When it comes to vintage spec PAF pickups ThroBak gets many requests for detailed descriptions of the Alnico magnets used in them as it relates to pickup voice and feel. So in response I have packed as much info as possible into this somewhat epic blog post. I hope you find it helpful.

A key component of vintage PAF pickups is the Alnico bar magnet. Required to make a functional PAF guitar pickup, Alnico bar magnets play an important role in shaping the EQ profile, picking dynamics, perceived output and response of a P.A.F. humbucker pickup.

Throughout the vintage PAF pickup era Gibson used a variety of sizes and grades of Alnico bar magnets from different USA Alnico magnet manufactures. At ThroBak we offer 8 key varieties of vintage PAF pickup spec Alnico magnets. These USA formulated and cast Alnico bar magnets come standard in ThroBak P.A.F. pickup reproductions as well as for our P90 pickup reproductions. We also offer the same magnets for purchase here on our website for those that like to experiment with magnet swaps in their humbucker pickups. You can find a short description of magnet properties on our Alnico magnet product page but this post is meant to provide a more detailed history of the magnets and their tonal properties in PAF humbucker pickups.

It should be noted that the tonal properties listed below do not necessarily translate the same to a P90 guitar pickup or other styles of Gibson and Fender guitar pickups that use Alnico bar or rod magnets. The details below relate specifically to PAF style guitar pickups.

USA Made Alnico vs Overseas Made Alnico

As mentioned earlier vintage PAF pickups used Alnico magnets made in the USA by a several of companies. Due to variations in heat treating and formulations between companies, magnets of the same grade but from different manufactures exhibit unique sonic properties when put into a guitar pickup. To duplicate these variations ThroBak offers a variety of Alnico magnets of different Alnico grade and different Alnico variations within a specific grade. This allows ThroBak accurately reproduce the variations of the best sounding Alnico magnets found in vintage PAF pickups. ThroBak Alnico magnets are custom formulated and cast in the USA in "Full Heat" batches using legacy formulations still on file in the USA or with formulations created from  destructive analysis of vintage magnets we provide the magnet maker's lab. Fortunately the legacy formulations of USA magnet makers Permanent Magnet Company, Arnold Magnetics, Thomas and Skinner and General Magnetics are still available to ThroBak due to our willingness to order the "Full Heat" quantities required to reproduce these magnets. As of the writing of this post ThroBak's overhead cost for maintaining stock of the full variety of Gibson PAF bar magnets is $50k. This does not include the even larger overhead cost of maintaining the full vintage variety of USA made rod magnets for Fender style pickups. It's a big expense but we feel it's worth it to make the best P.A.F. and Fender reproduction pickups in the world.

Our past experience with overseas magnet makers clarified the value of the USA legacy Alnico formulations in creating the most accurate PAF pickup reproduction possible. Compared to USA made Alnico magnets of the same grade, overseas magnets very often charge to a higher gauss and are not as consistent batch to batch as ThroBak USA formulated and cast USA made Alnico magnets. Not surprisingly overseas magnets also do not have the same vintage voice as the legacy formulation USA made Alnico.

Alnico Magnets and EQ

Before we talk about specific grades of Alnico it's important to understand a few key concepts about how the different grades of Alnico bar magnets used in PAF pickups affect the tone and response of the pickup. First among these affects is EQ and how the Alnico magnet influences EQ response. Due to the proximity of the Alnico bar magnet to the coils in a PAF pickup, the metal mix of the Alnico magnet has a direct impact on the inductance of the assembled PAF pickup. For the guitar player these changes in inductance amount to subtle differences in EQ between the different grades of Alnico when compared against each other in the same pickup. This difference in inductance is unrelated to magnetic strength and is simply a function of the metal mix of the magnet. An uncharged Alnico magnet will show the same change to inductance of the P.A.F. as a fully charged Alnico magnet.

