How pickups work, magnetism, and other inflammatory information

[Ritchie200]

In regards to the Guitar Case Amplifier thread, I got to wondering how having a speaker magnet right next to the guitar might be detrimental. My gooogely research took me to several heated discussions about how pickups actually work.  The premise being that we lemming no nothing guitar players believe the string disturbs the magnetic flux lines and that's what gives us our signal.  When in reality, the magnets in the pickups magnetize the strings and that movement above the pole pieces gives us our signal.  Yet others claim that the signal is the same, is a combination of both, is not a factor since it is in the same North or South field orientation, if so why do pickups sound different, more pickups deaden strings, soap bar pickup magnets are too strong, humbuckers cancel out magnetic fields being adjacent, how come I can yell into my pickup with no strings and can hear it amplified, people claiming to be magnetic physicists (?) and PhD's ended up doing battle! 


In the end I really didn't learn a thing and like religion and politics, the thread just ended.


Any thoughts?


Jim

[SILVERGUN]

Any thoughts?

Yes
Read more:
https://www.seymourduncan.com/support-pickups-101/getting-started

Damnit.....I couldn't just tell you to read more and not read more myself.
I enjoyed this from Seth Lover:
“…...the magnetic field comes up to the stings there and magnetizes the strings. That’s one of the things that most people don’t understand. They figure that string is waving there and cutting the magnetic lines of force. Nuts. That isn’t it. The magnet, all it does is magnetize the string. Now you’ve got a waving magnetic field. And we have a fixed coil with a waving magnetic field to induce voltage. If you want to, take the magnet out. One you’ve magnetized your strings, it will play until the string loses it. Players think the string, the magnetic field from the magnet comes up to the string and by twisting the magnetic flux back and forth that’s what induces the voltage. That’s not what happens."

[jjasilli]

Until this thread I always thought it was exactly what Seth Lover says it isn't!  Because:


When a conductor is placed in a changing magnetic field, the electrons in the conductor move, generating an electric current. Magnets produce such magnetic fields and can be used in various configurations to generate electricity. Depending on the kind of magnet used, a rotating electric generator can have magnets placed in different locations and can generate electricity in different ways. Most of the electricity in use comes from generators that use magnetic fields to produce that electricity.  https://sciencing.com/magnets-used-generate-electricity-6665499.html


I now believe that the magnetization of the el guitar string is important. Otherwise, bronze (non-magnetic conductor) wound acoustic guitar strings would work as well nickel (a magnetic conductor) wound strings; but they don't.

[Williamblake]

Understanding pickups wrong or right , there is only so much you can mess up i am thinking, yet. Adjust the wrong hight. Using coil split shorting a coil instead of leaving the unused coil open. What else could go wrong?

[PRR]

> cutting the magnetic lines of force.

That's the explanation of conventional generators. Moving conductor cuts the lines of magnetic force which induces a voltage in the conductor.

We don't take voltage from the string! We could, but the voltage would be super low and it would pick up much crap.

I'm not even sure the string "holds" magnetism. Can someone quick slip the magnet out while string is ringing and see if output persists? I suspect big drop-off. Does not matter since we leave the magnets near the strings so they are constantly magnetized.

[shooter]

I'm not even sure the string "holds" magnetism.

no secret knowledge but would agree, any residual would be a rounding error in any guitar application.  can always cut the string fast n see if it sticks to the fridge 

never thought deep about MRI     sooo...

my understanding, you have a static field, you wave steel around and sample the variation from static field   

[Ritchie200]

So, as Peter Pan would say, "Here we go!!!"

I also read the Seth Lover bit and the SD info.  Yet there are those who dispute Lover.  Some say metal filings stick to the pickups and not the strings so any supposed magnetism is minute and inconsequential.  The bronze string thing came up too but it is bronze wrap over a steel core.  Then the argument about only steel or "magnetizable" materials can only produce a signal in a magnetic field.  Until someone brought up the back voltage generated by a copper wound speaker voice coil coming back to rest from an excursion.

Jim

[PRR]

It's all relative. You can move the conductor. You can move an iron armature. You can move the magnet.

Most loudspeakers are moving conductor. There are moving armature speakers for special applications. Usually the magnet is too heavy to be vibrated rapidly.

[SILVERGUN]

>I'm not even sure the string "holds" magnetism. Can someone quick slip the magnet out while string is ringing and see if output persists? I suspect big drop-off. Does not matter since we leave the magnets near the strings so they are constantly magnetized.

