Individual coil 5-string pickup; how do I wire it?

[Marko Ursin]

I'm planning to make an individual coil 5-string pickup using 5 similar coils as I used on the Wal-inspired pickup a while ago. How do I wire them to make the pickup hum-cancelling? Is it just simply 3 and 2 coils in series and these two groups in series, different polarity on magnets on each group and start and end reversed on the other group? I'm planning to use only one pickup so I can't make two different polarity/different clockwise pickups.
Marko

[Bruce Johnson]

Just wire them all in series, with two of them being reverse winding (reversing the terminal connections) AND reversed polarity magnets. That's how I do my individual-coil-per-string pickups. Although the 5-string group isn't truly mirrored for humbucking purposes, in my experience, I haven't been able to hear any significant difference in hum between the 5-string and 4-string groups.

[David King]

Marko if you want to get closer to common mode rejection you could make a sixth coil that you can tuck away inside the control cavity. It doesn't need to have the magnet magnetized and probably doesn't even need a magnet at all to cancel correctly. Another option is to make the two coils fatter, either with larger area inside the coil or more turns of wire so that the total turns of the N-up pickups = the total turns of the S-up. There are some obvious issues with doing either of those things, a larger area coil will have turns further away from the magnets and will sound much less bright. Adding 33% more turns will upset the output balance so you would need magnets that are less strong to even things out. The noise of a 3:2 coils PU will be the same as a single coil.

[David Schwab]

If you do wind two coils with more turns, maybe you can stick them under the treble strings to fatten them up.

[Dave Kerr]

The noise of a 3:2 coils PU will be the same as a single coil.

If the number of turns is the same, wouldn't you expect the noise to be quite a bit less than with a single coil due to the reduced area of the single string coil? I like the idea of increasing the average area of the turns of the 2 coils, just build the core up with a couple wraps of tape, maybe use heavy build wire as well, wind 5% or so more turns on the 2 coils - do all of these and the small incremental adjustments can add up.
edit - plus do what David S says above for those slightly hotter coils

[David King]

Dave Kerr,
I agree that a single string coil will have less induced noise than a wide, 5 string coil. That's all I'm saying above, the 4 coils cancel out and leave the 5th coil hanging. It should be 20-25% of the total induced noise of a long single coil and that may be good enough for Marko.

[David Schwab]

The noise of a 3:2 coils PU will be the same as a single coil.

That's not true. It might not be 100% hum cancelation, but it will be quieter than a single coil. I have an old Bartolini Hi-A pickups that uses mismatched winds on the two coils. They use the same gauge wire. One coil is 4.62K, and the other is 3.4K It's dead quiet.

What I would do is find the optimum wind for the 2 coils, and then decrease the winds on the other three slightly less than the amount to match the two coils.

[Bruce Johnson]

That's not true. It might not be 100% hum cancelation, but it will be quieter than a single coil. I have an old Bartolini Hi-A pickups that uses mismatched winds on the two coils. They use the same gauge wire. One coil is 4.62K, and the other is 3.4K It's dead quiet.

What I would do is find the optimum wind for the 2 coils, and then decrease the winds on the other three slightly less than the amount to match the two coils.

From my own experience, I couldn't hear any increase in hum of the 5-string (3+2) over the 4-string (2+2). I had 4-string and 5-string basses side by side, both using the same spec modular coils. Holding them against flourescent lamps and amps, both were equally quiet. Maybe you could measure something with meters, but I couldn't hear it. For reference, I had previously tested groups of 4 and 5 modular coils all wired in series, same direction, same magnets. Those were definitely noisy against the same sources. So, there's no question that the humbucking configuration works. And, to my testing, the 3:2 imperfect humbucker was close enough to the perfect 2:2 humbucker to not be worth fussing over.

As a side note, I sent a customer a group of 5 of my modular pickups, in the 3:2 humbucker configuration, and included a 6th dummy coil. The dummy coil was exactly like the others but without the magnets. The idea being to make a pure 3:3 humbucker. Well, he tried the system with and without the dummy coil, and couldn't tell any difference (other than the slight tone shift from the added resistance).

I just report the results.

[Dave Kerr]

Dave Kerr,
I agree that a single string coil will have less induced noise than a wide, 5 string coil. That's all I'm saying above, the 4 coils cancel out and leave the 5th coil hanging. It should be 20-25% of the total induced noise of a long single coil and that may be good enough for Marko.

Don't know how I misread/misunderstood your remark, in context the "single coil" was certainly one of the 5 coils, not a conventional single coil pickup.

[David Schwab]

the 4 coils cancel out and leave the 5th coil hanging.

No, it's three coils against two coils. So it's a mismatched humbucker. Even if you wired four of the coils up like a humbucker, the fifth coil is going to match one side or the other, so then you have three against two.

[Marko Ursin]

Thanks for the replies once again. I think I'm going to make 6 coils and try with/without the dummy coil.
Marko

[David King]

No, it's three coils against two coils. So it's a mismatched humbucker. Even if you wired four of the coils up like a humbucker, the fifth coil is going to match one side or the other, so then you have three against two.

David, I can't argue with that, I think we are essentially saying the same thing -there will be some induced noise but not very much.

[Marko Ursin]

Just to make sure is this correct way to wire this kind of pickup to make it humbucking? Coils 1, 2, and 3 have S polarity up, 4 and 5 have N up. All coils are wound clockwise, black wire is start and blue wire end of each coil. 6th coil will be in the control cavity. Hot and ground are the two blue wires on each side of the pickup.

Marko

[David King]

Marko,

That looks like it should work to me. I always find it easier to try first and rewire until I get it right though in this case there are probably many correct ways to wire it since it's the only pickup on the bass. If you notice a jump in volume between the adjacent N-S poles you might consider alternating the N and S poles S-N-S-N-S so that any cancellation could be equalized across all the strings instead of just two of them, the A and D strings .

[Bruce Johnson]

Yes, I agree with David. I would make #2 and #4 the N-up coils, with their leads connected opposite. Then the #6 dummy coil, if you use it, would be at the end with its connections the same as #2 & #4.

The bigger reason for alternating the coils like that is to even out the shape and strength of the magnetic fields from string to string. Think about how the magnetic field from each coil will be affected by its neighbor. As you have it assembled above, #2 would be more powerful than the other four.