components are critical to the PAF’s tonal characteristics. Their metallurgy, manufacturing precision, and assembly process all contribute to the distinctive sound that has made vintage PAFs highly sought after. These materials and design choices continue to uphold the legendary status of these pickups.
The Anatomy of a PAF Baseplate
The PAF baseplate is a crucial component of its legendary design, serving as both the structural foundation for the pickup assembly and a key influence on its tone. Produced by Watkins Machine Shop from 1/2-hard nickel silver alloy, the baseplate provides tonal transparency, unlike the zinc-plated brass baseplates of P-90 pickups, and readily accepts solder, ensuring a solid connection for the pickup cover. It also serves as the primary grounding point, with the braided shielded wire soldered to it.
Its threaded legs allow height adjustment screws to secure the pickup to its mounting ring, and the distinctive "L"-shaped tooling marks in the feet, left from the stamping process, help authenticate a vintage PAF. Unlike modern humbuckers, vintage PAFs feature pole screws that thread directly into the baseplate, creating a solid mechanical structure. This design enhances tonal clarity and resonance while minimizing feedback issues. These elements contribute to the clarity, resonance, and dynamic character that make vintage PAF pickups so highly sought after.
At the bottom of the baseplate, four small Phillips-head brass wood screws secure the bobbins. These #2 x 1/2" partially threaded screws are distinctive in shape, with brass chosen for its non-magnetic properties, ensuring minimal interference with the pickup's magnetic field. While brass screws are standard, a few verified vintage examples feature steel screws of identical shape, highlighting occasional manufacturing variations in these iconic pickups.
Soldered to the baseplate is a 22 AWG two-conductor hook-up wire manufactured by Belden. This wire features a 2-strand braided metal outer wrap and contains seven individually tinned copper strands twisted together. The strands are then encased in Celanese nylon-type insulation, followed by a waxed black cotton overbraid. Notably, this wire exhibits lower capacitance compared to modern 3-strand counterparts, contributing to the characteristic tonal properties of vintage PAF pickups.
The PAF decal is a waterslide decal made of cellulose, featuring ink-stamped lettering and a silkscreened "Patent Applied For" text in oil-based gold ink. The letters are uniquely spaced, not from a standard font, giving the decal a hand-made appearance. Due to the delicate materials and aging process, original decals often show wear, flaking, and the edges tend to yellow over time. This decal is a key identifier of vintage PAF pickups with historical significance, and it often appears off-center or even upside down. The later Patent No. decal was made using the same process.
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A 1957 Les Paul control cavity
The '50s Wiring: Preserving Clarity and Tone Control
Gibson's '50s wiring is a defining characteristic of vintage guitar design, renowned for its impact on tonal response and player interaction. This configuration refers to the way the tone capacitor is integrated into the circuit—a key factor in preserving clarity and shaping the relationship between the volume and tone controls.
In the '50s wiring arrangement, the capacitor is connected to the wiper (center) lug of the potentiometer, rather than the input lug as in modern wiring. This setup preserves tonal clarity even when the volume is turned down—similar to a treble bleed circuit but without the typical drawbacks. As a result, the pickup’s tone remains consistent, with high frequencies retained even at lower volume levels. This prevents the common loss of brightness, ensuring a clear and articulate tone throughout the volume knob’s entire sweep.
Additionally, the '50s wiring enhances the interaction between the volume and tone controls. Adjusting the tone knob subtly reshapes the sound, and rolling it off can also slightly reduce the overall volume, adding a nuanced character to the playing experience.
While the '50s wiring is often considered the canonical vintage setup, it's worth noting that some guitars from that era actually featured the so-called modern wiring—due to inconsistencies in vintage manufacturing. There is also the ‘60s wiring configuration, which, while similar to modern wiring in tone and behavior, improves shielding by grounding the middle lug on the tone potentiometer, thereby reducing noise and improving overall shielding effectiveness.
