Theoretical Dilemma about Humbucking PUs

[xxxchange]

Hi, I was wondering whether it might be possible to stack two single coils to create a humbucker, but not the usual way, with one "dummy" single coil just for the sake of hum canceling, and only one operational.

The ideas is thus: to have one single coil mounted under the strings, and another right above the strings...

How would you need to wind the wire and what would be the magnets orientation so that the signal from both PUs adds (if possible)?

For instance, in the classic Rick's horseshoe PU there's only one coil under the strings, but strings are magnetized with different poles above and under them. Could you add a second bobbin above, to create a sort of humbucker? (forget practical considerations, as to the space needed to fit the coil)

Regards,

XC

[Mike Sulzer]

Dummy coils work (old idea). Coils with the same sensitivity to magnetic fields connected electrically out of phase cancel hum if they are close enough to see the same field.

They do add inductance to the circuit, though, if connected in series.

[Stealth]

Same as you'd do with a normal humbucker. The lower (internal) one would be wound in one direction and polarized in one direction, say, clockwise-wound and north facing the strings. The upper (hovering) pickup would be counter-clockwise-wound and south facing the strings. I don't believe anything else would be required.

As to whether the top coil would be magnetized or non-magnetized (dummy), that's anyone's choice. A dummy coil in that position doesn't sound like a good idea as it'd likely cancel a few frequency components too many.

[David Schwab]

Hi, I was wondering whether it might be possible to stack two single coils to create a humbucker, but not the usual way, with one "dummy" single coil just for the sake of hum canceling, and only one operational.

LOTS of hum canceling single coil size pickups are made this way.

Below you see a Kinman, a Dimarzio Virtual Vintage and an EMG-SA.

Even the old Les Paul Recording pickups were stacked humbuckers.

It works well but they tend to be thin sounding, so you have to wind them a lot hotter to compensate.

[xxxchange]

Thank you for the prompt replies, but you missed the point actually.

Sorry if I didn't make it clear enough.

People are so familiar with the idea of having PUs only beneath the strings that it's difficult to picture that you can place them anywhere.

What I mean is this: take a normal Humbucker: two single coils pickups, both beneath the strings, winded and with such polarities, that if wired in series (traditionally) the signal adds, and the hum gets cancelled...

Now the question is: can you get the same results, that is, two single coils that add their strength and cancel hum, but placing one beneath the strings and the other above?

I don't care if there's some awkward device to place the pickup over the strings, is it theoretically possible? If so how would you need to wind the two single coils and with which polarities?

None is dummy, both are operational, both should sense the strings, just one doing it from below, the other from the top.

Thanks,

X

[xxxchange]

To make it even clearer

The thing about the stacked humbucker has nothing to do with what I have in mind, since in that design both coils are on the same side of the strings, and only one of them senses the strings... the other is just for the sake of radio signal cancelling and does not contribute in any remarkable way to the sound...

What I mean is what would happen if you have a sandwich of single coil strings single coil. Is there any way to wind the PUs and put such polarities that the signal adds?

Again, both are perfect operational single coils, with their own magnets, etc. They are placed one on top of the other with the strings in between, and the variables we have are the wiring (I guess series), the polarities of each PU and the winding of each PU...

[Ronsonic]

The thing about the stacked humbucker has nothing to do with what I have in mind, since in that design both coils are on the same side of the strings, and only one of them senses the strings... the other is just for the sake of radio signal cancelling and does not contribute in any remarkable way to the sound...

It is the same thing as any other humbucker, stacked or side by side, except the coils are a little further apart making them less effective at rejecting noise. Feel free to locate the coils where you like.

[xxxchange]

Well, there's something different yet...

It is the same thing as any other humbucker, stacked or side by side, except the coils are a little further apart making them less effective at rejecting noise. Feel free to locate the coils where you like.

Since when the coils are located side by side there might be some slight canceling, due to the modes in which the string vibrates in opposing phase in each region. That's not a big problem for humbuckers since for the most part, what the pickup "sees" is the same string motion....

That is, for really high modes (almost inaudible in the top strings, somehow audible in the bottom ones), the humbucker is unable to effectively sense them...

Now, the DILEMMA, is what would happen in the case of having two single coils sensing the same REGION of the strings, just one from above and the other from below?

This is a different case in which the pickups "see" the same, but from different perspectives, so that one string getting closer to one would mean getting further away from the other (this problem hardly occurs in traditional humbuckers)...

How would you need to coil them, and how the polarities would be, so that the movement of the string getting closer to one ADDS to the movement of the string getting further apart from the other... Since that would be the case mostly...

