Stacked pickups - I'm missing something

[big_teee]

Very nice transformation, Mark! I have another transformation, less appealing, perhaps, but leading to what I like to make: Start with a humbucker using slugs in both coils. Flip the coils outward so that the slugs touch the opposite narrow faces the magnet. Push the coils towards each other, compressing the magnet, until they are about 1/8" apart. Then erase all the magnet except the pieces between the slugs, leaving little cylinders that magically change to neo magnets. You can also wave a wand, and reduce the number of turns, leaving something you can tune as desired with a capacitor and amplify a bit either in the guitar or outside.

By doing that didn't you just make a Sidewinder?

[Mike Sulzer]

By doing that didn't you just make a Sidewinder?

Oh, forgot to "rotate the whole darn thing by 90 degrees so that it stands up instead of lying down", as Mark did. Please add that step into the Xformation.

[big_teee]

Oh, forgot to "rotate the whole darn thing by 90 degrees so that it stands up instead of lying down", as Mark did. Please add that step into the Xformation.

I like that better than bending magnets!
We all know magnet bending don't work unless they are rubber refrigerator magnets. lol
How about a blade, or slugs going thru both coils vertically, but have the magnets in the middle, like you do a P90.
Head to Head in the middle, both N/N, or S/S, instead of on the bottom.
I'm pretty sure I've seen that some where.

[Mike Sulzer]

I like that better than bending magnets!
We all know magnet bending don't work unless they are rubber refrigerator magnets. lol
How about a blade, or slugs going thru both coils vertically, but have the magnets in the middle, like you do a P90.
Head to Head in the middle, both N/N, or S/S, instead of on the bottom.
I'm pretty sure I've seen that some where.

That would work fine, although you would have to separate the coils a bit more than some designs, reducing the room for winding, or making the pickup deeper. Not a problem from my view since I like to keep the turns count down. The reason I like the "little magnets in the middle" is that it separates the cores of the two coils, replacing a high permeability connection with low. This tends to reduce the coupling a bit. Not a big deal, but it is always good to look for improvements

[Mark Hammer]

My point was basically that, like so many things in life, when you see them in a way you aren't expecting to see, they strike you as strange, rather than simply a slightly different version of what you already know. Heck, they might even look nonsensical and unfathomable. I can't begin to count the number of schematics I've tried to suss out that were drawn "wrong", and when I saw them drawn "properly", my immediate reaction was "Oh, one of those circuits! Why didn't I see that before?".

The manner in which the coils are oriented on a PAF style HB - side by side - distracts us from the reality that the magnetic structure underneath is essentially an extended bar magnet, just like Mike described, with one coil sitting on the northerly and, and the other sitting at the southerly end.

Naturally, there are oodles of important details that are different between stacked and PAF-type HBs, and worth considering and discussing. But fundamentally, they are both two relatively matched coils, one at each end of a magnetic gap, and wired in such a manner as to sense signal but reject hum.

FWIW, some 25 years or so back, I had a lengthy conversation with Rod Evans, of Evans Eliminator pickups, about an idea I had for a pickup, some of which involved a stacked humbucker. His verdict was that stacked HBs simply didn't cut it, and likely couldn't cut it. In his view, they simply could not nail "that sound". His own PUs were end-to-end HBs, not unlike the Novaks, and fit inside a Strat-sized cover, only his flatwork was sort of yin/yang configured, rather than mini-3-string pickups like the Novaks below.


As Big Teee quite correctly notes, one of the major differences between stacked HBs and PAF-style is that HBs that are stacked have the string essentially being sensed at one end of the sensing are, rather than across the entire sensing area as with a PAF. So while they don't function any differently, in a pure electronic sense, they certainly sound different, due to an assortment of factors like the sensing area thing.

[ReWind]

For gluing magnets, I use the runny CA, and a Hair dryer to speed things up.

Ever use CA accelerator? That stuff is great. Instant action.

[Joe Gwinn]

Really? Pickup patents? For example here is the fifth claim in Seth Lover's humbucker patent:

The claims are pure legalese, and are in effect defining a topology, to be able to lay a claim on all similar topologies, while avoiding collision with topologies already staked out. It is very hard to follow. More to the point, the technology is not described in the claims, so I would just skip them.

There is no magnetic return circuit in a humbucker. There are short high permeability pole pieces connected on the bottom by a much lower permeability Alnico magnet, which does little more than air. On the top it is essentially not connected at all. This is an example of a spurious claim. If the patent reader does not notice, it helps make the case that the patent has done yet one more useful thing; other than that it just sows confusion, not at all a bad goal for the inventor. No, do not read patents to attempt to understand how things work. You have to figure that out by, well, knowing how things work. Then you can see what a pile of nonsense many patents are. I have not seen a single pickup patent that did not contain significant errors. Most people, even those who should, do not understand magnetic circuits.

By definition, there is always a magnetic return circuit - magnetic lines always form loops, for lack of magnetic monopoles. In pickups, the return is through the air.