From the same article I got the Seth Lover quote: https://www.guitarworld.com/gear/how-does-a-guitar-pickup-really-work
This guys says he tried a similar experiment:
.... Let’s do an experiment to find out. We built a Zexcoil pickup, complete with everything but magnets. It still has the coils, ferromagnetic pole pieces and structural elements, just no magnets and no magnetic field of its own. We take this no magnet pickup and we suspend it above the guitar, so that it is the same distance from the strings as the magnetized pickup installed in the guitar. Then we switch between them.

What do you think happens?.....(edited out fluff)

....Surprise! Much of what you thought you knew about how pickups work is wrong, or at least incomplete. The pickup with no magnet sounds exactly like the pickup with a magnet. Pickups do not need a magnet at all, they only need a magnetized string! Now of course the easiest way to magnetize the string practically is to incorporate a magnet into the pickup, so that’s why we do it that way.

[PRR]

> We take this no magnet pickup and we suspend it above the guitar

In the video, the no-mag pup is mounted above a standard with-magnets pup. So it HAS a magnet, just mounted separately.

The three pieces (coil, magnet, armature/string) can be mounted in many different configurations. Just like engines can be built overhead or side valves, cams, pistons vertical diagonal flat and radial. It is a prolific field for patents.

The pre-WWII magnets had so little flux for their size they were often mounted oddly ("frying pan").

Obviously we put the magnet "in" the pup because it is slightly thriftier of magnet flux, because it makes a one-piece unit for easy mounting, and putting bits above the strings is more awkward. (This was done on some very early pups which have faded from the market.)

[jjasilli]

See:  https://education.jlab.org/qa/electromagnet_is.html


In this context a magnetic field is required.  The magnetic field can be produced by a permanent magnet.  Alternatively, an electromagnet can be used; but this requires a power source.  Electric current flowing through a copper (non-magnetic) coil produces a magnetic field.  The strength of this filed can be increased by using a ferrous (magnetic) core material, per the above article.  The point is that ferrous conductors are much more efficient than non-ferrous conductors in voltage generation.


Back to PU's -- a ferrous guitar string (iron compound, and/or nickel) works better at generating a signal voltage, than does a non-ferrous conductor, such as copper or bronze.  A non-conductor, such as a nylon string, moving in a magnetic, field accomplishes nothing.  I'm now thinking:  the fact that a ferrous conductor, the most efficient material at voltage generation, also becomes magnetized (at least temporarily) in the presence of the magnetic field, is a necessary truth, but may be irrelevant. 

[SILVERGUN]

Jimbo, maybe this is too simple but hey so am I....this is how I see this part of your initial question:

>how come I can yell into my pickup with no strings and can hear it amplified
because your pickup is a transducer and your voice is voltage(emf) at a certain frequency.

Notice how much harder you have to yell to get your voice to amplify through your guitar. Way louder than the unamplified electric guitar string. Your non-magnetized voice has to work that much harder to create the emf needed to induce voltage into the coil.

Magnetizing the strings and "picking up" emf is just a way more efficient way of inducing that voltage into the coil.

[sluckey]

It's guitar dependant. Merle didn't even need a mic. Just sing into his Tele.

[Ritchie200]

Exactly my thought jjasilli - irrelevant. 

HOWEVER...  If that was the case, why don't we spin coils of ferrous wire along with our steel laminations in a magnetic field to produce our electricity?  If ferrous materials cause the greatest disturbance in the force (Luke, see what I did there?), why use copper?  Especially since copper actually produces a counter magnetic field that would be detrimental to the process.  Do we loose that much in conductivity and heat to make a lesser disturbing material (copper) still the most efficient?  You would think some alloy of wire could be made with ferrous-like disturbing properties?  Or does this just go on to prove our "irrelevant" assumption?  It seems bits and pieces of Faraday are being applied as needed to prove one view or another!

Yeah, the open coil directly above the magnetic pup proves nothing.  I thought that was a silly test because essentially nothing in the "environment" has changed, only the detector.

SG, Unless I am taking massive doses of iron supplements, I doubt my bad breath has much EMF.  However, we did used to scream, "I AM IRONMAN!" into our guitars to replicate Ozzie's introduction to the song!  But that was with strings....

