Draft Chapter R – 3 Coils With 6 Humbucking Circuits

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Limited license for a book sale

This Chapter explains a type guitar pickup circuit disclosed in U.S. Patent 10,380,986 (Baker, 2019) and further developed in U.S. Patent 10,810,987 (Baker, 2020) and other patents.  Can you make one and try it out for yourself?  When a patent has been granted, each U.S. Patent states:  

“Therefor, this United States Patent grants to the person(s) having title to this patent the right to exclude others from making, using, offering for sale, or selling the invention throughout the United States of America or importing the invention into the United Stated of America, and if the invention is a process, the right to exclude others from using, offering for sale or selling throughout the United States of America, products made from that process, for the term set forth in 35 U.S.C. 154(a)(2) or (c)(1), subject to payment of maintenance fees as provided by 35 U.S.C. 41(b).”

As a practical matter, I doubt that anyone would license a patent until they had made one copy of the invention to see if it works, and if it is economical to make.  Patent law states that a patent must be written so that anyone “with ordinary skill in the art” can make the invention without undue expense in research and development.  So when I write a patent, I write it like an article in an engineering journal, complete with mathematical equations where necessary.  

So here’s the deal – I grant to any person who buys from me, or from any whom I assign to do business for me, one new copy of this book (estimated to be finished around the end of 2023) the right to make two circuits, as described below, without any onboard powered amplifier or electronics, for personal use in one or two of that person’s own guitars.  If the original owner of the book makes one or more for a third party, or offer one for sale to any third party, or sells one to any third party, that breaches this agreement and leaves any person responsible for such a breach open to a lawsuit which can take any profit or advantage gained by any such breach, and then some.  No one who buys any used copy of this book has any right to make, sell or offer for sale any circuit or invention covered by these and other U.S. patents granted to me.    

Licenses to manufacturing and commercial entities are another matter, and open to negotiation.  

The standard 5-way switch for 3 single-coil pickups

First, here is how an ordinary 5-way switch on a 3-coil electric guitar works: 


Fig. R.1

Fig. R.1 shows the connections for a standard 5-way switch in a electric guitar with 3 single-coil pickups, recast as a 3-pole, 5-throw switch (SW1 3P5T) to make the connections easier to see.  The pickups are Bridge with North-up poles (Bn), Middle with South-up poles (Ms) and Neck with North-up poles (Nn).  They have string signals +B, +M and +N.  Because the middle pickup has South-up (S-up) poles, the coil output connections must be reversed to provide a string signal with a phase consistently positive with the other two pickups.  But this reversed the hum signal (H), as shown in Fig. R.1.  Note that all three pickups have the “lower” terminals connected to ground, that triangular pattern of lines.  In this circuit diagram, wires that cross and have dots are connected at those dots.  There are no wires that cross in this diagram and are not connected are shown as a break in one line where they cross, to emphasize that they do not connect there.  Those are the conventions I use.  

The five-way switch is presented here as a 3P5T switch, with the poles shown as the arrows on the left, and the throws, labeled 1 to 5 above, shown as circles with which the poles make contact for each throw.  Here, only the coils, switch, ground and output (a circle surrounded by a ground) are shown; the pots and capacitors for the volume and tone controls are ignored and left out.  The circle surround by a ground (note the broken line of the outer circle) commonly means a jack.  The output signals for each throw are presented below the switch diagram.  Throws 1 to 5, respectively, put string signals for B, (B+M)/2, M, (M+N)/2, and N to the output.  If the pickups have reasonably similar electrical and magnetic characteristics, then Throws 1 to 5, respectively, also put hum signals on the output: H, (H-H)/2 = 0, H, (H-H)/2 = 0, and H.  So Throws 2 and 4 are nominally humbucking.  Note that if the hum signals had been the same phase for Throws 2 and 4, both outputs would be (H+H)/2 = H.  That is a characteristic of two pickups connected in parallel.  