It's certainly true that there are errors in many patents, but patents are still the best and often the only available source.

It's also true that many inventors do not fully understand how their invention works, but the invention works nonetheless.

If you want to understand E&M, take a course, or at least read a decent text on your own and work some examples. You cannot learn E&M from reading pickup patents.

Red herring. The point is to understand how a particular pickup design works, not to learn E&M Field Theory.

I would venture that very few if any inventors of successful pickup designs know a shred of E&M theory, and yet life went on and music was made.

[Mike Sulzer]

The claims are pure legalese, and are in effect defining a topology, to be able to lay a claim on all similar topologies, while avoiding collision with topologies already staked out. It is very hard to follow. More to the point, the technology is not described in the claims, so I would just skip them.

I completely agree that they are legalese, and that is a significant roadblock to those with technical, but not legal, understanding, but
the claims must have support in the technology described later. Also, the entire patent is really legalese, and so you cannot ignore the claims because they are clues for decoding the confusingly presented information.

By definition, there is always a magnetic return circuit - magnetic lines always form loops, for lack of magnetic monopoles. In pickups, the return is through the air.

Yes, but I like to think of magnetic circuits without a significant practical return path as open, just as a battery with nothing connected to it is open. The difference between open and closed is not so large in the magnetic case, but it does count. The inductance increase caused by a steel pole piece in a pickup coil is only a few times, even if the pole piece permeability is high, while in a truly closed circuit such as a transformer core it would be much more.

It's certainly true that there are errors in many patents, but patents are still the best and often the only available source.

It's also true that many inventors do not fully understand how their invention works, but the invention works nonetheless.

Sure does.

Red herring. The point is to understand how a particular pickup design works, not to learn E&M Field Theory.

I would venture that very few if any inventors of successful pickup designs know a shred of E&M theory, and yet life went on and music was made.

Let's assume, as you say "The point is to understand how a particular pickup design works, not to learn E&M Field Theory." Your understanding of anything you read depends on your prior knowledge, both facts and concepts. Depending on the nature of the document and your level of knowledge, the information gained might be positive or negative. That is, it might just be confusing.

I never suggested that anyone would learn E&M theory from reading a patent. Quite to the contrary, I am saying you need some level of preexisting knowledge of E&M to understand the patent, that is, gain significant positive information.

I would guess that Seth Lover knew more than a shred of E&M theory. I do not think he got it working so well just from blindly copying what others had done.

[rjb]

There is no magnetic return circuit in a humbucker. There are short high permeability pole pieces connected on the bottom by a much lower permeability Alnico magnet, which does little more than air. On the top it is essentially not connected at all.

I may be reading too much into the patent text, but I think the claim implies that the string itself is part of the magnetic return circuit.
And the claim of increased efficiency doesn't mention the degree of increase....
Look at the sidewinder configuration in the patent- where the design is made way more complicated than "necessary" just to get those steel bobbin endpieces up near the strings. Whether correctly or not, Seth must have believed they served a useful purpose.
You say the pole piece tops are essentially not connected- but there is a difference between "essentially not connected" and "not connected".

At least Seth Lover presented some explanation for his design...

Unlike Bill Lawrence, who included this line in his patent for a sidewinder pickup:
Although it is not understood why this particular pickup construction works fantastically well,...

As Joe noted:
In either case, whether or not the science was 100% correct, the inventor gave enough information to duplicate the invention.

[Mike Sulzer]

That little bit of magnetic material in the string is a return path? Well, that is really stretching it!

But seriously, consistency must enter into this at some level. If the goal is to present enough information so that the invention can be duplicated, then the explanation should not contain things that have no essential importance in the operation. Patents are sometimes an ugly combination of too little and too much information. Thanks for the example from BL, but I think that if an inventor includes a line such as that, he really to prove that it does work fantastically well.

I may be reading too much into the patent text, but I think the claim implies that the string itself is part of the magnetic return circuit.
And the claim of increased efficiency doesn't mention the degree of increase....
Look at the sidewinder configuration in the patent- where the design is made way more complicated than "necessary" just to get those steel bobbin endpieces up near the strings. Whether correctly or not, Seth must have believed they served a useful purpose.
You say the pole piece tops are essentially not connected- but there is a difference between "essentially not connected" and "not connected".

At least Seth Lover presented some explanation for his design...

Unlike Bill Lawrence, who included this line in his patent for a sidewinder pickup:
Although it is not understood why this particular pickup construction works fantastically well,...

As Joe noted:
In either case, whether or not the science was 100% correct, the inventor gave enough information to duplicate the invention.

[Joe Gwinn]

But seriously, consistency must enter into this at some level. If the goal is to present enough information so that the invention can be duplicated, then the explanation should not contain things that have no essential importance in the operation. Patents are sometimes an ugly combination of too little and too much information. ... , but I think that if an inventor includes a line such as that, he really to prove that it does work fantastically well.