Jim

[shooter]

You would think some alloy of wire could be made with ferrous-like disturbing properties?

we have the technology 

https://en.wikipedia.org/wiki/Superconducting_wire

[jjasilli]

I'm not saying anything definitive about PU function.  Just thinking out loud as part of this conversation.


Anyway, Iron is not a good el conductor, so it's not used for that purpose. See:  https://www.quora.com/Can-iron-conduct-electricity  Gold & silver are the best el conductors, but very expensive.  Copper is nearly as good, and much cheaper.  Copper is a far better el conductor than iron.  So, copper is the usual choice for a conductor.  For electro-magnetic purposes, iron is best for magnetic fields - even if the magnetic field is generated by a copper coil.  (Hey, no bootleggin' 'round here!)


N.B.: the fact that Seth Lover subscribes to a theory does not make it true. This is a fallacy of reasoning called "The Appeal to Authority".  History has lots of examples of great inventors who turned out to have theory wrong. Positive vs. negative electron flow comes to mind.  Still great work & advancements were made.

[jjasilli]

Geez, I'm back in Seth Lover's camp.  See:  https://www.youtube.com/watch?v=TKNZGX_Za7M


A magnet needs to move near a coil in order to generate a voltage.  For an el guitar, the only thing moving is the string.  Therefore, the string must be the moving magnet. 

[Ritchie200]

Armature windings are not a magnet nor is it magnetic, yet it produces EMF as it interacts with the magnetic field. 

Come on JJ, don't bail on me now!

Jim

[PRR]

> The point is that ferrous conductors are much more efficient than non-ferrous conductors in voltage generation.

No, iron conducts the magnetism. (Nickle too but much less well, and costs more, and is hard to form.)

Iron is *rarely* used as a conductor, in places where strength is the #1 issue. My neighbor gets power through the woods at 20,000V on iron wire. A house, at that voltage, wet spaghetti would carry the electric load; but wind blows and branches fall and you really want the 20KV wire to stay up.

> Gold & silver are the best el conductors, but very expensive.  Copper is nearly as good, and much cheaper

For *size* silver is best of all, copper is very near-as-good and far cheaper.

Aluminum is best for weight and cost.

Gold isn't in the running with these. We use Gold on low-power contact surfaces, thinly, because it doesn't tarnish.

[Ed_Chambley]

If you get a chance to change magnets in pickups, different gauge wire, and combinations you will find any pickup will sound good.  Actually, if you adjust your pickups high, you will hear a pulse like tremolo. Strings too magnetized for string height. Lowering the pickups until this pulse cannot be heard through the amp is one solution. It simply reduces magnetism from the strings and therefore produces less signal, but will vibrate longer and wider.  Result from doing this very in many ways, but IMO it is how a pickup height should be. So you lower and the sound gets fatter, but now not as articulate. You are using a5 magnets, 43 enamel copper wound. Change to alnico 2 magnets that contain no cobalt and increase your amount of windings reduces magnetism.


I have never considered strings a magnet and can assure you if you remove the pickup magnet, it cannot work! Also, some guys really like old pickups or certain ones.  When they lose some magnetism they naturally have lower output and seem thicker sounding.  I am not sure, but I think Seth Lover was simply trying to make a p90 humbucking and shielding technique.  He at the time couldn't have known what a humbucker should sound like.


Now consider string metals and that old pickup. Put some cobalt strings on it and the sound will be louder and cleaner.


What makes more output? An a5 loaded humbucker with a DCR of 11 or a2 magnet with DCR of 18? Same conditions?


I can assure you building pickups without magnets or not experimenting with different types of magnets it is just dumb luck if you get what sound you want. Since fender single coils are easy to change individual, push out the magnets under string 6, 4 and  2 and flip them over. See what happens.

[jjasilli]

Armature windings are not a magnet nor is it magnetic, yet it produces EMF as it interacts with the magnetic field. 

Come on JJ, don't bail on me now!

Jim

No single "It" produces the EMF.  The EMF results from a combination of 3 things, all of which must be present together at the same time in close proximity: 1. a magnet (magnetic field) - this requires a ferrous material; 2. an el conductive coil (usually copper for reasons stated above); 3. motion.
 
Your choice:  you can move the coil (armature), or the magnet.  This does not change the analysis. 


(This is appropriate to a passive PU.  A magnetic filed can also be generated, even w/o ferrous material, by running electricity though, say, a copper coil; but this requires a power source.  This tends to muddy the topic w/o shedding any light on the matter.)

