Great Article in Vintage Guitar Magazine By: Gil Hembree

Seth Lover
Humbuckers And other Lover innovations

 

A noted creator, Seth Lover’s achievements include numerous amplifiers and circuits, but none have been so highly recognized as his humbucking pickup, which became the Patent Applied For (P.A.F.) humbucker. The following is excerpted from an interview with Seth Lover conducted by VG’s Stephen Patt in 1996. At the time, Lover was working with pickup designer Seymour Duncan on the SH-55 humbucker, more commonly known as the Seth Lover Model. Lover passed away on January 31, 1997.

Vintage Guitar: Who got you started on the path of electronics?
Seth Lover:

I was born in Kalamazoo, Michigan, on January 1, 1910. In the early 1920s, a schoolteacher in Pennsylvania began helping me with electronics projects. I was living with my grandparents at the time, and we used to get the Philadelphia newspaper; the radio section showed how to build different circuits. I guess my first project was a one-tube radio, which worked pretty well. My grandparents had died in the 1920s, and I decided to join the Army, where I worked with electronics. And when I hit the end of my term in 1931, I took a radio course from a Washington, D.C. company. It was actually my second – the first was in 1925, while I was working on a farm.

How did your first radio business come about?

After my second course, I went into business in Kalamazoo, repairing radios and the like at the Butler Battery Shop. We’d recharge batteries, repair radios, and install them. But when Butler died, we started a shop at 465 Academy. Eddy Smith, an orchestra leader at Long Lake, was a good customer. I used to build amplifiers for them. The poor guitar player would be playing next to the piano, and you could see him moving his hands, but for the life of me you couldn’t hear him play one note! If they let him get close to the microphone, he could be amplified and heard.

 

In 1935, I went to work for M&T Battery, doing the same thing. Then in ’41, Walter Fuller wanted me to come to work for Gibson. They were buying amps from a Chicago company, the EH-125, the 150, and the 185. We’d plug in the tubes and test them – I was a troubleshooter. And when World War II came along, I joined the Army again.

In what capacity?

They offered me a Second Class Radioman rating, and I ended up in the Navy. I was sent to Connecticut, then to Treasure Island, near San Francisco, to radio electronics school. That August, I received my First Class rating and was sent to teach electronics near Washington, D.C. Most of my time during the war was spent teaching.

 

In 1944, I had to go to sea [on] the USS Columbus, which was being built in Massachusetts. I was sent there and began checking installations and spare parts, and a little later we were out to sea. Well, about 500 miles out, the drive shaft broke, and we had to turn around. In order to get at the thing, they had to cut a hole through all the decks. And before they got the darn thing fixed, the war was over!

Did you resume your electronics work?

Yes. I went back to work for Gibson and stayed for a couple years, until the Navy built a training station in Michigan. With my Chief’s rating, I was asked to work for them for $5,000 per year, which was a lot of money back then. Gibson was only paying me $3,000. A few years later, they wanted to transfer me to Minnesota. Ted McCarty asked me to build a special kind of pickup, which I did by hand. Then he decided Gibson could afford to pay me what I was getting in the Navy, so I was back with Gibson in 1952.

What were some of your earlier designs?

Before I’d gone into the Navy, I’d begun to design an amplifier. The tremolo circuit in typical amps at the time "putted" along if there was too much depth. I found a way to get a tremolo without any noise, using an optical device, and Gibson was building it while I was in the Navy. So in 1952, I began designing other amp circuits. In ’55, I got the idea for this humbucking pickup. When a single-coil pickup, got too close to an amplifier, it would make a godawful hum.

 

I had designed an amplifier – the Model 90 – which had a special humbucking choke, and figured I could use the same concept on the pickup itself. It was quite simple, really – just two coils opposed, and they’d pick up the hum and just cancel out. I designed it into the tone circuit of the amplifier, and if you’d swing to one end it would wipe out the bass, to the other extreme it would wipe out the treble. So, the pickup was similar in concept.

When did your humbucker actually begin production at Gibson?