Oriented vs Unoriented Alnico Magnets

Given the above information about metal mix it would seem logical to conclude that the variety of voices due to Alnico magnets in a P.A.F. pickup come down to metal mix differences between Alnico grades. However the details that affect the voice of an Alnico magnet are more complex than just metal mix differences. Alnico magnets must be heat treated after casting in order to have magnetic properties. This process of heat treating can be manipulated to change the strength of the magnet and in turn affecting the magnet's voice in a P.A.F. pickup.

One key way to manipulate the strength of the magnet is through orientation of the magnetic grains within the Alnico during heat treating. The first variation of the heat treating processes allows for the magnet to be charged in any direction, these magnets are referred to as unoriented. This unoriented heat treating process is part of part of the standard specification for Alnico 2, 3 and 4. Additionally some Alnico 5 magnets used in vintage PAF pickups are unoriented even though it is not the standard specification for an Alnico 5 magnet.

The second heating process variation aligns the magnetic grains within the Alnico in one direction, creating a magnet that can only be charged in one direction. This creates a magnet that holds more charge than an unoriented magnet. These more efficient magnets are referred to as oriented. For PAF pickups the A5 magnet is to be oriented according to A5 spec although some A5 PAF magnets are unoriented making them hold less charge as an oriented A5. Whether this difference was purposeful or an accident during heat treating is an open question. Whatever the case ThroBak offers two varieties of oriented A5 and two varieties of unoriented A5 in order to have a full range of vintage PAF Alnico 5 voices.

In a guitar pickup an oriented magnet is characterized by higher perceived output compared to an unoriented magnet of the same grade. This is due to the oriented magnet's ability to hold more magnetic charge than an unoriented magnet. Also pick attack is affected by orientation with an unoriented magnet having a slightly more compressed pick attack and the oriented equivalent having a faster and slightly less compressed pick attack.

Long Magnets vs Short Magnets

During the vintage PAF period Alnico bar magnets were made in two lengths. The first size is referred to as a long magnet which measure 2.5" long. Most PAF era pickups from 1957 to 1959 use long Alnico magnets. These magnets can be either Alnico 2, 4, 5 oriented or 5 unoriented and in rare cases Alnico 3. The second Alnico magnet size is called a short magnet, measuring 2.35" long. These short magnets start to appear in small numbers in 1958 and by 1960 they transition into the primary magnet used in a PAF. These short magnets can be Alnico 2 or oriented Alnico 5 with Alnico 2 being the most common during the early years of their introduction. 

The most notable distinctions between these magnets is the short Alnico 2 exhibits an increased mid content compared to its long A2 counterpart. This difference was so pronounced that I sent a vintage P.A.F. short magnet to one of our USA magnet makers for duplication thinking it was A5 due to the magnet's tonal profile in a pickup. However after lab analysis it was confirmed that the short magnet was in fact A2 and not A5. The resulting formula became the ThroBak short A2 we use in MT-102B MXV pickups and the ESG-102B ThroBak PAF repros. The magnet manufacturer even produced spec records for short A2 being made as recently as 1969, dispelling the conventional wisdom that all short magnets in vintage Gibson pickups are A5.

One other interesting distinction is that vintage Gibson short oriented A5 magnets have an audibly more aggressive and punchy character in a guitar pickup than the long oriented A5 magnets Gibson used. This tonal difference  comes down more to differences in A5 formulation and processes between magnet makers of the vintage era rather than a difference due to magnet length.

Magnetic Strength and Pickup Output

Perceived output of a P.A.F. style pickup is a combination of coil resistance and the amount of charge the Alnico magnet holds. When comparing pickups of the same resistance, perceived output will be higher in the pickup with the stronger magnet. This contributes to pickups with oriented A5 magnets having a higher perceived output and pickups with long A3 magnets having the weakest perceived output, A3 being the weakest of Alnico grades.

Alnico Magnet Grades in P.A.F. Pickups

Below are the ThroBak Alnico magnet descriptions from the ThroBak Alnico Parts Page but with more in depth context as it pertains to vintage PAF pickups and ThroBak reproduction pickups.

A2 long / Scooped mids, chimey highs, warm sweet tones, loose feel.

