multi-gauge wire humbucker question

[David King]

So no one is willing to come out with a workable mathematical formula for hitting the hum-canceling nail on the head with two different gauge wires?

[David Schwab]

So no one is willing to come out with a workable mathematical formula for hitting the hum-canceling nail on the head with two different gauge wires?

I thought it was already stated; you wind the same number of turns for each gauge. That's all you have to do.

[David Schwab]

Well... in this case they're sidewinders. I've been winding these for 20 years (perhaps almost as long as you!) and I actually connect them in electrically in-phase series (head to tail) but point them in opposite directions. Not that there's not a big chance of me screwing up, but if I had done so I'd notice a quite unexpected timbral quality before the hum thing became apparent.

Oh I didn't realize you were talking about sidewinders. I notice if the sidewinders are wired up wrong they hum but don't sound all that much different. I also find i have to make sure the poles are grounded and I shield the entire pickup, otherwise they seem susceptible to buzzing.

I set my coils up with both tops facing the poles. Because of that the windings are in opposite directions, then I wire them in phase. The same magnetic polarity is facing the poles.

And in fact, my neck pickup (also a sidewinder) is also a multi-guage unit and is nearly dead quiet.

By the way, this "sidewinder" term is something I learned from you, and is much more convenient than my previous "horizontally opposed coaxial" monicker.

I didn't make it up!

[fieldwrangler]

I notice if the sidewinders are wired up wrong they hum but don't sound all that much different.

Yes; and this sort of thing sometimes scares me. Makes me feel that there's something fundamentally funny about this design, sorta like early stacked Strat pickups with limited magnetic isolation between the coils. I do however, continue to bark up this tree with a vengeance.

I also find i have to make sure the poles are grounded and I shield the entire pickup, otherwise they seem susceptible to buzzing

I'm pretty obsessive about those grounding/shielding issues.

[David King]

I thought it was already stated; you wind the same number of turns for each gauge. That's all you have to do.

David,
Where did you get that from? That would be great news if it's true, I just want to make sure we can put this to bed before we get totally sidewound on other topics...

[fieldwrangler]

I just want to make sure we can put this to bed before we get totally sidewound on other topics...

Excellent point. I believe I might justifiably be accused of being a Serial Hijacker; I'm never quite sure when to just start a new thread.

Bob Palmieri

[David Schwab]

David,
Where did you get that from? That would be great news if it's true, I just want to make sure we can put this to bed before we get totally sidewound on other topics...

Well, we can start with the DiMarzio patent 4501185:

The present invention avoids the shortcomings of prior two-coil hum-bucking pickups by winding the coils such that both coils of the pair have substantially the same number of turns but are wound with wire of different diameter or gauge. It has been found that by means of this construction, low frequency cancellation is emphasized, providing more effective elimination of 60 cycle hum without affecting the higher harmonics of the 60 cycle signal which may contribute to the desired tonal qualities. Moreover, because of the difference in impedance characteristics resulting from different diameter wire on the respective coils, overall frequency response can be selectively adjusted to provide improved tonal qualities.

The transducer construction, as thus far described, is conventional, and is generally as disclosed in the Lover patent cited above. However, there is an important difference, namely, the diameters of the wires constituting the coils 28 and 30 are different. In particular, the wire size in one coil is appreciably different from that of the other coil. Both coils 28 and 30, however, are wound substantially with the same number of turns. As an example, one of the coils 28 and 30 may be wound with 5,400 turns of 42 gauge wire, while the other coil may be wound with the same number of turns of 44 gauge wire (American gauge standard).

And I know it works because I have been making a model of pickup this way for the last three years. I started doing it when I made two different prototypes I liked, and tried combining a bobbin from each one. You can alter the ratio between the coils, and also change which coil is near the neck and bridge, to get different tones.

[frankfalbo]

Rather than attempting to define a recipe for noise cancellation in a hybrid, let's pretend your two coils are dead equal, same wire gauge. Wrapping one in copper shielding tape, and leaving the other unwrapped will make one coil noisier than the other, right? Try isolating your keeper bar and screws from ground, while ensuring all 6 slugs are well grounded. That screw coil may be noisier, right? So when looking for the perfect hybrid gauge recipe for cancelling hum, the wind is only one of many factors that can fine tune your noise levels between the coils. That's why I like to think of the noise as audio and the hum cancellation as an audio exercise, rather than come up with mathematical formulas. Dimarzio doesn't target 100% noise cancellation with their hybrids. They probably target a tone, and that's why some of their humbuckers are noisier than others. I'd rather approach hybrids that way than to focus on noise when crafting the recipe. Then, after you know the tone recipe you're aiming for, you can work to massage noise into and out of the coils individually to get it even closer. I mean, does one turn of 44AWG really pick up the exact same amount of noise as one turn of 42?