We starting building our version in 1955, even though we didn’t have a patent, and that’s when they got the "PAF" stickers to put on them. When we finally were granted our patent, we changed the sticker to one with a patent number, but we actually printed the wrong number on the sticker, one that matched our tailpiece. This way people who sent away for copies of that patent didn’t ever get a copy of the pickup (laughs)! We were replacing the P-90, and there were other single coils being used, especially on steel guitars. I did make a humbucking pickup for steels that worked particularly well. The Gibson Electraharp had my pickup on it, and it was a whopper, but they didn’t build too many of them. It was quite expensive.

 

I bet you’ll like this. [Seth rummages through an old cabinet, and pulls out a cloth-wrapped something.] This is my PAF prototype. It has a stainless steel cover. There’s no high-conductivity in stainless like copper and brass, so it worked well. When the salesmen saw this with no adjustment screws, it was like breaking their arms! They just didn’t have anything to talk about. So, next came the punched-out holes and the adjustment screws.

Was there anything you did specifically for Epiphone?

Epiphone guitars used to have a bunch of pushbuttons, and every time you’d change settings, it’d go "clunk!" I designed a switch with a rocker panel and a magnet to hold the position. My version was never used, but it worked awfully well.

 

And on the Epiphone mini-humbucker, I changed the design to offset the screws and look different – maybe better in some ways – than the Gibson humbucker with its straight screws. It wasn’t quite as loud as the Gibson version, with fewer turns of the coil, and it was a bit trebly. But it did the job.

What prompted your shift from Gibson to their main competitor, Fender?

I stayed with Gibson until 1967, and then had an offer from my friend, Dick Evan, who was Fender’s chief engineer. Now, while I designed most of the amplifiers and pickups, I never did hold that title. I was just a designer. CBS had bought Fender, and they were kind enough to offer me a job. He sent me a ticket to come out [to California] and talk. And they offered me $12,000 per year. I was only getting $9,000 at Gibson.

 

So I came out and did design quite a bit of stuff for them. But the thing was, if the front office didn’t ask for something, they just weren’t interested in anything you’d come up with.

How did you and Seymour Duncan join forces?

After the patent ran out, Seymour started making the pickups, and he did an awfully good job, not just in appearance, but in materials and workmanship and sound. Everything, down to finest detail, was intact. We had used plain enameled #42 wire. A lot of people would use plastic-coated wire, but the results weren’t the same. We used nickel-silver on the covers originally, sometimes called German silver, again due to its low conductivity. You can’t solder stainless steel, so the nickel-silver worked better. And that’s what you see on these special Duncan-Lover pickups. It’s really faithful to the original. The SH-55 will have my stamp of approval on it, and I’ll even get a small royalty on each sale. Now, that’s something that Gibson never got around to giving me! My name doesn’t show up in too many of these history books, and maybe they didn’t value design in those days. I guess that’s why they never paid me much [a wicked glint in his eyes signals that Seth is gently pulling my leg]. I did a lot of work, and now it seems to be getting recognized.

Vintage Gibson Humbuckers Specs:

1956 – 1957 (“PAF”): Long (2.5”) Alnico 2, 3, 4 and 5 magnets used randomly, brushed stainless steel cover, *no* PAF sticker, automatic traverse wound with manual-stop (until bobbin was “full”), #42 plain enamel wire (purple), individual coil ohm differences, black leads on coils, ohms vary from low 7k to high 9k, black PAF-style bobbins (”square in circle” with holes). PAFs first installed on Gibson lap-steels in ‘56 and then guitars in ‘57.

1957 – 1961 (“PAF”): Long Alnico 2, 3, 4 and 5 used randomly (A2 most common), nickel cover, “Patent Applied For” sticker, automatic traverse-wound with manual-stop, #42 plain enamel wire (purple), individual coil ohm differences, black leads on both coils, ohms vary greatly – generally between 7k and 10k, black and cream (early-’59 thru mid-‘60), all bobbins black again by late ’60, PAF-style pickup bobbins.

1961 – 1962 (Late “PAF”): Smaller (2.37”) Alnico 5 magnet used for remaining production (all transitioned by July ’61), nickel cover, PAF sticker, automatic traverse-wound with manual-stop, #42 plain enamel wire (purple), black leads on both coils, individual coil ohm differences, ohms averaged 8.0k by ‘62, PAF-style bobbins.