The Potentiometer Evolution: IRC, Centralab, and CTS
The International Resistance Company (IRC), founded in 1922 in Philadelphia, Pennsylvania, was a key player in the development of electronic components, particularly resistors and potentiometers. IRC quickly became a leading supplier to industries such as telecommunications, military, radio, and consumer electronics. Known for precision carbon composition resistors, IRC’s components were widely used across industrial and commercial sectors.
By the late '40s, as electric guitars gained popularity, IRC potentiometers were incorporated into designs by leading musical instrument manufacturers, including Gibson. In the early '50s, Gibson commonly used IRC potentiometers for volume and tone control. Around 1953, Gibson began using Centralab potentiometers alongside IRC, marking a transitional period when both brands were used in tandem. By the mid-'50s, Centralab became Gibson’s primary potentiometer supplier. Some early 1956 Gibson wiring harnesses even mixed IRC and Centralab parts, often featuring IRC volume potentiometers from late 1955 paired with Centralab tone potentiometers from early 1956, along with Grey Tiger tone capacitors.
Throughout the '50s, IRC potentiometers underwent several design changes. For example, IRC shifted from solid zinc shafts to brass, split-knurled shafts. The company also updated its date coding system to include one digit for the year and two digits for the production week. IRC eventually became part of TRW Inc. but remained a significant name in the electronics industry.
Centralab, founded as Central Radio Laboratories in 1922 in Milwaukee, Wisconsin, initially focused on manufacturing radio equipment. Acquired by Globe-Union in 1925, Centralab expanded into producing radios and radar-based proximity fuses during World War II. After the war, Centralab concentrated on miniaturization technologies, contributing to the early development of thick-film hybrid circuits and transistors, which laid the foundation for integrated circuits.
By the late '50s and early '60s, Centralab had firmly established itself as Gibson’s primary supplier of potentiometers. During this period, several notable design changes were introduced, including modifications to the fold-over tabs that secured the circuit board to the casing. Early models used three small folds, which were replaced by two larger ones by the mid-1950s, and eventually refined into a simpler shape. The earliest Centralab potentiometers also featured a brass bushing paired with a solid zinc shaft tip, whereas the more common variant used a zinc bushing and a knurled, split shaft. The rotational stop mechanism evolved as well—from a single stop at the left side of the casing to two stops positioned at the top. This redesign reflects a change in the internal resistive track, rendering early and later models mechanically incompatible.
Centralab potentiometers were marked with date and part numbers. The "134" code identified Centralab’s manufacturer, followed by a digit for the year of production, two digits for the production week, a part number (e.g., BA 811-1053), and the specification—such as 500k-C2. The "500k" referred to the nominal resistance, while "C2" denoted a 10% audio taper. In some cases, this information appeared on the top of the potentiometer.
Centralab's 500k potentiometers typically measured between 600kΩ and 700kΩ, staying within a 30% tolerance range. These variations allowed more high frequencies to pass through, contributing to a brighter tonal response. Aging could also increase resistance over time, with some of these potentiometers now measuring over 800kΩ.
The "C2" taper designation referred to a fast audio taper, in which the resistance at the midpoint of rotation measured only about 10% of the total value (compared to 50% in a linear taper). While this might suggest abrupt changes, the fast taper actually enabled smoother transitions, making the early portion of the rotation more usable and responsive. This resulted in a predictable progression, allowing for precise control over volume and tone. The moderate shaft torque struck a balance between ease of adjustment and positional stability. In factory installations, the unused lug on each potentiometer was typically clipped.
Chicago Telephone Supply (CTS), founded in 1896, was a major manufacturer of electronic components, including potentiometers. By the early '60s, CTS had established itself as the preferred supplier in the music industry, known for consistent tapers, tighter tolerances, and improved durability compared to earlier potentiometer manufacturers. Between 1963 and 1964, Gibson transitioned from Centralab to CTS potentiometers.
CTS potentiometers were identified by the manufacturer code "137," followed by two digits for the production year and two for the production week. These potentiometers became the industry standard in Gibson guitars and are still widely used today. While CTS potentiometers generally featured tighter tolerances, they sometimes slightly underread, resulting in a reduction of treble compared to earlier models.