[SILVERGUN]

I bailed cause I'm smart enough to know when I'm over my head but just for the record, I was stretching the definition of (emf) as Electromotive Force

Not to be confused with Electromagnetic Field as (emf)

[shooter]

fun reading on specs n limits, didn't find guitar pickups 

https://www.icnirp.org/cms/upload/publications/ICNIRPemfgdl.pdf

[Ritchie200]

Well that was some light reading!!!!


So per Ed’s comment, I don’t think the discussion is about whether or not we need a magnet. It’s about how the magnetic field is tickled for our signal. A pickup too high has the string deep in the strong lines of force. We lower the pickup and are moving out into the weaker lines. Is the output proportional to the string’s magnetism? Or is it just geography?  If the magnetism of the string is the driving force (so to speak), strings would be ruined if brought too close to a pickup (pickup high). Yet we adjust the pickup down and it sounds just fine. What happened to the uber magnetism of the string? 


I agree something has to move to create a signal, but what is being claimed is you need two magnetic things to make that happen. I just dug out some old strings changed out just a few days ago and drug them through some metal filings on my mill. Guess what? Nothing stuck. I still think that a ferrous material is needed to disturb the lines of force in a magnet for the coil to pick up.  Any residual magnetism in the ferrous material by being exposed to the magnetic field is negligible and has nothing to do with the process.


Yes? No? 


Jim

[jjasilli]

So per Ed’s comment, I don’t think the discussion is about whether or not we need a magnet.
Yes, we need a magnet. 

It’s about how the magnetic field is tickled for our signal.
No, because this pre-supposes the anti-Seth Lover idea -- that the string tickles the magnetic field. 

A pickup too high has the string deep in the strong lines of force. We lower the pickup and are moving out into the weaker lines.
Yes.  PU too high inhibits the free motion of the string. 

Is the output proportional to the string’s magnetism? Or is it just geography? 
Yes to both.  To generate a voltage we need to wiggle a magnet in the vicinity (geography) of a coil.  The PU magnet is always stationary with regard to the coil.  Hence the PU magnet cannot generate a voltage in the coil. 

So then, what is the function of the PU magnet?  It magnetizes the string.  The ferrous string becomes magnetized in the presence of the magnetic field of the PU's magnet (and ferrous pole pieces).  The string is now a magnet, wiggling near a coil; whereby a voltage is generated.  As you can see from the above posts, I've been dragged to this point of view, kicking & screaming all the way. 

If the magnetism of the string is the driving force (so to speak), strings would be ruined if brought too close to a pickup (pickup high). Yet we adjust the pickup down and it sounds just fine. What happened to the uber magnetism of the string?
Again, if the ferrous string is too close to the PU magnet, as extended by the pole pieces, then its amount of wiggle is constrained.  The less it wiggles, the less voltage gets generated.

This would also constrain the string's harmonic overtones, which in turn deadens tone.

If the string is too far, then it has both less magnetization, and less generative effect due to lack of proximity.  Harmonic overtones, being weaker than the fundamental tone, would again tend to drop out.

In between too close/ far is a range which will work, probably with a sweet spot.

[PRR]

Most string-wire has low remanence. It is attracted to a magnet but does not hold magnetism on its own.

IF the string WAS a good magnet, we could use magnetic strings and no-magnet pickups. Take the magnet out of the pickup, tie it on the string, you will get signal. However most magnets are too heavy for a rapidly vibrating system.

The indirect method with a fixed magnet and coil and a vibrating iron-thingie works well enough for guitar pups and for some other applications. (Some "MM" phono pickups are really fixed magnets and moving iron. "Sound-powered telephones" were fixed magnet and coil behind an iron diaphragm.)

[Ritchie200]

JJ - Yes, and no.  However, the cart does not pull the horse.


Faraday’s Law of Induction:  This law states that a wire conductor that creates movement through a magnetic field creates an electric current, and that the strength of the current is equal to the rate of change through the magnetic field. 


The wire can be ANY conductive material - Copper, brass, steel, unobtainium, etc.  The Law does not state a magnetic material must move through another magnetic field to create current.