1962 – 1964 (“Patent no.”): Alnico 5, nickel cover, “patent no.” sticker (mid-’62), polyurethane wire (starting ‘63), black/white lead wires, “auto-stop” winding starts circa-’62, PAF-style bobbins, usually 7.6k – 8.0k ohm.

1965 – 1967 (Late “Patent no.”): Alnico 5, polyurethane wire, “patent no.” sticker, bobbin wires white, Chrome cover (starts mid-’65), more durable and flatter bobbins with no “square in circle” hole circa-‘65, ohms usually between 7.4k – 8.0k. Gold-plated PAFs used in arch-top electrics as late as 1965 – “Varitone” guitars had gold-plated pickups with one pickup having a reversed magnet. This pickup style was used far less than nickel-plated pickups, thus inventory lasted thru 1965.

1967 – 1980 (“T-top”): “T” on bobbin top, Chrome cover, Alnico 5, polyurethane wire, automated winding begins ‘65 – ‘68, some ’69 – ’73 pickup covers embossed “Gibson”, “patent no.” sticker on baseplate ‘67 – ‘74, (patent number metal-stamped beginning 1974), ink stamp with date ‘77 – ‘80, ohms average 7.5k – consistently reading between 7.3k – 8.0k.

General Pickup Tech:

The following pickup article is based on years of pickup related research, experience and experimentation. It’s written to be accessible to both the average guitarist and those who appreciate technical description. If you’re interested in pickup tech and tone, you will get a lot out of it after careful reading.

Alnico Magnet Types and Gauss
The II thru V Alnico numbering system is used to indicate the specific alloy each type of Alnico magnet is composed of. Alnico stands for ALuminum, NIckel, and CObalt. Other than iron (which comprises about 50% of all Alnico magnets), these are the main metals used in Alnico magnets – plus all grades but Alnico IV have a bit of copper in them too. And, interestingly, Alnico III contains no cobalt. So, we see the recipe for each Alnico grade is different, with the ratio of metals in each alloy varying quite a bit.

Magnetic flux is measured in Gauss – this is an indication of how strong a magnet is capable of being. Magnetic field intensity is measured in Oersteds. Technically speaking, the strength of a magnet is best measured as an approximate combined product of the Gauss and Oersteds. This is somewhat analogous to how electrical power in Watts is the product of Volts and Amps (Volts x mA = Watts). For instance, 40 mA at 250 volts (40 x .250) produces 10 watts per tube, and the same 40 mA at 500 volts (40 x .500) produces 20 watts. So, when considering magnetic strength, ultimately, both gauss and oersteds are factors. Yet, I’ll keep the scope of this article to follow to the more commonly used measurement gauss.

Alnico III actually possesses the weakest gauss of all commonly used Alnico magnets – less than Alnico II, IV and V. That said, you can still have an Alnico V magnet that’s weaker than an Alnico II magnet, because magnets aren’t always fully charged. Yet, Alnico V has the capacity to hold a stronger magnetic charge than Alnico II, III or IV. A weaker a magnet lowers the resonant peak and a stronger magnet will increase the resonant peak and brightness audible to the ear.

Following is some data regarding accurate gauss meter readings on approx 80 Alnico magnets. The magnets checked were Alnico II, IV and V – both polished and rough cast had the following readings:

New Alnico II magnets measured at gauss levels ranging from 22 to a high of 35, with most in the 25 to 30 range. Alnico IV magnets ranged from 22 to a high of 36, with most in the 32 to 35 range. The Alnico V magnets tested were all from older Gibson “T-top” pickups – 20+ years old, and these all measured in the 25 to 30 gauss range, with most reading 25 to 27 gauss. So, interestingly, older “T-top” pickups show moderate gauss level readings for Alnico V. Gibson pickup magnet gauss readings, on both Alnico II and V magnets, consistently averaged 25 to 30 gauss on the late-‘50s thru the early-‘70s guitars.

A Burstbucker Alnico II rough cast magnet had the most consistent reading along it’s edges than all the other magnets tested, with a gauss level of 25. I was expecting to see a gauss range that defined the different grades, but there were some unexpected results. Alnico V magnets of the “T-top” era had notably lower than expected readings. And, except for the Burstbucker magnet, all the magnets were stronger towards one end of the magnet. This could possibly have tonal implication on magnet orientation in the pickup. Conversely, newly recharged Alnico II magnets in testing spiked out higher towards the center of the magnet.

