need schematic for hum cancelling jazz bass pickups

[Marko Ursin]

David & Mike; I have an 10-coil pickup on my bass. Each coil is 1,75kOhm, 10 000 turns of 42AWG on each coil. It sure has thick low end and still sounds clear. How does wiring those coils 5 in series, then 2 rows parallel compare to 2 coils in series and 5 pairs in parallel? I find 5s 2p has more output and slightly more bass, when 2s 5p has a bit less output and a bit clearer sound. Why is that? I don't understand even half of what you are talking but I sure can hear what the pickup sounds like.
Marko

[Mike Sulzer]

David & Mike; I have an 10-coil pickup on my bass. Each coil is 1,75kOhm, 10 000 turns of 42AWG on each coil. It sure has thick low end and still sounds clear. How does wiring those coils 5 in series, then 2 rows parallel compare to 2 coils in series and 5 pairs in parallel? I find 5s 2p has more output and slightly more bass, when 2s 5p has a bit less output and a bit clearer sound. Why is that? I don't understand even half of what you are talking but I sure can hear what the pickup sounds like.
Marko

Yes, those two configurations should be significantly different. First, let's look at the inductance; Assume each coil has an inductance of x Henries. Make two sets with 5 in series. Each set has an inductance of 5x since inductances in series add. Now put the two sets in parallel; this makes the total inductance 5x/2. For 2s 5p case, each set of five has an inductance of x/5, and two in series have 2x/5. The ratio of the 2s 5p to 5p 2s is 4/25. When you combine this with the cable capacitance, the resonant frequency is increased by sqrt(25/4) = 5/2. This is more than a factor of 2 and should make quite a difference, the exact audible difference depending on how these frequencies relate to the useful range of the instrument.

For the output, assume that each each coil puts out y volts, and the impedance of a single coil is Z. Five coils in series have an impedance of 5Z. You can think of the 5s 2p case as a voltage divider where the top and bottom legs each have an impedance of 5Z. y volts coming from one coil is feeding the top leg, and the bottom leg then attenuates this to y/2. For the 2s 5p case, the five in parallel act like a voltage divider where the top leg has an impedance of Z, and the bottom leg has Z/4. This gives a voltage of y/5. So the 5p 2s has a voltage 2/5 as great. This is about 4 db down.

I am ignoring any loading effect of the following electronics, which could alter these results somewhat, but you can see approximately what is happening.

If you did 10s, you would get more output, but the inductance would be 10x, and the resonant frequency would be low, giving a less clear sound.

[Mike Sulzer]

Although I have not tried this, it seems likely string sampling effects are important in a bass as well as a guitar. (Sampling the string: differences between single coil and) This should be more of a problem when playing with a bright tone and not using flat wound strings. With a four string bass, it is easy to get hum canceling without using a humbucker like pickup where each string is sampled in two places, but it is harder with five strings.

The results of the discussion referenced above suggest a solution. One of the results of the discussion was that the filtering applied to a string by the two point sampling is a big effect on the no. 6 E string, but a small effect on the highest frequency strings. I would expect the effect to extend more across the strings on a bass, but still, the effect should be least on the highest frequency string.

The suggested solution is to use an individual coil on the four lowest frequency strings, alternating the magnetic and electric polarities in the usual way to get hum canceling. Then the fifth string would use a pair of coils, each about half the number of turns of the others, arranged along the string in the usual way and polarized for humbucking. All coils would go in series, wound with the number of turns necessary to give the required total inductance,

[David Schwab]

Mike, the pickup in question, which is also the same pickup Marko is speaking of, has two coils per string. So it is a conventional humbucker.



Each row measures 10k. In parallel with the next row would of course be 5k. But it still sounds very different from a pickup with two coils wound the same, and wired the same.

It even sounds very clear if you wire the two rows in series. I've tried this. What I said earlier, which you didn't think was relevant, was that in series at 20K it was very clear, which a thick sounding low end, and bright top end. In comparison a two coil sidewinder wound to 20K, e.g., the Gibson mudbucker, has very little high end and a very pronounced midrange. I'd speculate that the mudbucker has more wire on it, but I don't know that for sure. The Wal pickup has 10,000 turns on each of it's small coils, so it's still not small amount of wire. Both pickups are wound with 42AWG.