We have all the pieces for an induction generator within the pickup.  We have a coil of wire and a magnet.  If we could spin that coil of wire between those magnetic fields (or vice versa)  I'm sure we could create several volts - considering the power of the magnets.  But that is not the function of the pickup.  As you said, we have a static setup.  The function of the coil is to detect the minute variations of the magnetic field when the string is vibrating in this field.  It just so happens that ferrous materials create the greatest disturbance in the field.  Think about this - a humbucker has magnets close together oriented N and S.  I would argue that the guitar string is in an area of null as far as magnetism.  If you put two magnets opposite and drag them along a piece of steel it will not magnetize the material because the fields cancel each other out.  So what is left to disturb the force of the magnet in our pickup?  The movement of the conductor (guitar string) and we are back to Faraday.  SO, if the output is based on a magnet in a magnetic field, then the humbucker should be less than a single coil and actually 0V.  Nope, that's simply not the case.   


"No because this pre-supposes the anti-Seth Lover idea -- that the string tickles the magnetic field."


Yes!  It does!  I'm sure Seth is a nice guy, but I'll stick with Faraday because he says so.  And he's a lot older.  Like me...

Get off my lawn!
Jim

[Ritchie200]

Yes come to think of it, magnetic phono cartridges are just that. Although Seth would say the record was magnetic....


Just kidding!  It was a joke!


Jim

[shooter]

"Sound-powered telephones"

they worked well but stink, oh laudy that rubber used in construction of them held the stink from  EVERYBODYS breath 

[jjasilli]

https://byjus.com/physics/faradays-law/
Faraday’s First Law:  Faraday’s first law of electromagnetic induction states that whenever a conductor is placed in the varying magnetic field, electromagnetic fields are induced known as induced emf. If the conductor circuit is closed, a current is also induced which are called induced current.

Ways of changing the magnetic field:
1.  By rotating the coil relative to the magnet.
Close enough.  Note that a guitar string once plucked settles into rotation

2.  By moving the coil into or out of the magnetic field. N/A


3.  By changing the area of a coil placed in the magnetic field.  N/A


4.  By moving a magnet towards or away from the coil. BINGO!

Faraday’s Second Law:  Faraday’s second law of electromagnetic induction states that the induced emf in a coil is equal to the rate of change of flux linkage. Here the flux is nothing but the product of the number of turns in the coil and flux connected with the coil.

Faraday's Laws state how it is possible for a PU to work. 

The Law does not state a magnetic material must move through another magnetic field to create current. No one is stating this, which may be the source of confusion.

However, I think it can be shown that the vibration of the string varies the magnetic field of the PU's magnet. If so, it appears that Faraday's Law would be satisfied.  Thought experiment:  we place a magnet on a table.  Suspended over that, we place iron filings on a horizontal piece of paper; the filings will take the shape of the magnetic filed.  Over that we move around an iron bar.  I think the filings will follow the iron bar around.  IOW, the presence & motion of the iron bar varies the magnetic field. 

Plug that into the PU situation and it seems that either explanation would satisfy Faraday's Law.

[shooter]

nice dive into Faraday beings back ancient memories 

one note;

 

place iron filings

don't get them in your PU's, If you've ever had to extricate them from a magnetic you will loath the day they were created 

[Ritchie200]

#1 would not apply as the coil is static. You are adding parts to Faraday's rule. AND, you are Presupposing Seth!  #2 and #4 are the same.  I don't believe they would apply because again the magnet is static to the coil.  Presupposing!   Adding parts and you are saying a magnet is required to move in a magnetic field to produce the signal.  That is not what Faraday is saying.

Let's get back to a humbucker.  Opposed magnets would impose zilch magnetism on the string.  If Seth's theory was correct, output would be 0. 

I like your thought experiment. I've always said the vibration of the string varies the magnetic field and was the basis for my beliefs and my tickle comment!

Jim

PS. I feel like I am talking to my daughter....  I wonder why?   For those not knowing, this is the ultimate compliment to JJ.

[jjasilli]

Thanks for the compliment!  And, we now concur -- i.e., we agree though perhaps for different rationales.

#1 would not apply as the coil is static.
Yes, though Einstein would remind us that motion is relative.  It shouldn't matter whether the coil or the magnet moves; and that could only be determined by reference to some 3rd object, say the earth. 

Let's get back to a humbucker.  Opposed magnets would impose zilch magnetism on the string.
Humbuckers do not have opposing magnets.  They have opposing coils.

If Seth's theory was correct
It now appears to me that both theories are correct as alternate explanations of the same phenomenon. I.e., they are not mutually exclusive.  Sort of like arguing if an electron is a particle or a wave.

