Use Multi-Section Windings to Reduce Self-Capacitance

[Leo_Gnardo]

I once read about a desease called the tourette syndrome, that can't be cured by decaf.
BTW, who cured our problem?

I thought Tourette's manifested through speech aberrations. Perhaps we witnessed a previously unreported version that affects typing. Alert the medical press! Psychology Today must be informed... Or more likely this was an encounter with a nut, ein toller mensch. That happens around here typically once or twice a year.

And God bless Warren Zevon, he's got a song for every situation. Solving our problems for us even though he's long gone. Good call rjb! Perhaps our new friend is now back to his regular activities, staying up all night listening to Mohammed's radio.

[J M Fahey]

What is this big deal about the Miller effect? It just means that the input impedance of the amplifier is higher than you might expect if you did not know about it.

Unless I understood you wrong, thanks to Miller effect amp stage input impedance (at least at high frequencies) is *lower*.

You now have a capacitor in parallel with input, so all it can do is lower the total value.

[Joe Gwinn]

No, the geometry is different. You can look at this as two coils, each with inductance L, where the inductance of the series combination is greater than 2L but less than 4L, because they couple, and we do not know the coupling coefficient. In the single coil case you have to consider the coupling of each turn with each other turn. Of course, you can look at the split bobbin case as one coil, and then you have to consider the coupling of each turn with every other turn also. I see no reason say the two cases are the same, or different, or by how much.

The inductance will be slightly less for sure, but not dramatically so. And one can always put a few more turns on each of the two sections.

[Joe Gwinn]

If what you were saying was true, the inductance would have a linear relationship with the turn count, which is to say a simple multiplication, but that's not the case, it's the square of the turn count, due to flux linkage.

Not so. The argument is that the locations of the single turns of the coils are not much changed by interposing the separator.

[Joe Gwinn]

The application specific implications of Miller capacitance are still not entirely clear, but that aside, I still think a low C guitar pickup is valuable for the same reason a low C guitar cable is valuable. It comes from the basic assumption that voltage is the objective, that L and C are unwanted side effects, and that to the extent they're not, you're afforded more flexibility if you add them back in, in a deliberate way.

All that Miller Capacitance does is to increase the input impedance of the guitar amplifier, and decrease its bandwidth. This may or may not be considered a problem. If this is a problem, there are multiple ways to reduce the effect, cascode input circuit topology being one.

The other way is to go from a 1 Mohm input impedance to say 10,000 Ohms, with everything scaled appropriately.

I've seen threads talking about lower capacitance due to thicker build magnet wire or "scatter winding", and the lowest C I've ever measured in a typical Strat pickup comes out to around 80pF at best. If a capacitance as low as 30pF can be achieved with a sectioned coil, it pretty much renders all other that other discussion moot.

Exactly. But all those methods will still work on the section coils, so going from one section to multiple sections is just a new degree of freedom.

[Helmholtz]

All that Miller Capacitance does is to increase the input impedance of the guitar amplifier

Sorry, no. The Miller effect increases input capacitance not input impedance, as JMF already indicated. I gave real measured values above. But amp input capacitance is rather irrelevant for the topic of our thread, it just adds to the cable's and PU's capacitances.

[Mike Sulzer]

Unless I understood you wrong, thanks to Miller effect amp stage input impedance (at least at high frequencies) is *lower*.

You now have a capacitor in parallel with input, so all it can do is lower the total value.

Should read input capacitance is higher. Sorry

[rjb]

On not dignifying that reply with a reply

Way

You may do dirty things to the hole at my back

I admit that "the Warren Zevon post" was mean-spirited. If we were in grammar school, it might even be considered cyber-bullying. But still, I find the corn-holing metaphor a bit melodramatic. The only excuse for my behavior is to note that drastic times call for drastic analogies, and sometimes we must fight assholes with assholes.

- but please do not make fun out of other users.

I don't quite understand this. Idiomatic phrase?

I point this out a second time to users, which contributed -well- almost nothing to the thread.

Compared to what?

Look into the mirror, if you want to laugh about humans.

No problem there. I laugh at myself several times a day. You should try it.

P.S.: Nietzsche was just an overwhelming huge asshole. That is my opinion. Flush his so.called philosophy down the toilet...

I agree. But even overwhelming huge assholes are occasionally right. That "Without Music Life Would Be a Mistake" signature is merely one in a series of quotes about music and/or perception.

Sorry folks. I just had to get that off my simile.
-rb

[Leo_Gnardo]

hopefully the end of here,

I admit that the Warren Zevon post was mean-spirited.

It was spot on. No apologies necessary.

If we were in grammar school, it might even be considered cyber-bullying.

We're adults here, mostly. I don't have much patience for coddling those who show up out of nowhere to exert their aggressive behavior on the website. If Herr Dudelsack is offended, he can call his daddy to send lawyers, guns & money to straighten the whole thing out.

I think ya done great rjb. Now let's carry on with the mystery of multi section windings.