[David Schwab]

I'd also argue with anyone who wants to argue that the single string coils have less DCR resistance (less wire length) overall per number of strings for a given number or turns than a traditional coil. Not sure what effect this will have, most likely just less overall capacitance, hence brighter.

They clearly have a higher resistance than a single similar size coil, and more turns as well. But they don't sound like a single coil wound to the same resistance.

[David King]

OK I fold. BTW the coils inside the Bart J pickups are tiny, about a quarter the size of the ones in the MKIVs

[Mike Sulzer]

Mike, the pickup in question, which is also the same pickup Marko is speaking of, has two coils per string. So it is a conventional humbucker.

Then I am confused as to why you are comparing it to a mudbucker, which is a whole different kind of thing. I am also puzzled by the parallel-series comparison. Maybe I am wrong in thinking you have it connected to a guitar cable, but maybe right into a preamp with not much capacitance across it?

[David Schwab]

Then I am confused as to why you are comparing it to a mudbucker, which is a whole different kind of thing.

Because generally if you wind a pickup to 20K with 42 gauge wire it will sound very dark, like a mudbucker. That's why they wound that much wire on that pickup. They wanted it to sound like the pedals on a pipe organ.

The Wal pickup has essentially the same amount of wire, as seen by the DC resistance, but sounds bright and clear in comparison. The Wal pickup also has a lot more steel to it (two large keepers), and they both use ceramic magnets.

The Wal pickup also sounds very different from a pickup wound with less wire in that the low end has a distinctive thickness about it.

[Mike Sulzer]

Steel: Where it is matters. A heavy keeper outside the coil has a lot less effect than steel in the core, as far as inductance is concderned So I think the mudbucker with its large core really has effectively much more steel. Also the area of the steel core is much greater in the mudder, and the higher voltage around that path drives eddy currents more effectively. So you move the resonance down in frequency with a high inductance, and then damp it with eddy currents, and you are left with mostly bass. This is why I think you cannot really compare the Wal and the mud pie by looking at just resistances.

Because generally if you wind a pickup to 20K with 42 gauge wire it will sound very dark, like a mudbucker. That's why they wound that much wire on that pickup. They wanted it to sound like the pedals on a pipe organ.

The Wal pickup has essentially the same amount of wire, as seen by the DC resistance, but sounds bright and clear in comparison. The Wal pickup also has a lot more steel to it (two large keepers), and they both use ceramic magnets.

The Wal pickup also sounds very different from a pickup wound with less wire in that the low end has a distinctive thickness about it.

[Marko Ursin]

So you'd say that Wal style humbucker and a traditional humbucker wound around same size steel poles as Wal to same resistance with same magnets would sound quite the same?
Marko

[Mike Sulzer]

Not exactly. it would be very hard to get both the same resistance and the same number of turns. And even if you did, the inductances would still not be quite the same. But the choice of individual coils in series, or a single large coil, is not one that makes a significant difference in my experience as long as you connect up the two units in the same way. But David S. is correct that I have not tried it with this specific pickup. I am surprised that he hears a large difference.

So you'd say that Wal style humbucker and a traditional humbucker wound around same size steel poles as Wal to same resistance with same magnets would sound quite the same?
Marko

[David Schwab]

Steel: Where it is matters. A heavy keeper outside the coil has a lot less effect than steel in the core, as far as inductance is concderned So I think the mudbucker with its large core really has effectively much more steel.

Who says the mudbucker has a large core? Do you know what's in a mudbucker? Then you can take the exact same design, wind it with less wire, and end up with a very bright Gibson Bi-Centenial Thunderbird pickup. The only difference between the two is the amount of wire on the bobbins. Most of the steel in a mudbucker is between the two bobbins (the keeper). The core of the bobbins is a 1/16" thick piece of steel.

Also, if you remove the keepers from the Wal pickup, it sounds different. It lacks a little low end warmth. Marco tried this with one of his versions. Anytime you put a piece of steel close to a pickup the inductance changes a bit.

Also the area of the steel core is much greater in the mudder, and the higher voltage around that path drives eddy currents more effectively. So you move the resonance down in frequency with a high inductance, and then damp it with eddy currents, and you are left with mostly bass. This is why I think you cannot really compare the Wal and the mud pie by looking at just resistances.