The humbucking 6-way, 3-coil circuit 

Fig. R.2

Now consider the 6-way humbucking circuit in Fig. R.2, using the same 3 single-coil pickups, again ignoring the tone and volume circuits.  The pickups are disconnected from ground, the middle pickup terminals are reversed from those in Fig. R.1, and the same hum phases from each pickup terminal (-H) are connected together a the common connection point, as designated by the triangle with a C inside.  Switch 2 is a 3-pole, 6-throw switch which connects one pickup to ground (low output) and one or two pickups to the (high) output.  If all the pickups are reasonably equal in electrical and magnetic characteristics, so that the hum signal from each is the same, then every output has hum equivalent to H – H = 0.  The resulting output string signals for switch throws 1 to 6, respectively are: 

B-N;  (N-M)/2-B;  (B-M)/2-N;  -(M+B);  N+M;  and  (N+B)/2+M

This is the approximate order of tones from bright to warm (for 3 P-90 pickups in a previous prototype), which may change with the pickups and instrument.  If the common connection point (triangle-C) is shorted to the ground, then the last term in each expression (-N, -B, -N, -B, M, M) is lost, and so is humbucking.  One gets outputs with hum:

B;  (N-M)/2;  (B-M)/2;  -M;  N;  and  (N+B)/2

There is no guarantee that these will have an order of tone that simply increases or decreases in brightness.  They will be mixed.  For a mechanically-switched system, one can only choose the order of tone for either one of hum or humbucking outputs, but not both.  But adding a shorting switch does add more tones.  

As a practical matter, it may be hard to tell the difference between a couple of the humbucking tones, leaving just 5 that are audibly different.  Or it could just be the tin and tinnitus in my ears.  Affordable mechanical switches suitable for this circuit are either the 4P6T rotary switch or the 4P5T lever superswitch.  In a commercial Strat-type guitar, either one will often require more room in the electronics cavity under the pick guard that is usually provided.  The standard 5-way lever switch on a 3-coil guitar often drops into a deeper hole cut in the bottom of the electronics cavity.  To modify an existing guitar could mean routing or chiseling out a larger hole in the bottom of the cavity to accommodate the larger rotary or superswitch.  This prototype guitar with a skeleton body and front and back covers does not have that problem.  


Fig. R.3  4P6T Rotary Switch Fig.

R.4  4P5T LEVER Switch

Figs. R.3 and R.4 show a 4P6T rotary switch and a 4P5T lever superswitch, respectively.  The labels Px refer to the pole solder lugs, and Tx to the throw solder lugs.  In Fig. R.3, P4 just barely shows and its associated throws do not.  The throw labels for P3 on the lower wafer in Fig. R.3, in the lower half of the figure, have lines showing the associated positions of the same throws for P1 on the upper wafer.   In Fig. R.4, only the top of two wafers show clearly, with poles P1 & P2, and their associated throws, T1 to T5.  The second wafer, with P3 & P4 are obscured by the first.  Since a lever switch in an electric guitar is typically mounted as far from the strings as possible, the wafer showing in Fig. R.4 would typically be on the string side of the switch, convenient to the test of the electronic circuit.    

Fig. R.5

Fig. R.6

It’s relatively simple to convert the circuit diagram in Fig. R.2 to connections on the switch in Fig. R.3, as shown in Fig. R.5.  The circuit only has three inputs of string signal, B, -M and N, and two outputs, the high and low (ground).  Let the poles and inputs be P1 <—> -M, P2 <—> B, and P3 <—> N, and indicate the outputs by Blue for high and Red for ground.  When I first did this, I redrew Fig. R.2 twice again, first to find the shortest wire connections between throw solder lugs on Fig. R.2, then again to make the throws look more like the actual switch.  But it can be much simpler and more direct than that.  

One can simply mark the tops of the solder lugs for T1 to T5 with red and blue felt pens.  In Fig. R.5, all the throw lugs for the B, -M and N string signals are marked with either blue or red dots, according to Fig. R.2.  Connect the blue dots together with blue lines, and the red dots together with red lines, and that’s where the high and low output wires go.  Fig. R.6 shows how this has been done with 28 gauge solid magnet wire.  Magnet wire doesn’t need stripping.  The heat of the solder melts the insulation off at the joint.  Simply don’t let the wires touch each other, so if the heat travels far enough the wires don’t short together.   