The progression from IRC to Centralab to CTS in Gibson guitars was driven by supplier availability, not deliberate design choices. Still, each brand brought subtle differences in taper, tolerance, and feel—shaping the tonal character of each era.
Originally, Gibson used short-shaft pots on all models, including carved-top Les Pauls, made possible by an angled control cavity that followed the top carve. In 1977, they switched to a flat cavity and adopted long-shaft pots, allowing for consistent knob height without additional routing. Historic Custom Shop models later reverted to the original angled routing with short-shaft pots.
Cornell-Dubilier, Sprague and the Other Tone Capacitors: A Historical Overview
Tone capacitors are crucial components in the tone circuitry of electric guitars, directly impacting how treble frequencies are attenuated as players adjust the tone controls. For vintage Gibson guitars, these capacitors hold both tonal significance and collectible value. From the early '50s to the '60s, Gibson used a variety of capacitor types, and their choices evolved significantly over time.
In the '50s, Gibson’s tone capacitors showed the greatest variation among its electrical components. As long as the capacitance was .022μF, the company sourced capacitors from various suppliers, using whatever was available to meet the high demand of the era.
Among the rarest of early tone capacitors are the so-called "Chicago" capacitors, found in a few early Les Pauls from the trapeze tailpiece era. Though seldom seen, their presence suggests certain batches of instruments may have been equipped with this brand.
Cornell-Dubilier Electric (CDE), founded in 1909 by William Dubilier, is known for producing high-quality capacitors. In 1933, CDE merged with Cornell Radio, and its "Grey Tiger" capacitors became a staple in Gibson guitars during the early to mid-'50s. These capacitors are easily recognized by their large paper tube marked with red, blue, or black ink.
Built using the Paper-in-Oil (PIO) method, Grey Tigers feature a dielectric core of aluminum foil and paper impregnated with castor oil, sealed in epoxy, and coated with beeswax. While slight variations occurred between batches, these capacitors were widely used and respected.
However, Sprague capacitors are most commonly associated with vintage Gibsons.
Founded in 1926 by Robert C. Sprague in North Adams, Massachusetts, Sprague Electric pioneered capacitor technology. The company expanded rapidly, particularly in the post-war era, becoming a major supplier for both consumer electronics and military applications. By the '50s and '60s, Sprague capacitors were used in everything from radios to high-end audio equipment and electric guitars.
Perhaps the most famous Sprague capacitors are the "Black Beauty." These capacitors have a black thermoplastic cylindrical casing with distinctive mold marks, such as two circular indentations and a mold identifier. The examples from the '50s are commonly known as "Bumble Bees" due to their brush-striped color bands: red, red, orange, black, and yellow. Each red stripe represents the digit 2, the orange stripe indicates a .000 multiplier (thus .022μF), the black stripe denotes a maximum voltage of 400V, and the yellow one a tolerance of 20%.
The first version, used by Gibson from around 1956, featured PIO construction—a widely adopted method among mid-century capacitor manufacturers. Although beloved for their tone, PIO capacitors are known to degrade over time. Modern testing often reveals significant value drift—many .022μF caps now measure as high as .035μF after decades of use. While many tone aficionados seek vintage PIO for installation in modern guitars, caution is advised. These capacitors are prone to value drift, heat damage, and general instability. Several tested vintage Bumble Bees are no longer within specification, prompting players to either seek out tested examples or opt for modern equivalents.
As capacitor technology evolved, Sprague transitioned the Black Beauty line to Mylar construction, which improved stability and reduced long-term degradation. Mylar is a brand name for a type of polyester plastic film. These versions initially retained the original color band value coding and began appearing in Gibson guitars by late 1959, although with some overlap. The PIO version can be recognized by the presence of the inner foil layer connector at one of the terminals. The final variant of the Black Beauty caps, introduced around 1960 and used until the early '70s, featured printed text in red ink instead of the color bands, while retaining the same Mylar construction.