Many associate the sweet compressed tone and feel that long A2 provides with tone of a vintage PAF. Vintage PAF pickups often have these long A2 magnets. They can be found primarily in vintage PAF pickups from 1957 - 1959. The top selling ThroBak SLE-101 MXV and KZ-115 MXV sets and our EdA-Custom MXV set showcase the long A2 in both bridge and neck pickups. The DT-102 MXV set uses this same long A2 in the neck position creating a unique chime in the middle position when mixed with the Long unoriented A5 bridge pickup.
  
A2 short / Scooped mids, spankier tone than long A2.

Vintage spec short A2 still has a scooped mids character but with more prominent mids than long Alnico 2. The Short A2 low end is also snappier than a long A2 magnet. Short A2 magnets are most commonly found in starting in 1960 but have also been found on rare occasions in 1958 era pickups. The ThroBak MT-102B MXV set as well as the ESG-102B Custom, PRE-T-301 MXV and '70/Select MXV pickups feature short A2 magnets. Short A2 often shows up in the neck position in combination with a short A5 bridge pickup magnet. We think this may have been an effort by Gibson to equalize output between two pickups of similar resistance by putting the lower charge A2 magnet in the neck position thus reducing the perceived output of the neck pickup.
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A3 long / Very weak, nice clarity for use in P90 pickups but very low output for PAF pickups.

Long A3 is the weakest and rarest magnet to be found in a vintage PAF pickup. Long A3 magnets voice the P.A.F. pickup with less output, reduced picking dynamics and less harmonic content and overtones than the other more common Alnico grades found in a vintage PAF. We think the rarity of A3 in a P.A.F. is probably due to Gibson recognizing the limitations of A3 in a P.A.F. pickup. Because of these tonal limitations, we at ThroBak only use the A3 magnet in the DS-55 where the reduced output of A3 balances well with the A4 of the DS-55 bridge pickup. In contrast to A3's use in a PAF pickup, A3 sounds great in a P90 where two A3 magnets increase the overall magnetic strength and also in early Fender pickups where the A3 rod magnets deliver more magnetic charge to the strings than the single bar magnet of a vintage PAF pickup.

A4 long / Balanced mids, treble and low end, drier toned than A2.

Long A4 is commonly found in '57 through '59 era P.A.F. pickups. Long A4 has a slightly higher perceived output than long A2. Long A4 is characterized by a drier voice than the wetter and more compressed voice of long A2. Long A4 still has compression to pick attack but not as pronounced as the compression of long A2. Long A4 has more emphasis on the mids than long A2. Overall the tone is balanced but there is a wider frequency spread from low to high with long A4 than with any other Alnico grade. Because of this A4 can have a harsh treble relative to the low end if used in an already bright guitar. ThroBak MC-102B Custom MXV pickups come standard with long A4 magnets in neck and bridge pickups and long A4 is available for the KZ-115 MXV pickup set on request.

A5 long oriented / mid dominant, focused tone, jazzy cleans.

Long Oriented A5 is most commonly found in '59 era P.A.F. pickups. Long oriented A5 is characterized by a full, center mid dominant voice. Pick attack is fastest of the P.A.F. era Alnico grades with a full focused feel that still exhibits the signature pick attack compression of Alnico, however the pick attack compression is not a pronounced as long A2 compression. The higher magnetic charge held by long oriented A5 gives pickups with it installed a higher  perceived output. Dirty tones with long oriented A5 are quick and authoritative and cleans are full and focused. Long oriented A5 is the standard magnet in ThroBak PG-102 MXV pickups and are available on request in the KZ-115 MXV set.

A5 short oriented / mid dominant tone, fatter toned than long oriented A5.

Short Oriented A5 begins to appear in '60 era P.A.F. pickups and continued to be used in Gibson humbucker versions though the 1960's. Short oriented A5 makes a pickup more aggressive sounding than long oriented A5. Short oriented A5 voice is characterized a punchy, chunky, lower mid dominant aggressive tone. ThroBak ER-Custom MXV set comes standard in both neck and bridge pickups and is the standard magnet in the bridge of the ESG-102B Custom MXV, Pre-T-301 MXV and DW-102B MXV pickup sets.