Figs. R.5 and R.6 show two red (low) wires and one blue (high) wire going to other parts of the circuit for a previous prototype using three Allparts Vintage Chrome Humbucker pickups with the same switching order as Fig. R.2.  Any pole connections and soldered wire pattern that will satisfy the circuit diagram will work.  There is more than one, and others may use less wire.  

Comments on single-coil pickups for humbucking circuits

There are several essential and desired characteristics for single-coil guitar pickups to be used in this kind of circuit:

  1. Essential:  Two-wire shielded output, with insulation colors coded to indicate hum phases first and string signal phases second.  For example, white and black for North-up poles, with black being the nominal negative hum phase, and red and green for South-up poles, with green being the nominal negative hum phase.  
  2. Desired:  Nominal negative hum phases are designed to be connected to the common connection point, and should be the outer windings of the pickup coil.  The common connection point could be connected to ground through a low-value capacitor to short out the interference frequencies higher than audio.  
  3. Desired:  Output connectors.
  4. Desired:  The magnetic direction of poles easily reversible without special tools.
  5. Desired:  Coil electrostatic shielding with interruptions to avoid hysteresis currents due to string signals.
  6. Desired:  Ferro-magnetic poles easily replaceable with different pole shapes, heights and configurations, without special tools.
  7. Desired:  Modular single-coil pickups, conforming to U.S. Patent 10,991,353 (Baker, 2021).  

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New page with U.S. Patents for licensing

The following U.S. Patents are available for licensing. Click Here for the index page, and click on the links below to reach each patent. They have all been modified upgraded from the standard uspto.gov download to include drawings and properly formatted equations and tables.

U.S. 9,401,134, Baker, 2016 – Acoustic-electric stringed instrument with improved body, electric pickup placement, pickup switching and electronic circuit

Abstract – An electric-acoustic stringed instrument has a removable, adjustable and acoustic artwork top with a decorative bridge and tailpiece; a mounting system for electric string vibration pickups that allows five degrees of freedom in placement and orientation of each pickup anyplace between the neck and bridge; a pickup switching system that provides K*(K-1)/2 series-connected and K*(K-1)/2 parallel-connected humbucking circuits for K matched single-coil pickups; and an on-board preamplifier and distortion circuit, running for over 100 hours on two AA cells, that provides control over second-and third-harmonic distortion. The switched pickups, and up to M=12 switched tone capacitors provide up to M*K*(K-1) tonal options, plus a linear combination of linear, near second-harmonic and near-third harmonic signals, preamp settings, and possible additional vibration sensors in or on the acoustic top.

U.S. 10,217,450, Baker, 2019 – Humbucking switching arrangements and methods for stringed instrument pickups

Abstract – This invention develops the math and topology necessary to determine the potential number of tonally distinct connections of sensors, musical vibration sensors in particular. It claims the methods and sensor topological circuit combinations, including phase reversals from inverting sensor connections, up to any arbitrary number of sensors, excepting those already patented or in use. It distinguishes which of those sensor topological circuit combinations are humbucking for electromagnetic pickups. It presents a micro-controller system driving a crosspoint switch, with a simplified human interface, which allows a shift from bright to warm tones and back, particularly for humbucking outputs, without the user needing to know which pickups are used in what combinations. It suggests the limits of mechanical switches and develops a pickup switching system for dual-coil humbucking pickups.

U.S. 10,380,986, Baker, 2019 – Means and methods for switching odd and even numbers of matched pickups to produce all humbucking tones

Abstract – This invention discloses a switching system for any odd or even number of two or more matched vibrations sensors, such that all possible circuits of such sensors that can be produced by the system are humbucking, rejecting external interferences signals. The sensors must be matched, especially with respect to response to external hum and internal impedance, and be capable of being made or arranged so that the responses of individual sensors to vibration can be inverted, compared to another matched sensor, placed in the same physical position, while the interference signal is not. Such that for 2, 3, 4, 5, 6, 7 and 8 sensors, there exist 1, 6, 25, 90, 301, 966 and 3025 unique humbucking circuits, respectively, with signal outputs that can be either single-ended or differential. Embodiments of switching systems include electro-mechanical switches, programmable switches, solid-state digital-analog switches, and micro-controller driven solid state switches using time-series to spectral-series transforms to pick the order of tones from bright to warm and back.