Another Sprague-manufactured capacitor, known as the "Phonebook" cap due to its size and appearance, has been documented in late '50s Les Paul Customs and early '60s ES models. The official Sprague designation for this cap remains unknown, and sightings are relatively rare. These capacitors are more commonly associated with Fender guitars, but their presence in Gibsons offers an intriguing glimpse into the company’s sourcing practices during this period.
Astron capacitors were also found in several 1960 Les Pauls. It appears that Gibson briefly acquired a batch of Astron capacitors during this time and used them across multiple models. However, their use was short-lived and specific to certain batches.
By the early '60s, ceramic disc capacitors became the standard not only for Gibson but also for many other guitar manufacturers. Inexpensive, consistent, and reliable, these capacitors were widely adopted and continue to be used in modern production models. Although they lack the mystique and collectibility of earlier PIO or Mylar capacitors, ceramic discs are functionally effective and remain a workhorse in the industry.
The history of tone capacitors in Gibson guitars reflects broader trends in post-war electronics and shifting manufacturing standards. Even with the same capacitance value, capacitors can perform differently due to variations in construction and materials. Factors such as dielectric type, size, and build can introduce parasitic elements like series resistance and inductance, which affect the capacitor's behavior in audio circuits and impact sound quality and performance.
In the end, these unassuming components play a role in the iconic sounds we associate with vintage guitars, making them a key piece of the puzzle for modern builders and tone aficionados alike. The evolution from early experimental designs to the more reliable components of today illustrates how guitar technology has advanced—yet the pursuit of the perfect tone remains as passionate and diverse as ever.
The Evolution of the Switchcraft 3-Way Toggle
Founded in 1946, Switchcraft is an iconic American company that has played a pivotal role in the development of high-quality audio connectors and switches. Among its many contributions, the Switchcraft 3-way toggle switch became a defining component of Gibson guitars, particularly in models like the Les Paul. This simple yet effective switch allows players to select between the neck, bridge, or both pickups.
In the '50s, these components were unbranded. The "Switchcraft" name—cast into the metal frame—was introduced in the late ’50s, marking the company’s growing reputation.
To authenticate a vintage Switchcraft toggle switch, attention must be paid to subtle but important details. The arrangement of the electrical leaves and the way the two stack screws pass through the switch are key distinguishing features. These early switches differ from later models in their internal layout, and the back of the switch is often the most reliable area to spot these variations.
A notable aspect of the toggle switch in '50s Gibson guitars is how it handled the “both pickups on” function, activated in the middle position. Two wiring methods were used during this period: the simpler method connected the two upper terminals directly and linked the lead to the output jack; the alternative routed the pickup leads to separate terminals, with a jumper wire across the back of the switch to join them in the middle position. Both methods functioned identically, though these variations reflect the typical inconsistencies found in Gibson’s vintage wiring.
The switch also plays a crucial grounding role. The two braided wires from the volume potentiometers and the one leading to the output jack were bundled with bus wire, insulated with spaghetti tubing, and soldered to the switch’s ground terminal. This made the toggle switch the central grounding point, ensuring that all components—pickups, volume pots, switch, and output jack—shared a unified ground.
The 1/4" input jack is also a Switchcraft product, further reinforcing the brand’s dominance in vintage Gibson guitar components.
Switch Tips: Material and Design of This Small Detail
From 1947 to 1960, Gibson guitars used switch tips made by Switchcraft from Catalin, a dense phenolic resin valued for its smooth finish and unique aging properties. Unlike modern injection-molded plastics, Catalin was poured into molds as a liquid, creating seamless tips without visible mold lines. Initially pale ivory, Catalin darkened to amber or butterscotch over time due to UV exposure, a key feature that distinguishes vintage switch tips from modern reproductions.
Catalin also has a distinct smell when heated or rubbed, often compared to a mild camphor-like odor. This, along with its aging characteristics, helps collectors and vintage enthusiasts identify authentic switch tips.