... so what we are trying to avoid is that the pickups interfere with each other in a destructive way, we would want them to add their signals,....

I know it's impractical for guitar like instruments, but I was thinking of another instrument of the harp family that due to limitations of space for pickup placement, would greatly benefit of having one coil on each side of the strings, if that would create some sort of humbucker. Even if it's not as effective at canceling hum as bobbins placed side by side, if you get the sturdier sound, you would still be better off than with only one single coil...

Thanks for the input,

X

[xxxchange]

You seemed to have gotten it right...

Same as you'd do with a normal humbucker. The lower (internal) one would be wound in one direction and polarized in one direction, say, clockwise-wound and north facing the strings. The upper (hovering) pickup would be counter-clockwise-wound and south facing the strings. I don't believe anything else would be required.

As to whether the top coil would be magnetized or non-magnetized (dummy), that's anyone's choice. A dummy coil in that position doesn't sound like a good idea as it'd likely cancel a few frequency components too many.

Yep, actually I think that you did understand what I mean. Sorry if I didn't reply to your comment earlier. What I don't understand is the thing about having the "hovering" pickup being dummy, I would get it out of the way and place it as in the (in)famous stacked humbucker if I didn't intend to generate signal with that other pickup...

With the windings and polarities that you suggest, would that mean that the signal generated from both pickups would add?

I am looking for as much constructive interference as possible, and minimizing destructive interference...

So I guess that if your windings/polarities produce a signal of the same sign when one string gets closer to the, say, "under the strings" pickup and when it gets further away from the "over the strings" pickup, that's it. We have a "stacked" humbucker with both single coils operational, and taking the width of one single coil.

Not a practical thing for any guitar-like instrument, I grant...

I know it's unbelievable cumbersome for a guitar to have a whole pickup assembly thing protruding over the top of the strings, but it's for some other instrument that I had it in mind, in which the player won't notice the difference...

[xxxchange]

A key word on this matter: PHASE

LOTS of hum canceling single coil size pickups are made this way.

Below you see a Kinman, a Dimarzio Virtual Vintage and an EMG-SA.

Even the old Les Paul Recording pickups were stacked humbuckers.

It works well but they tend to be thin sounding, so you have to wind them a lot hotter to compensate.

Hi, someone in another forum suggested one thing that I consider it to be some sort of keyword: the idea of PHASE.

Let's consider a regular humbucker: coils placed side by side, generate a signal that is already in phase, and very similar.

If you wire them out of phase, you only hear the slight difference between those signals, which results in a very thin sound. If you wire them IN PHASE, you get a stronger signal than each pick up separately.

...

Now, let's move to our case: by having the coils sensing the strings from opposite sides, you get already an out of phase signal (180 degrees). Am I right?

So if you wired them IN PHASE, you should get a very thin sound resulting, analogous to the normal humbucker wired out of phase...

But, if you wired them out of phase, the two signals would reinforce each other, producing a stronger signal than each pick up on its own.

....

Any comments are muuuuuch welcomed.

Cheers,

X

[uvacom]

It should work fine, it's just a matter of how practical it would be to build and whether it would interfere with picking technique to have all that stuff on top of the strings.

On the plus side, the vertical component of the magnetic field would be more uniform so theoretically the result would be a more accurate representation of the string's vibration - however, that could change any magnetic distortion introduced (such as the magnetic field being less strong towards the middle of the string's vibrational pattern) to third order and thus not as pleasant sounding.

[David Schwab]

Let's consider a regular humbucker: coils placed side by side, generate a signal that is already in phase, and very similar.

If you wire them out of phase, you only hear the slight difference between those signals, which results in a very thin sound. If you wire them IN PHASE, you get a stronger signal than each pick up separately.

No, a regular humbucker has both coils wired out-of-phase to each other. It's usually the two finish leads from the coils that are connected together. Phase is actually the wrong term, as it implies a time domain effect, but it's commonly used. having the two coils electrically out of phase cancels common mode noise.

The reason why you don't have cancelation of the string's signal is because each coil also has opposite magnetic polarity, which puts them back in phase. If they were wired in phase with the opposite magnets they would sound out of phase. If the magnetic polarity were the same in both coils and they were wired in phase, there would be no bucking of the hum.

If they are facing each other, it depends on which direction the wind is going. If the two coils are wound in the same direction and are facing each other, then you wire them in phase.

[xxxchange]

Thanks a bunch for clarifying all that options for me...