[David King]

Frank,
I agree with you in principle but I'd tend to go at it on the opposite direction. Start with quiet coils and then work towards the sound I want. It's all going to depend of which cart and which horse you want in the picture.

[Mike Sulzer]

Rather than attempting to define a recipe for noise cancellation in a hybrid, let's pretend your two coils are dead equal, same wire gauge. Wrapping one in copper shielding tape, and leaving the other unwrapped will make one coil noisier than the other, right? Try isolating your keeper bar and screws from ground, while ensuring all 6 slugs are well grounded. That screw coil may be noisier, right? So when looking for the perfect hybrid gauge recipe for cancelling hum, the wind is only one of many factors that can fine tune your noise levels between the coils.

That strategy for balancing noise cancellation is flawed. There are two entirely independent kinds of noise sources:

1. magnetic fields

2. electric fields

Magnetic fields are canceled by using two coils with the same sensitivity wired so as to receive the noise magnetic fields with opposite polarity.

Electric fields can be shielded with a grounded conducting surface or canceled with a differential amplfier when the same electric field appears across both coils.

Different locations have different relative intensities of interfering magnetic and electric fields, and the fields in different locations point in different directions. You cannot make a scheme in which you attempt to achieve an overall cancellation of hum by involving both kinds of fields together. If you wish to achieve cancellation in all environments, you must make one method for canceling magnetic fields, and another independent one for the electric fields.

However, it is the magnetic cancellation that is most important. For example, this is why humbuckers can do well without the cover, which is effective for shielding electric fields, but the partial shield of the base plate is often good enough.

[Joe Gwinn]

Joe - Do you have any good resources to learn more about area-turns product? Are you aware of any matematical way to calculate this measurement? I would be great to be able to have a formula to calculate "approximate" required measurements for hum cancellation when dealing with multigauge.

Sorry for the long pause. I've been too busy at work,.

Area-turns product is just that. Think of a single closed turn made of thin wire. This turn need not be a circle, and may be bent as well. Mount the turn on a holder of some kind, dip the ring in bubble-blowing solution, and smoothly withdraw the turn from the solution. Do not blow any bubbles. There will be a thin soap-film membrane in the turn now. What is the area of this membrane?

So, this is one turn. If one had 50 such turns assembled into a 50-turn coil, the coil's area-turns product would be fifty times the area of that membrane.

This is for an air coil. If there is any ferromagnetic material nearby, the effect of the area is multiplied by the effective permeability of that ferromagnetic material.

The area-turns product is important because the voltage induced in a turn by a changing magnetic field is proportional to the amount of flux linking that turn, which is in turn dependent on the area of that turn and its angle to the magnetic field. This is Faraday's Law of Magnetic Induction. Here is the Wikipedia article: Faraday's law of induction - Wikipedia I have been looking for a good diagram, and so far this is as good as any. In the archives there is a thread where I explained the area-turns product, and decoded the fancy-looking mathematical formula used to express Faraday's law of induction.

[David King]

Joe,
Is there some mathematical shortcut to derive the extra turns needed of a smaller gauge wire onto two identical bobbins once we know the proportion of the cross-sectional areas of the two wires in question? I bet the ratios of the different wire's cross-sectional areas and the extra turns needed to equalize the turns area products will have a fixed coefficient.

I suppose scatter winding may throw off the calculations a bit.

I'm keeping this strictly air-core coils for now.

[David Schwab]

David, just wind up two coils with the same number of turns and see what you get. I don't get any hum at all with my pickups. If you really want the coils to be about the same size you can use heavy build insulation on the thinner wire.

[fieldwrangler]

Frank,
I agree with you in principle but I'd tend to go at it on the opposite direction. Start with quiet coils and then work towards the sound I want. It's all going to depend of which cart and which horse you want in the picture.

I, too, go for quiet first then tune for tone.

Bob Palmieri

[fieldwrangler]

That strategy for balancing noise cancellation is flawed. There are two entirely independent kinds of noise sources:

1. magnetic fields

2. electric fields

Magnetic fields are canceled by using two coils with the same sensitivity wired so as to receive the noise magnetic fields with opposite polarity.

Electric fields can be shielded with a grounded conducting surface or canceled with a differential amplfier when the same electric field appears across both coils.

Different locations have different relative intensities of interfering magnetic and electric fields, and the fields in different locations point in different directions. You cannot make a scheme in which you attempt to achieve an overall cancellation of hum by involving both kinds of fields together. If you wish to achieve cancellation in all environments, you must make one method for canceling magnetic fields, and another independent one for the electric fields.

However, it is the magnetic cancellation that is most important. For example, this is why humbuckers can do well without the cover, which is effective for shielding electric fields, but the partial shield of the base plate is often good enough.

Well... I guess I like a less partial shield in general.

So, what do you think are the primary sources of problematic magnetic fields (besides transformers?)

Bob Palmieri