The switch tip's design features a slightly elongated shape with a rounded dome that tapers toward the base, ending in a subtle ridge. This ergonomic shape provided a secure grip and enhanced player comfort. Its aesthetic also contributed to the overall vintage appeal of the instrument. Like modern switch tips, it is screwed onto the toggle switch.
After 1960, Catalin was replaced by Plaskon, an injection-molded plastic that was cheaper and easier to mass-produce. Although Plaskon was similar in color, it lacked Catalin's aging qualities and often showed a visible mold line. Plaskon tips were also lighter, and their uniform appearance lacked the unique charm of Catalin.
Inside Vintage Gibson Guitars: A Look at the Wiring Materials
The braided-shield connecting wire is a shielded hookup wire that was commonly used in electric guitar electronics, particularly by Gibson. It consists of two conductors: a central signal core and an outer braided shield, which serves both as the ground path and electromagnetic shielding. In vintage Gibson guitars, this wire is a 22 AWG cable manufactured by Belden. The core is made of seven individually tinned copper strands twisted together and insulated with a white (amber in the early '50s) Celanese nylon-type material, then wrapped in waxed black cotton cloth. The outer braid forms a mesh, woven from two thin strands of wire. This construction provided a durable, low-capacitance wiring solution, though the capacitance difference is minimal over the short internal runs typically found in guitars. In modern instruments, three-strand braided shield wire, such as the type produced by Gavitt, is more commonly used.
Buss wire in vintage Gibson guitars is made of plain tinned copper and was primarily used to connect various components in the circuit, especially for grounding purposes. The 19 AWG buss wire was typically used for the main grounding at the switch and the ground loop connecting the tone potentiometers, while 22 AWG was usually reserved for bridge grounding.
Vintage Gibson guitars also often employed 20 AWG sleeve—commonly referred to as "spaghetti tubing"—made from woven, varnished glass fiber cloth. This heat-resistant insulating sleeve was primarily used on capacitor terminals and grounding buss wire. Yellow, amber, or brown, it helped prevent shorts and ensured safe operation.
Finally, the wire leading to the output jack was generally encased in an 8 AWG black PVC sleeve for electrical insulation.
Tone Control and String Grounding
Throughout the '50s, Gibson used various methods to connect tone potentiometers to the ground plane in its electric guitars. While ES models and Juniors typically employed straightforward techniques—such as soldering the braided shield of the output jack lead directly to the tone potentiometer casing or relying on the braided shielding of adjacent leads—the control layouts of guitars like the Les Paul Standard were more complex, requiring additional grounding considerations.
In these guitars, the toggle switch served as the main grounding node, with all components ultimately referencing this point. However, the tone potentiometers were an exception, as they were not directly grounded to the switch. Instead, they relied on a shared ground path through the volume controls. This grounding method evolved over time.
In the early '50s, a typical setup involved a ground wire connecting the neck volume potentiometer to one of the tone potentiometers. A short jumper wire then linked the neck and bridge tone potentiometers, effectively chaining them together. During this period, spaghetti tubing was used for insulation; later, the buss wire was left bare, with only a few exceptions.
Subsequently, Gibson adopted a “U-shaped” grounding system. This method employed a single, continuous length of buss wire that began at one volume potentiometer, passed through both tone potentiometers, and terminated at the second volume potentiometer, creating an open horseshoe arching around the control cavity.
In another variation, Gibson used two short segments of buss wire—each linking each volume potentiometer directly to its corresponding tone potentiometer. This layout eliminated any connection between the tone potentiometers themselves.
From an electrical standpoint, all three grounding schemes were functionally equivalent. In each case, every potentiometer involved had a single ground solder point, positioned for practical assembly. While vintage wiring often has a distinctive visual appeal, it was not always uniform or neatly executed.
Gibson's approach to string grounding evolved alongside changes in bridge design. On the earliest trapeze-equipped Les Pauls, the string ground wire was routed through a hole drilled for the strap button to the mounting bracket of the trapeze bridge, similar to hollow body models. These guitars also featured an extra routed channel specifically for this purpose.