Patents are not scientific articles published in peer-reviewed journals.

Legally, one can patent something without having a clue how it works. It's sufficient that someone else can make it work following the teaching of the patent.

The claims are not part of the teaching. The claims are just that, in the same sense that a gold prospector went to the Land Office and claimed some land as containing gold to be mined. A claim is an assertion of a legal right, not an explanation of a scientific principle.

[Mike Sulzer]

Patents are not scientific articles published in peer-reviewed journals.

Legally, one can patent something without having a clue how it works. It's sufficient that someone else can make it work following the teaching of the patent.

Exactly right. As I have been saying, a patent is not a good place to learn about how a pickup works. Better off understanding E&M and taking apart a pickup of the type in question, looking and measuring as required.

The claims are not part of the teaching. The claims are just that, in the same sense that a gold prospector went to the Land Office and claimed some land as containing gold to be mined. A claim is an assertion of a legal right, not an explanation of a scientific principle.

Yes, as you say. But look again at Seth Lovers fifth claim:

Fifth, to provide a magnetic pickup having a metallic magnetic return circuit between a pole of the permanent magnet and a coacting string of a musical instrument to increase the strength of the magnetic field around the string and improve the efficiency of the permanent magnet.

It is not clear what legal territory he is staking out. The whole process, no matter how implemented, of providing a magnetic return circuit? Just his particular method for doing it? What is the significance of the fact that his method does not really do anything much?

[Joe Gwinn]

Yes, as you say. But look again at Seth Lovers fifth claim: ... It is not clear what legal territory he is staking out. The whole process, no matter how implemented, of providing a magnetic return circuit? Just his particular method for doing it? What is the significance of the fact that his method does not really do anything much?

You cannot read a patent claim as stating a scientific principle. Think of it as defining a topological filter that allows a non-technical judge to distinguish covered (inventor gets a legal monopoly) from not covered (either covered by some other patent, or public).

[chad h]

Thanks for these thought experiments, Mark and Mike. But, in many ways, they just amplify my confusion. I'll do my best to explain why.

Imagine we make two identical coils, with rod magnets in the cores. Ensure that the rods are oriented in the same way - may as well put them south-up. When oriented south up, imagine both coils from start to finish are wound clockwise. I can use these two to make a hum cancelling pickup in a bunch of ways.

1. Lay them side-by-side, but invert one (so its poles are now north-up, and start-to-finish the coil appears to be wound counterclockwise). Connect them in series, with the finish of the first connected to the start of the second. This is the standard humbucker.

2. Place one on-top of the other, but inverted. The south poles of one coil face up, and the south poles of the other coil face down. Also, viewed from above, one coil appears to be wound clockwise and the other is counter-clockwise. Unfortunately, the two sets of poles will repel each other. So we'll need some ferrous material between them to hold them in place. We can make this some sort of blade. Then we connect the finish of the first coil to the start of the second. Note, this is exactly the same arrangement as the standard humbucker above, except that the two coils are stacked rather than lying side-by-side. But notice the magnetic arrangement: the top magnets are north-up, and the bottom magnets are south-up. This pickup we turn on its side and call a side winder.

Importantly, the side winder is different from the stacked pickup, because in the stacked pickup we don't invert the top coil. Both magnets face the same direction, and start-to-finish, both coils still look like they're wound in the same direction. In order to get hum to cancel, though, we wire the end of the first coil to the end of the second coil.
Consequently, the pair of coils in the stacked pickup look just like the pair of coils in the sidewinder. But the difference between the two is that the stacked pickup has its magnetic cores pointing in the same direction, and the side winder has the magnetic cores pointing in opposing directions.

To me, this suggests that the sidewinder and the stacked magnet should give you completely different results, unless there's something I really don't understand about magnets. I'm presuming that if I take a pole magnet (south up) and place it on top of another pole magnet (south up) that I essentially get a single, tall pole magnet that is facing south up (just like the single bar magnets that run through the SD hot stacks). On the other hand, if I place a south-up pole magnet on top of a north-up pole magnet, I get a magnet that has north in the middle and south an either end. The magnet field is completely different.

As far as Mark's original thought experiment regarding the U-shaped magnet is concerned, I would point out that when you straightened the magnet out you will effectively invert one of the coils (relative to the strings and the other coil), so that (even though the wiring wouldn't change) the effective direction of one of the coils would reverse. Straightening out the U-shaped magnet would leave you with two coils wound in the same direction with magnetic cores that have the same direction. It wouldn't cancel hum at all.

[Mike Sulzer]

You cannot read a patent claim as stating a scientific principle. Think of it as defining a topological filter that allows a non-technical judge to distinguish covered (inventor gets a legal monopoly) from not covered (either covered by some other patent, or public).

Yes, I know. The question I was primarily addressing is what is intended to be covered and what is not? I do not see how anyone, technical or not, could determine what claim five intends to cover. Can you? The question of what the device actually does, and whether it does as claimed, is separate, but still of interest to me, of course.