OK, we will take another example. The old Guild bass humbucker. It's built pretty much like a conventional humbucker and reads about 35k. It sounds pretty much like the Gibson mudbucker. It uses thinner wire because the bobbins are smaller than the Gibson pickup. The Guild pickup would be a good analogy to the Wal, since it uses screw and studs for the poles, and has a similar amount of steel.



It is a clear fact that winding more wire on a pickup makes the tone dark. We have many real world examples of this. Winding the same amount of wire on multiple smaller coils does not darken the tone.

[Marko Ursin]

Not exactly. it would be very hard to get both the same resistance and the same number of turns. And even if you did, the inductances would still not be quite the same. But the choice of individual coils in series, or a single large coil, is not one that makes a significant difference in my experience as long as you connect up the two units in the same way. But David S. is correct that I have not tried it with this specific pickup. I am surprised that he hears a large difference.

So can I say that when making pickups with different coil arrangement they sound different? Isn't that exactly why we make different pickups? I've made these multicoil pickups in at least 5 different resistance and with different pole-magnet combination and they sound always somehow similar and different from similar singlecoil or humbucker.
Marko

[Steve Conner]

It is a clear fact that winding more wire on a pickup makes the tone dark. We have many real world examples of this. Winding the same amount of wire on multiple smaller coils does not darken the tone.

There is a proper scientific reason for that. Inductance goes up as the square of the number of turns, but only if the turns are magnetically coupled together. In other words, if they're all on the same coil. For independent coils the relation is linear: take 5 coils the same and hook them in series, and the inductance will be 5 times the value for a single coil, not 25.

So, if you take a bazillion feet of wire and make one big coil, it'll have more inductance than if you made several small ones from the same length of wire. And, more inductance means a darker tone.

I guess some of the pickup physicists might quibble with this. Air cored coils don't quite obey the square law, because the coupling between turns isn't perfect even if they're all on the same coil. And, there will always be some coupling between multiple coils when they're mounted side by side in a pickup.

But I think the argument is still qualitatively valid.

[Mike Sulzer]

The law works perfectly for air core coills. The fact that the coupling is not perfect is irrelevant, because it remains constant. Remember the law requires that the coil geometry remain constant as you change the number of turns. It also applies pretty well to a high permeability closed core, and the geometry does not matter because nearly all the flux is contained in the core.

I think your first paragraph deals with the wrong problem. When we take the big coil and divide it up into five smaller coils, each of the smaller coils has the same number of turns as the original one, not one fifth, because each coil is smaller and takes about one fifth the wire for the same number of turns. If the five smaller coils have a fifth of the steel, or something similar, then we expect each to have a fifth of the inductance, roughly speaking*. (This was the point of the Bartolini patent David mentioned.) But if we put the the five in series the inductance should be similar to the original coil.

If "darkness" is related to inductance, they should be nearly the same single or five in series. David says no, but I am unconvinced.

So, making individual small coils and amplifying each separately can give very wide bandwidth (if that is what you want), but putting them back in series should not.

*Inductance formulas are complicated. Remember that for an air core single layer solenoid:


d is the diameter, z is the length. For a short coil, the d in the denominator cancels one of those in the numerator, and the inductance depends on the dimension linearly, not with the square. So if you were to use the same total amount of wire as a single large short solenoid, or several small ones, and put them in series (far enough apart to not couple), you get the same total inductance. (Think of a single turn coil first, then generalize.) It gets more complicated to understand longer coils!

There is a proper scientific reason for that. Inductance goes up as the square of the number of turns, but only if the turns are magnetically coupled together. In other words, if they're all on the same coil. For independent coils the relation is linear: take 5 coils the same and hook them in series, and the inductance will be 5 times the value for a single coil, not 25.

So, if you take a bazillion feet of wire and make one big coil, it'll have more inductance than if you made several small ones from the same length of wire. And, more inductance means a darker tone.

I guess some of the pickup physicists might quibble with this. Air cored coils don't quite obey the square law, because the coupling between turns isn't perfect even if they're all on the same coil. And, there will always be some coupling between multiple coils when they're mounted side by side in a pickup.

But I think the argument is still qualitatively valid.