U.S. 10,810,987, Baker, 2020 – More embodiments for common-point pickup circuits in musical instruments

Abstract – This invention refines and expands the use of mode switches in common-point connection circuits for matched pickups on musical instruments. For example, on a 3-coil S-type electric guitar, where the common-point connection circuit with a single-ended output provides three humbucking pair outputs and three humbucking triple outputs, a 4P2T mode switch can ground the common point and provide both all of the standard non-humbucking 5-way switch outputs, as well as adjusting the tone capacitor to make both humbucking and non-humbucking tone outputs more compatible. On an electric guitar with three dual-coil humbuckers, mode switches of one 6P2T, one 2P2T and three 1P2T can choose between dual-coil and single-coil operation modes, humbucking and non-humbucking modes, and partially simulate the effect of flipping single-coil magnets at will, by choosing which coil of each humbucker is used.

U.S. 10,847,131, Baker, 2020 – Modifications to a lipstick-style pickup housing and core to allow signal phase reversals in humbucking circuits

Abstract – This invention discloses a pickup based upon the core of a common lipstick pickup for an electric stringed musical instrument with a core and housing, the core comprised of a magnet, coil form, and a wire coil connected to electrical contacts on the coil form, and a separate housing providing mounting to the body of the instrument and mating electrical contacts for that core, such that the core can be removed from the housing, flipped so as to reverse the magnetic field towards the strings, and reinserted into the housing, such that any humbucking circuit constructed with other matching pickups will remain humbucking.

U.S. 10,878,785, Baker, 2020 – Stringed instrument pick holder with adaptation to pick guard

Abstract – This invention uses a simple, decorative and effective way to hold picks to a guitar body, especially a solid electric guitar body or the head of a neck. It comprises a flat plate, which can be conveniently included in the design of a pick guard, using at least one mounting screw, one or more fingers to hold down individual picks, each tensioned by separate screw, and a thin shield under the pick holder to keep each pick from rubbing on the body finish. The parts can be cut, carved or printed to decorative designs.

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Eulogy for Adobe PhotoShop 7 ™

Thanks to Microsoft, most likely, PS7 is getting Alzheimer’s. It no longer remembers to stroke the entire path on command, leaving sections undone. Why? Probably because I used Windows Update on Windows 7.

I recently upgraded my connection from a mobile hotspot to cable internet, so that the Windows updates wouldn’t kill off my $10/GB metered data. After hundreds of megabytes of updates, my Windows 10 laptop now boots and comes out of hibernation slower than ever, and PhotoShop 7 on my Windows 7 desktop is losing capability.

I shall mourn PhotoShop 7. Its classic toolset is so perfectly made that I’ve learned to use it for photos, paintings, graphic art, CAD drawings and electronic circuit diagrams ever since it was Version 4. For example, I used it to take a pencil drawing like this:

(c) Don Baker 2010

and turn it into this:

(c) Don Baker circa 2011-12

I used it for all the figures of guitar bodies, electronic circuits and graphs in U.S. Patent 9401134 B2: https://patents.google.com/patent/US9401134B2/en

Until now, I have not needed anything else. I’m currently using it for patent applications and to write a new textbook on guitar electronics. That has now become more difficult and uncertain.

Microsoft is like a Developer enthusiastically putting up ever-higher and more expensive condos, without bothering to notice the endangered flowers and butterflies it tramples underneath. Never bothering to fix the old bugs as it compulsively adds every more bloated “features”. Creating millions upon millions of lines of octopus-code, all the while installing new bugs. It doesn’t really care how much it damages the work of others, so long as it can induce us to buy more products. Whether we can afford them or not.