[Ritchie200]

Jim

[jjasilli]

Ok, it's one magnet using both its N & S poles, ea into one set of pole pieces.  I agree that this would seem to confuse a string.  It certainly confuses me.


Nevertheless, see https://en.wikipedia.org/wiki/Humbucker:



How humbuckers work
In any magnetic pickup, a vibrating guitar string, magnetized by a fixed magnet within the pickup, induces an alternating voltage across its coil(s). However, wire coils also make excellent antennae and are therefore sensitive to electromagnetic interference caused by alternating magnetic fields from mains wiring (mains hum) and electrical appliances like transformers, motors, and computer screens, especially the older CRT monitors. Guitar pickups reproduce this noise, which can be quite audible, sounding like a constant hum or buzz. This is most noticeable when using distortion, fuzz, compressors, or other effects which reduce the signal-to-noise ratio and therefore amplify the unwanted interference relative to the signal from the strings.


The direction of voltage induced across a coil by the moving string depends on both the coil winding direction and the polarity of the fixed magnet. On the other hand, the direction of current induced by external fields is only dependent on the direction of winding. Therefore, a humbucker has two coils wound in such a way to cancel hum and maximize signal when they are connected. By convention, humbucker coils are both wound counterclockwise; however, typically the outside ends of the coils are connected together so that the coil starts are out of phase. The magnets in the two coils are arranged with opposite polarity so that the string motion induces voltages across both coils that become additive (exactly the opposite of phase cancellation) when the coils are wired in this manner. Electromagnetic interference induces identical, or almost identical voltage across both coils, because they are directly adjacent, and therefore pick up the same interference. When the signals from both coils are summed together, the two noise voltages cancel each other out, while the signal voltages add.[7] This dramatically improves the signal-to-noise ratio. The technique has something in common with what electrical engineers call "common-mode rejection", and is also found in the balanced lines used in audio equipment.


The arrangement of the humbucker coils to achieve reverse current flow with opposite magnetic polarity in each coil is known as Reverse Wound, Reverse Polarity, or RWRP for short. This nomenclature does not indicate that the coils are wound in opposition, but that the current flows in opposition.
***
I did not realize these things. 

[Ritchie200]

Bah!  Another Seth fan lemming....

Jim

[Ed_Chambley]

Jim,
In regards to humbuckers, the magnet is a bar magnet.  For instance, Gibson paints one end black.  This 1 magnet creates a wider field due to having 2 sets of metal pole pieces, but not opposing.  The coils opposed, but the pole pieces are not.  For instance, a Mexican stratocaster body has a 2 round cutouts differing it from an American.  You can use these to make coil areas for single coils and they will be somewhat humbucking.  This is not a new idea as John Suhr would like you to think.  For years session players in Nashville would rout a center hole under the pick guard and put in a pickup with the magnets removed.  It simply receives the magnetic field on that side of the pickup.  Alembic was doing this in the 70's.


A humbucker is not really 2 single coils together. as JJ refers to as well.


I do know you are talking from theory and if a tree falls in the woods and if no one is there to hear it, it still makes a sound.

[Ritchie200]

Ed, It's shiny brand new technology if I can put my name on it first! Yes, I do understand how the Humbucker works.  It's funny how things have progressed over the years before the flood of information available to anybody on the Internet.  I have old Guitar Player magazines from the 70's with marketplace ads of regular Joes wanting to correspond with anyone about pedal designs, amp mods, etc.  Even the amp mod "gods" of the 80's are not so special after all, but they were back then!

The Seth premise states the pickup magnet magnetizes the strings which only then the coil will detect.  If the pickup magnet is oriented so the pole pieces are N, the "magnetized" string would be S.  That is how it works, as there is now an attraction between the two.  My argument is that with a humbucker you have two sets of pole pieces, each being N and S facing the strings.  The magnetic fields are effectively cancelling each other out in regards to their ability to magnetize the strings (this has nothing to do with the coils). If the Seth premise is correct we have no magnetized string for the coil to detect and therefore the output would be 0 or significantly lower than a single coil with single orientation pole pieces.  IMHO this is where the Seth postulation falls apart.  This is also where his conclusion is in direct conflict with Faraday.

Jim

[sluckey]

Yawn... sigh... What time is is?