A5 long unoriented (Illinois) / Great low end clarity with good mids.

Long unoriented A5 may be best characterized as the unicorn of long Alnico magnets found in vintage P.A.F. pickups. Found sometimes in '58 and '59 era P.A.F. pickups their use was first confirmed by Tim Shaw during his P.A.F. research in the 1980's for Gibson Kalamazoo. Shaw concluded that the unoriented nature of these A5 magnets was perhaps a result of a mistake in heat treating causing a small percentage of A5 magnets to be unoriented. After conversations with engineers at Permanent Magnet Company I believe that unoriented A5 magnets may have been specifically requested by Gibson. Whatever the case, long Illinios Unoriented A5 magnets have similar magnetic strength to long A2 making perceived output the same between both. However IL Unoriented A5 has a more center mid dominant EQ than long A2 and a crisper low end than long A2 due to the different inductance profiles of these two magnets. Illinois long unoriented A5 magnets are standard in the neck and bridge pickups of our popular SLE-101 Plus MXV pickups. The are also standard in the bridge pickup of the DT-102 MXV set.

A5 long unoriented (Indiana) / Less low end clarity more treble snarl, good mids

Similar in character to the our Illiniois Long unoriented A5, Indiana long unoriented A5 was made for ThroBak by the now out of business Permanent Magnet Company of Indiana. Fortunately we have the melt records of these and the other Permanent Magnet Company legacy Alnico mixes and an agreement with Arnold Magnetics to make these magnets for ThroBak whenever we need them. Tonally these magnets have just a little less power and a little less low end treble content than Illinois unoriented A5 giving these magnets a little more upper treble snarl. IN unoriented A5 magnets are used in the neck pickup of the JW-102B Custom set.

In conclusion

The variations in tone between vintage P.A.F. pickups is often chalked up to mysterious random circumstances of the 50's era Gibson world. While there is some truth to the perceived random specification differences of vintage pickups, a closer look reveals that when it comes to magnets the tone variation they provide is not a mystery. At ThroBak we feel there is no unsolvable mystery when it comes to vintage guitar pickups. We look closely at all the details of winding, wire, magnets and material specs and spare no expense in duplicating them for the sake of great vintage guitar pickup tone!

Jon Gundry

I just finished up another vintage P.A.F. pickup repair today. This time it was a P.A.F. spec Patent # pickup likely dating from 1965. This era of Gibson humbucker is essentially a P.A.F., however with a chrome plated cover and chrome plated pole screws and the white and black start and finish wires typically indicating no internal start lead. In all other respects this era of pickup mirrors the same specs as a late short magnet P.A.F., butyrate bobbins, short Alnico 2 magnet, plain enamel magnet wire and the wire pitch, or turn per layer count, that matches the variations of PAF sticker pickups. The similarities with a PAF sticker pickup have made these ever more desirable in the used market for those seeking vintage PAF tones with a somewhat lower price point.

The pickup pictured required a screws coil rewind. Screw coils in even a covered humbucker are the most likely to fail internally as they are vulnerable to sweat, beer, whatever liquid that enters the square hole next the E string adjustable pole screw. Like with all rewind candidates I unwind the coil by hand in search of a possible wire break and also to establish the turn per layer count of the coil so we can choose the correct wire pitch and machine so the rewound coil will have all the properties of the damaged original coil.

However while unwinding this original coil it became apparent that the turn per layer did match any of the the wire pitch data we have from our vintage PAF, Patent # or even T-Top repair records. Knowing the coil was 100% original, I figured there must be a simple explanation for a wire pitch setting so far outside of our repair records data. With a little thought I posited that the wire pitch for this pickup 42awg wire pickup was likely the same wire pitch as the wire pitch for a 38 awg Charlie Chrisitian pickup.  With a quick test on the ThroBak Meteor ME-301 coil winder I confirmed that the pickup in need of a rewind, was in fact wound at the 38 awg setting on the Meteor ME-301, (just an FYI for any pickup makers reading this, the 38awg setting on the ME-301 is not what you would expect for 38 awg wire).