With the introduction of the stud-mounted wraparound bridge, Gibson implemented a more efficient system. A thin ground wire was routed from the bridge pickup cavity to the treble-side tailpiece stud hole. Once the stud bushing was pressed into place, the wire was grounded by either soldering it to the braided shield of the pickup lead or routing it through the diagonal control cavity channel and soldering it to the casing of the neck volume potentiometer. The method chosen depended on the assembler.
In one-piece body models—such as Les Paul Juniors, Specials, and Customs—Gibson used drilled holes instead of routed channels to connect cavities. In these guitars, the string ground wire was typically run through a small hole from the pickup cavity to the control cavity and soldered directly to a potentiometer casing. The small diameter of this hole and the shallowness of the pickup cavity often made it impractical to wrap the ground wire around the pickup lead.
By late 1955, the introduction of the ABR-1 bridge allowed for a more streamlined grounding process. A wire could now be run directly from the treble-side tailpiece stud to the control cavity, emerging near the neck volume potentiometer. This method became dominant during the late '50s. However, when tremolo systems such as the Bigsby were installed, Gibson reverted to earlier grounding techniques. In these cases, the ground wire was routed from the bridge pickup cavity to the ABR-1 post hole, mimicking the wraparound-tail method. As before, the wire could either be soldered to the pickup lead or extended to a potentiometer casing.
In summary, Gibson's tone potentiometer and string grounding practices during the '50s were shaped by a combination of technical function, production convenience, and evolving hardware design. While collectors and enthusiasts often focus on subtle visual or material details—such as wire gauge, insulation type, or routing style—these variations had no appreciable impact on tonal performance. All methods shared a common goal: to complete a robust and quiet ground path that preserved the signature sound of vintage Gibson instruments.
The Varitone Circuit
One of the most distinctive features of vintage Gibson guitars was the introduction of the Varitone circuit, a specialized tone control system that provided a broader range of tonal options. First introduced in the early '60s, the Varitone was primarily featured in the Gibson ES-345 and ES-355 models, though it would later appear in other semi-hollow and hollow-body guitars.
The Varitone was a complex circuit that allowed players to select different capacitors and inductors in the signal path, essentially altering the frequency response and offering a variety of pre-defined tonal shifts. The control was typically located alongside the tone and volume knobs, often replacing the standard tone control with a multi-position rotary switch.
Each position on the Varitone switch engaged a different combination of capacitors and inductors, enabling players to choose from a wide range of sounds—from brighter, more biting tones to deep, mellow sounds that emphasized the mids. This offered guitarists a level of tonal versatility that wasn’t commonly available on other guitars at the time, allowing for more tonal exploration within a single instrument.
While the Varitone circuit is often associated with jazz and blues players, it has found its place across many genres. The versatility it provided made it highly sought after by musicians looking for unique sounds. However, the system’s complexity contributed to its decline after the early '70s, as simpler tone-shaping options gained popularity.
Stereo Output and the Stereo Gibson Models
Another key innovation from Gibson was the development of stereo wiring, most notably utilized in their ES-355 model and other semi-hollow or hollow-body guitars. Stereo guitars featured dual output jacks, allowing the player to split the signal into two separate channels, which could then be processed or amplified independently.
The stereo configuration enhanced flexibility in live performances and studio settings, offering a wider soundstage and greater separation between the instrument’s various elements. This made it ideal for use with two amplifiers, enabling the creation of distinct sonic textures—such as using one amp for the dry signal and another for processed or delayed effects.
On these guitars, the dual output jacks facilitated an immediate stereo effect, providing a rich, expansive sound that stood out in a mix. This feature was particularly useful for experimentation, marking an early example of stereo processing in electric guitars.
Additionally, Gibson developed models with a "Varitone Stereo" system, where the Varitone circuit was integrated with the stereo output. This further increased tonal flexibility by allowing each channel to respond differently to the selected capacitors and inductors, offering even more dynamic tonal exploration.
Written by Giuseppe Fumuso