If Karma accrues, sooner or later, these turkeys will have to live on Social Security and minuscule COLAs, while their medical insurance continues to rise above that pace. One can only hope.

© 2018 Don Baker dba android originals LC, Ph.D retired

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New U.S. Patent filed & background published

Yesterday, I filed my 3rd Non-Provisional Patent Application, and today published the background theory for it at: https://www.researchgate.net/publication/323686205_Making_Guitars_with_Multiple_Tonal_Characters   The patent involves matched, single-coil pickups for humbucking circuits with reversible magnetic poles.

I have a new area for publications of papers like this on ResearchGate.Net.  There are 2 so far.  You can find them at: https://www.researchgate.net/lab/Donald-L-Baker-Lab


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Banning Users

The majority of new users who sign up turn out to be listed as spammers on CleanTalk.org.  From now on, those new users will not only be deleted, their domains will be banned.  Why do they even bother?

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On the Topologies of Guitar Pickup Circuits

How do you get 620 potentially unique guitar tones from 4 single-coil pickups, or 310 from 3 humbuckers?

Read here: https://www.researchgate.net/publication/323390784_On_the_Topologies_of_Guitar_Pickup_Circuits

Abstract: Many of the U.S. patents involving switching circuits for electric guitar pickups have failed in the marketplace because they do not show the topologies generated by switching configuration, and thus fail to eliminate duplicate circuits and circuits with null outputs. Series-parallel circuit topologies of any complexity, with potentially unique tones, can be generated from small to complex by simple rules, as can the number of ways to switch pickups around in a particular topology, and to reverse individual pickup connections to change the phase of their contribution to the output. But the audio separation of “potentially unique” tones have to be verified by spectral measurements. This affects both single-coil and dual-coil humbucking electromagnetic string vibrations pickups, as well as other types of sensors.

This is just the beginning

(c) 2018 Don Baker  dba  android originals LC

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The Walkin Squawkin Patent Examiner Blues – Part 1

I got this in an e-mail from my U.S. Patent Office Patent Examiner on Jan 24th, 2018:

“I cannot conceive of any way to generate an “infinite” (your word) table that would accommodate the breadth of claim 28. You mentioned going through this and “visually” deleting duplicates. How do you do that with infinite pickups? How do you do it with 500,00 pickups? 10,000? 500? You mention FFT, claim 28 is silent as to any FFT. Or, how do you create a table-lookup system to delete duplicates of, say, 500,000,000 pickups? 10,000? 500? Even 25? And finally, to me, removing duplicates is pretty obvious, e.g., to optimize user experience, to reduce CPU load, minimize memory/storage, etc. I just did a quick search of “eliminate duplicates” and returned about 14,000 hits.”

Speaking of “obvious”, I got this from Google today:

Can you say “super obvious”?

There’s a mathematical object, with which some Patent Examiners may not be familiar, called an “infinite series”. It doesn’t mean that you have to take it all the way to infinity, just that in principle it can be taken that far, according to some relatively simple rule.

I have a relatively simple set of rules for expanding pickup (and other sensor) circuit topologies from a single pickup, to a series and parallel pair, up to any number and complexity of series-parallel circuits you might wish. To cover all the cases, these rules happen to generate a number of duplicate circuit topologies that have to be eliminated, before counting up how many different ways you can get potentially unique tones from those pickup circuits. For small number, you just look at them and ask, “Which one of these is like one of the others?”

Simple, but most inventors who have filed pickup circuit patents haven’t bothered even to draw out the circuits their switching systems produce. Consequently, their patented switching circuits often have a number of duplicate circuits, producing duplicate tones. And even a number of circuits producing no output at all.

This goes all the way back to the Fender Marauder patent, US3290424, C.L. Fender, 1966. Four 3-throw switches gave it 81 different parallel-circuit switch configurations, of which one had no output. About half of the rest are duplicate circuits with duplicate tones, simple because of you reverse the output connections of a pickup circuit, the human ear cannot tell difference without any other reference. And of the unique tones, only a small fraction could have been humbucking.