[bbsailor]

Not so. The argument is that the locations of the single turns of the coils are not much changed by interposing the separator.

Joe,

I believe that the real issue is, what is the relative voltage induced in various parts of various shape coils. The diminishing induced voltage occurs with turns farther below the strings and farther horizontally away from the pole piece magnetized portion of the string. The factors that add inductance or capacitance just reshape the most efficient portion of the coil where the most voltage is induced in the coil wire turns.

Joseph J. Rogowski

[ken]

And God bless Warren Zevon, he's got a song for every situation. Solving our problems for us even though he's long gone. Good call rjb! Perhaps our new friend is now back to his regular activities, staying up all night listening to Mohammed's radio.

He'll be back... with lawyers, guns and money

I just compared the output levels of both halves of a stacked humbucker, which is geometrically similar Fender Vintage Noiseless, Analysis and Review | GuitarNutz 2 , the bottom coil produced about 9dBV less than the top coil. If the partition was thinner, the loss would not be as great, but I'm sure it would still be significant.

Note that with a stacked humbucker, the lower coil is out of phase with the upper coil, so the series output of both coils is lower than the top coil by itself. The loss in that case is about 3dBV.

This I don't understand. Why is this true, and is this true with all humbuckers not just the vertically stacked ones?

Ken

[Antigua]

This I don't understand. Why is this true, and is this true with all humbuckers not just the vertically stacked ones?

Ken

All humbuckers are wired out of phase, but a normal PAF type humbuckers have the magnetic fields of it's slugs and screws in opposite polarities, so that the string generates two voltages that are also out of phase. Since the phase of the string movement is effectively flipped twice, the string movement back in phase again, but the noise is only flipped once, so it's remains out of phase, and is cancelled.

With a stacked humbucker, there is no double flipping, because both coils are along the same magnetic axis. With a stacked humbucker, the moving guitar string and external noise are both cancelled out (to some extent) at the same time. The only reason you hear more guitar string than you do noise is because the top coil is much closer to the string than the bottom coil, while both coils are about the same distance from the noise sources. That's why if you disconnect the bottom coil the overall output is higher, because it's no longer cancelling out the guitar string along with the noise. It's like you have a dummy coil, and you're placing the dummy coil in one of the worst possible places you could locate one in the guitar, all for the sake of keeping the two coils together as one modular unit, which is easy to package, sell and install.

A PAF type humbucker is really ingenious because it not only cancels noise, but it also ends up producing more voltage, because it also places more turns of wire closer to the strings. Maybe the only "down side" of a PAF is the physical comb filtering that you get from having the two coils somewhat far apart. But then, if you have a thin "rails" type humbucker, like Bardens, comb filtering is no longer an issue either, and so for that reason, I'd say Strat/Tele "rail" type pickups are the least compromising noiseless, passive pickups available.

[Joe Gwinn]

I believe that the real issue is, what is the relative voltage induced in various parts of various shape coils. The diminishing induced voltage occurs with turns farther below the strings and farther horizontally away from the pole piece magnetized portion of the string. The factors that add inductance or capacitance just reshape the most efficient portion of the coil where the most voltage is induced in the coil wire turns.

All true, but my argument is geometric - the turns have not moved all that much. It is true that the order they are strung together has changed, but that makes no difference.

Said another way, the proposed separator has no effect on how far the turns are from the cores. Only the lateral spacing is slightly increased.

In production, I would wind both sections at the same time, from two spools of wire, so the side pressure on the seperator is balanced. And to cut winding time in half.

[Antigua]

Said another way, the proposed separator has no effect on how far the turns are from the cores.

It sounds like you're saying that it's because of the core that in increase in inductance per turn is not linear, but it's not linear even if the core happens to be air.

[Mike Sulzer]

All true, but my argument is geometric - the turns have not moved all that much. It is true that the order they are strung together has changed, but that makes no difference.

When you say it is geometric, I am not sure what you mean, but I think you are thinking of something like the formulas that apply to single layer coils, length, height, etc. It cannot be that simple for multi-layer coils in general because there are so many possible ways to arrange the windings even while keeping the "geometry" of the coil the same. Yes, you can derive formulas for multi-layer coils under some circumstances. For example, there is one contained in this: https://nvlpubs.nist.gov/nistpubs/Sc...18p737_A2b.pdf. But I do not think that applies to the situation here.

The issue is the amount of flux generated by current in each turn passes through each other turn. You have not said anything about why that would not change significantly with two very different ways of winding wire on a coil with the shape of a pickup.

Edit: I see what you are saying. Sorry to be so slow. First consider this (theoretical, not practical): wind the turns on the coil individually, leaving each one unconnected, that is, just with the two ends of each loop sitting close to each other. Now consider different was of connecting them in series, presumably using twisted pairs that have zero resistance and occupy no space. Then no matter what order we connect them in all the flux generated by each turn passes through each other turn in an identical way. I am not quite sure this represents the actual case closely enough, but it probably does.