No, a regular humbucker has both coils wired out-of-phase to each other. It's usually the two finish leads from the coils that are connected together. Phase is actually the wrong term, as it implies a time domain effect, but it's commonly used. having the two coils electrically out of phase cancels common mode noise.

The reason why you don't have cancelation of the string's signal is because each coil also has opposite magnetic polarity, which puts them back in phase. If they were wired in phase with the opposite magnets they would sound out of phase. If the magnetic polarity were the same in both coils and they were wired in phase, there would be no bucking of the hum.

If they are facing each other, it depends on which direction the wind is going. If the two coils are wound in the same direction and are facing each other, then you wire them in phase.

Thanks to your last comment I am beginning to understand something in electromagnetism applied to pickups... actually it would be great if there's some detailed explanation on this.

I mean, everywhere you can read: the string disturbs a magnetic field, and the disturbance induces an electrical current on the coil of wire. Yeah, right, but how exactly it's done, I have never stumbled upon a really detailed explanation of the process.

I always suspected that PHASE was somehow abused as a term, as you point out.

So, if I get you right, in the normal humbucker you connect the two coils "out of phase" (notice the brackets), that is,

one BEGIN is lead,
the two ENDS together
the other BEGIN goes to ground

AND, the polarity of the magnets is NORTH up in one coil, SOUTH up in the other.

AND, the winding is both CW or CCW.

So far so good....

Now, for our particular case, of having the coils on each side of the strings...

The desired arrangement would be, please feel free to correct as needed,

"out of phase" (as before, otherwise you don't get radio interference cancellation, so that means both ENDS together, one BEGIN lead, the other ground).

AND THE MILLION BUCK QUESTION, the polarity of the magnets...

since we want our signal to add up, and the wiring is already "out of phase" to cancel hum,...

the big difference here is that the coils get a different, maybe "out of phase" picture of the string motion (conversely to the traditional pickup, in which both pickups "see" more or less the same)...

so it follows that they are already producing an output "out of phase" with each other, which is already compensated for the "out of phase" wiring, so if we have two opposing polarities, that would put them "out of phase" a third time, having a thin sound...

so the correct polarity would be like in a regular humbucker, NORTH up in one, SOUTH up in the other, that in our particular case would mean that both pickups have the SAME POLARITY FACING THE STRING....

the winding can be as usual both CW or CCW.

Am I right?

Thanks again, cheers,

X

[xxxchange]

To summ all up...

If we take a regular humbucker, keep everything the same, wiring and polarity, and place one of the coils on top of the other, on the other side of the strings,

we would still get hum cancellation, as both coils are oriented the same way in regards to electromagnetic radio signals going through them...

and the signal generated would sum up, since even when the polarity that faces the string is the same in both cases (either both south, or both north), since the string motion is "seen" from the opposite side, the out of phase wiring between the two single coils would put them again "in phase".

How effective it would be depends on how well to the "out of phase" scheme corresponds the two pickups sensing the strings from different sides. If this really creates a close to 180 out of phase signal between the PUs, it should work... (in the case that the signal ressembles more a "in phase", then you should again put two opposing polarities facing the strings).

So a humbucker would still be a humbucker if you put one of the bobbins to sense the strings from above... interesting, don't you think?

[David Schwab]

So, if I get you right, in the normal humbucker you connect the two coils "out of phase" (notice the brackets), that is,

one BEGIN is lead,
the two ENDS together
the other BEGIN goes to ground

AND, the polarity of the magnets is NORTH up in one coil, SOUTH up in the other.

AND, the winding is both CW or CCW.

So far so good....

Generally humbuckers have both coils wound in the same direction. If you wind CW and CCW then you would wire them in phase.... start-end->start-end.

AND THE MILLION BUCK QUESTION, the polarity of the magnets...

since we want our signal to add up, and the wiring is already "out of phase" to cancel hum,...

the big difference here is that the coils get a different, maybe "out of phase" picture of the string motion (conversely to the traditional pickup, in which both pickups "see" more or less the same)...

so it follows that they are already producing an output "out of phase" with each other, which is already compensated for the "out of phase" wiring, so if we have two opposing polarities, that would put them "out of phase" a third time, having a thin sound...

so the correct polarity would be like in a regular humbucker, NORTH up in one, SOUTH up in the other, that in our particular case would mean that both pickups have the SAME POLARITY FACING THE STRING....

Look at it this way, you wire the two coils to have opposite polarity to cancel hum. But now they are out-of-phase with regards to the strings.

Then you give them opposite magnetic polarities to make them in phase with regards to the strings.

Both the magnets and the wiring puts them out of phase. Since they are out of phase twice, they are back in again.