The Marauder allegedly failed in the marketplace for being too noisy. Not to mention 81 switch positions with no map to the tones and duplicate tones.

So I systematically went about determining just how many unique series-parallel connections you could get from J number of pickups, how many unique ways you could switch pickups from one spot in the circuit to another, and how many unique ways you could reverse the connections of one or more pickups in the circuit to get a new tone. The number of unique topologies for J pickups don’t seem to have an equation, but number of ways you can switch pickup positions and reverse connections do.

So, how do you figure this out for “500,000 pickups?” Can you say “computer”?

Claiming, “I cannot conceive of any way to generate”, is like saying that because it is difficult to add 3000 10-digit numbers, that one must throw out the principles and methods to add 2 4-digit numbers. And besides that, the claim involving FFTs was past where this gentleman had bothered to read, in the second independent claim set.

And last, but not least, no matter how many unique circuits and tones you may devise, they are not truly unique until they are proven unique with actual spectral measurements. Because as the Great Murphy can tell you from his Law, if two tones can be very close together as to be virtually indistinguishable, they will be. You just don’t know which ones or how many. And that children, is why we say “potentially unique”.

It seems than an engineer has much less problem with this fact of nature and life than at least one U.S. Patent Examiner.

(c) 2018 Don Baker   dba   android originals LC

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Why guitar pickup switching patents fail in the marketplace

I’ve reviewed some more guitar pickups switching patents lately, and most if not all of the ones I’ve seen suffer design flaws that generally cause them to fail in the marketplace, for some of the following reasons:

  1. They almost never show in the Figures all the circuit topologies that the switching configurations produce, and thus never discover all the duplicate circuits and circuits with null outputs. This often leaves the user with a lot of switch combinations that produce exactly the same tones, or no tones at all.
  2. They don’t acknowledge that the human ear cannot tell the difference between a signal and its inverse phase, without a separate reference. Thus the signals like N B and –N+B are often wrongfully counted as separate tones.
  3. They don’t acknowledge that the coils of humbuckers are so physically close together (about the 16th to 32nd harmonic) that, even if they produced separate signals, they produce virtually the same signal. Never mind that they share the same magnetic circuit and are magnetically coupled, like an audio transformer. I have even used a HB with a signal generator as an audio transformer to test a preamp circuit. Not very efficient, but it produced a signal. So often every combination of one coil each from 2 humbuckers is wrongly counted as a separate tone, ignoring duplicates. Not counting any series and parallel combinations, 2 humbuckers produce exactly 2 single-coil tones (N and B), 2 humbucker tones (NN and BB), and two 4-coil tones, (NN+BB and NN-BB). Out-of-phase combinations in the same humbucker, like Nn-Ns or Bn-Bs, where n and s are the north-up and south-up coils of the humbuckers, produce virtually null signals.
  4. They don’t acknowledge that the only tonal difference between a series and parallel combination of two pickups or coils comes from the interaction with the load, namely the tone pot circuit and the volume pot, and the guitar cable and amp input. A lower impedance load causes the higher-frequency tones to roll off at a lower frequency than a higher impedance load. So when a pickup or coil feeds directly into a preamp that has a fixed impedance, there is no difference in tone unless the series-parallel switching is done before the preamp. And if the preamp has a very high-impedance input, then tonal difference between series and parallel pickup coils switched before the preamp will be well above human hearing.
  5. They don’t verify, by any kind of spectral measurement, that all the switch combinations actually produce audibly separate tones. They often falsely assume, without measurement and verification, that every different switch combination must produce a different tone, the more the better. Then, without ever having mapped what tones go with what switch combinations, they leave it all to the user to figure out. Then, to all that complexity producing such small results, they add the cost of more electronic parts.
  6. And has anybody seen a guitar with digital signal processing sweep the market?

Small wonder that the 3-way and 5-way switches are still so popular, and make up the bulk of the market, even if they are 50 years or more old.

© 2018 Don Baker dba android originals LC, Ph.D retired

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