The type of magnet in a pickup can have more impact on tone than winding resistance when dealing with modest ohm variations of 1 – 2k. You can have a humbucker reading 9k with an output approaching a single-coil. And, conversely have a Humbucker reading 7.5k that sounds like a typical “hotter” wound pickup, as we see with some of the Alnico V magnet pickups of the Gibson “T-top” era. Output and tone depends as much on magnets as winding types, not to mention everything else in the chain like pots, caps, etc.

So, the actual pickup tone type is highly dependant on the magnet and the resistance/windings, as a pickup with a dead magnet will produce 0% output! Additionally, long magnets (PAF-style) are a bit punchier and have better definition than the short magnets, which can sometimes produce a slightly “smeared” sound. Though magnet type can compensate for this, as Alnico V’s additional output, punch and brightness balanced out the shorter magnet size Gibson used beginning 1961.

Additionally, the stud side of the coil actually has slightly more output than the adjustable side on a traditional humbucker. There is a direct connection to the magnet inside the pickup on the stud side, while the adjustable pole extends out the bottom of the pickup. And, there is a slight loss of magnetic field and energy out the bottom of the pickup.

Bobbins, Wire and Winding
A pickup’s treble response is related to the magnet strength interacting with the windings. Think of it as a bell curve. The more winds, the brighter the pickup gets, but only up to a certain point. After that point more winds take away treble. The stronger the magnet the more winds you can add before the treble starts to drop off. Yet, all other factors being equal, inductance increases and treble response decreases, the higher the number of winds.

Resistance is only one indication of a pickup’s overall output – it tells a lot about the actual character of a pickup only when one consider the magnet that is used with it. And, bobbin types are key – skinny and tall coils produce a clearer sound than short and wide coils, all other factors being equal. Also, you can have a pickup with a higher resistance that has less output if the wire gauge is thicker or magnet gauss is lower than the pickup being compared. Or, you can have one pickup that is lower resistance with higher output if the wire is smaller diameter. Additionally, with tight wound coils the wire stretches a bit, which will give a higher resistance reading, because of the additional wire length. Loose winding generates a brighter tone, because with two identically sized coils wound from the same wire, the looser coil will have fewer winds than the tight coil.

Resistance is actually measuring the length of wire used in a coil and doesn’t necessarily indicate how many turns are used, as wire thickness and bobbin sizes vary. If a pickup is longer or larger, it will have the same resistance with less output due to the lower turn count. Turn count is really what determines output, but seeing how there is no way to count turns on an already wound pickup people use resistance for output comparison.

Fewer winds will have an audible effect, because the pickup will have less inductance, which affects the frequency response – making the pickup brighter. The pickup inductance interacts with the guitar volume/tone controls, guitar cable capacitance, and amplifier input load to create an EQ network. More inductance causes more highs to be lost in this EQ circuit. This also means that resistance ’specs’ are misleading, because the turns count is what really makes the pickup sound they way it does. Inductance itself is related to the square of the turn count, so a small error in turns becomes a large error in inductance. By winding to a resistance value, you can’t get the turns count right because you don’t know what tension other pickup makers are using. But, by winding to a specific turn count or inductance value, you stand a much better chance of winding a successful pickup.

A traditional PAF pickup uses 42 gauge plain enamel insulation wire. Then there are other types of insulation like polyurethane, which would mean the coil wire might have a different overall diameter, so not all 42 gauge wire is created equal. There are also lighter wires, such as 43 or 44 gauges. In general, thinner wire will create a more high-frequency loss than thicker wire, all other factors being equal. Interestingly, in this same coil, polyurethane and heavy-build wire usually wind to same resistance and have the same inductance, and plain enamel is noticeably higher in resistance and inductance.

If you wind two identical coils, same resistance, but one with heavy-build insulation, the heavy build insulation coil will be noticeably brighter. It’s because there’s more capacitance going on since the actual metal in the wire has more gap between wires because it’s filled with heavier insulation. So, if that’s true then theoretically a looser coil would have the same effect. Moreover, polyurethane wire facilitates a punchier tone, while plain-enamel has a more vintage tonal character.