[Ritchie200]

Another test would be to hold a magnet above a single coil pickup pole piece so they are attracting.  Again this would place the string in a null space as far as being magnetized.  If we can still get a signal....  Drop mic.  I will attempt this tonight.

Jim

[Ritchie200]

Yawn... sigh... What time is is?

Why don't you go out and wander aimlessly in the woods or something? 

Jim

[PRR]

> hold a magnet above a single coil pickup pole piece so they are attracting.  Again this would place the string in a null space as far as being magnetized.

Well, try it.

My impression is that a true "null" may be almost impossible. You can null a point but not a space, and whatever is going on is more than a zero-size point. But a change of level would be suggestive.

[shooter]

My impression is that a true "null" may be almost impossible

totally agree

side-tracking;

in MRI, one of the 1st BIG calibrations after voltage n normal ya I'm here stuff is shimming, making a perfect (close) magnetic field within a 40cm sphere, average cal time 2 techs @12hours each IF everything is spot on, otherwise closer to 3 days of fighting dimples and bulges.

back;
you have dispelled an ASSUMED myth I've had about PU's -
I've assumed the little screws in each coil were "tuners" like tuning coils in TX/RX stuff.  ah well, now I'm stuck with knowledge 

[jjasilli]

Ditto to PRR.  I also suspect that it is impossible to isolate the variables to rule out one of these supposedly alternate theories.  You need a ferrous string, if only to wiggle the PU's magnetic field.  Once the ferrous string is present, it itself becomes magnetized.  So the string is both a magnet wiggling near a coil; and a ferrous rod varying the PU's magnetic field.  This is why I think either explanation works.


Even if one explanation were proven false, either one seems sensible enough so as not to be ridiculed. 


@ Ed:  Until this thread I never understood how a humbucking PU works.  Now I think I do, assuming the Wikipedia article is correct.  The humbucker has one primary magnet with 2 sets of pole pieces - 1 set of pole pieces arranged along each pole of the magnet.  Each set of pole pieces is surrounded by a coil wound in the Same direction (conventionally, counterclockwise).  Conventionally the 2 coils are connected Out of Phase with each other.


The coils do 2 things:
1.  They act as antennae picking up ambient noise and hum.  Because they are so close together the 2 coils pickup the same ambient nose & hum.  As antennae they are immune from the magnetic field.  Hence the noise & hum voltages generated in ea coil have the same polarity.  Because the coils are connected together out of phase, the noise & hum voltages cancel ea other out.

2.  As inductors picking up string vibration, the polarity of signal voltage in ea coil Is subject to the direction of each magnetic field.  Hence the signal voltages within each coil are in opposite phase; but the coils are connected together out of phase, thereby putting the 2 signal voltages in phase, once so connected.  So the 2 signal voltages sum (add together), while the noise voltages subtract.  Even if the noise rejection is imperfect, the signal to noise ratio is enormously increased.

[shooter]

humbucking

sounds a lot like this from the cobweb archives 

https://en.wikipedia.org/wiki/Differential_signaling

[Ritchie200]

I also agree with PRR, but if Seth is correct, I should be able to affect output CONSIDERABLY based on how close I can get.


Jim

[sluckey]

Why don't you go out and wander aimlessly in the woods or something? 

Jim

That was my feeble attempt at what you do so well.   

You do know that photobucket is gonna send you a bill for all those hits on that unavailable pic?

[PRR]

Copper conducts electricity.

Iron conducts magnetism.

Iron is *also* a good string material. Somewhat heavy but can be tuned to HIGH tension.

We have stationary magnet and coil, vibrating iron string.

Most of the flux path is through air (or wood) but some is pup frame and the key part is in the vibrating iron string.

In the simple case, the string vibrates closer/further from the magnet. The flux lines are short/long. Flux in coil is higher/lower. The steady flux makes no output(*). The varying flux makes a varying voltage.

[jjasilli]

Why don't you go out and wander aimlessly in the woods or something? 

Jim

That was my feeble attempt at what you do so well.   

You do know that photobucket is gonna send you a bill for all those hits on that unavailable pic?

Don't forget your muzzleloaders!

[Ritchie200]

Why don't you go out and wander aimlessly in the woods or something? 

Jim

That was my feeble attempt at what you do so well.   

You do know that photobucket is gonna send you a bill for all those hits on that unavailable pic?

I have NO idea what you are talking about, toaster boy.

You can see how much success photocrap has had collecting from me so far.

Jim