So, if other wire factors differ, you’ll have different behaviors. For example, if the coating has a different dielectric constant or thickness, the overall parasitic capacitance will change together with inductance, which shifts the resonant peak consequently. With loose windings or wire of same AWG but thicker insulation, you’ll have a lower inductance and parasitic capacitance, so even if the number of windings stays the same, the resonant peak will be higher and the output lower.

Pickup Cover Effects
Pickup cover types are another important aspect of tonal influence. Contrary to popular conception, it’s not so much whether you use covered or uncovered pickups that makes the most tonal difference. Nor, does the type of plating on a given cover make any considerable difference. Rather, what is most crucial to a pickup’s tone is two things: the exact metal or alloy a pickup cover is made of and the cover base thickness.

Solid-brass covers are usually the worst in terms of transparency and loss of high-end. Solid nickel-silver is the most transparent cover alloy, and it retains highs best. Yet, covers that are too thick (even nickel-silver) can impact tone as negatively as brass covers even. So, covers to avoid are brass, too thick nickel-silver and cheap alloys in general, as varying compositions of metal alloy effects tone differently.

Rating Pickups with DC Resistance
DC resistance is NOT a power rating, rather its the resistance of the wire in a pickup’s coil at zero hertz, something that only occurs when a guitar isn’t played. DC resistance specs are inadequate as sole power and tone indicators of an AC device like a pickup. Small fluctuating AC (not DC) voltages from pickups are what control outpout from an amp or plate currents of a tube. The large current flowing through the plate fluctuates with the same frequency as the small guitar pickup voltage, and the tones we love come through. An amplifier makes the small AC signal coming from your guitar pickups big enough to move a speaker cone.

If we do use DC resistance as a parameter for indicating tonal response, for one, we disregard the fact that this resistance rating is frequency dependant. Tonal output varies across the frequency spectrum. Additionally, the pure output rating of a pickup is more accurately indicated in millivolts. Millivolts could be a helpful parameter in indicating pickup output and tone if manufacturers agreed on a standard measuring method that provides such data measured at various frequencies over a wide frequency range.

Inductance is another important parameter to consider in the sonic evaluation of a pickup. Put in simplest terms, as a general rule the higher the inductance, the lower the treble response and the higher the output and midrange emphasis will be. For examples, a traditional Strat pickup has an inductance around 2.3 henry, while a Gibson PAF has an inductance around 4.4 henry, and some of the so-called “distortion” pickups have an inductance above 8.0 henry. With these comparisons, you get a basic idea of this quality.

So, several important factors can to be considered to more accurately speculate the tone and output of a pickup – tone and output depend mainly on the relation between magnetic strength, wiring resistance and the resulting inductance of a pickup. And, don’t forget the relation between the inductance of the pickup and the capacitance of guitar cables and effects. Guitar cable capacitance especially impacts frequency response and output.

Other Factors Influencing Pickup Tone
The electric guitar is still fundamentally an acoustic instrument. And, any given pickup responds very differently to each and every guitar model. The wood (or other materials) of a guitar absorbs some frequencies and resonates others. And, a pickup only picks up the frequencies and levels that a string is generating. So, for instance, if you have a guitar that absorbs frequencies most readily between 200 and 500 Hz, you will likely have thinner sounding treble strings, than if the guitar absorbed higher range frequencies. If your guitar resonated well between the previously mentioned frequencies, it would facilitate beefier treble string response. Additionally, guitars that are more resonant allow you to use a lower output, brighter pickup and still get the same volume.

Last but not least, it is every player’s unique articulation and musicality that ultimately impacts a listener’s perception of tone. As intangible as this aspect is, ranging from magical to mundane, every players unique touch is the most crucial factor influencing tonal perception. Not convinced? I ask you this then: How many of you have heard mediocre players playing through the finest “holy grail” gear, whether live or on the internet, only to be left unmoved by the tone. And, conversely, how many have listened recordings of brilliant players playing through something like a $50 battery-powered Pignose amp (as used on Derek and the Dominos’ Layla album, for instance), only to be left amazed at the tone achieved? I’ve experienced this phenomenom countless times – it is the magic alchemy of great Tone and musicianship.