Single Coil with Humbucking Effect

[eblock]

Need some help understanding how to construct a noise canceling single coil type p/up:

1. If I wanted to construct a p90-type p/up for this, would it consist of basically making a traditional style p90 and then attaching another coil, wound in same direction (without magnets) to the baseplate- where the baseplate is essentially sandwiched between the coils and then connecting the ends of the two coils windings and making the beginning leads?

2. Using a strat-type p/up- if I wound three of the magnets with a coil and the other three with another, separate coil (both wound same direction and ends connected with beginnings leads) would the magnets in one coil need to be opposite or same polarity as those in the other?

Sorry if these are idiotic questions...still very new to this and trying to understand.

[black_labb]

why not do something like the split pickupos they use on fender basses. its prettymuch a humbucker with 3 pole pieces on each side. not sure how easily you would be able to put them right next to eachother.

[eblock]

I think that might be what I'm thinking, but just not sure on the polarity of the three pole pieces- are all 6 same polarity or three south and the other three north?

[Sock Puppet]

http://music-electronics-forum.com/s...ght=split+coil

http://www.curtisnovak.com/pickups/r...at/index.shtml

[eblock]

Sock Puppet- the curtisnovak link answered my question. Thank you.

[Possum]

not perfect...

The Novak pickup and others like it have a fault, being the middle two pole pieces where the coils split, there is a phasing problem. Make one and you will hear it. this is why these kinds of pickups never became commercially successful...

[Mark Hammer]

I gather the Z design on the G&L Will Ray model pickups is intended to get a bit past that. Obviously the same strings (D and G) are still in the same proximity to the opposite side polepiece, but whatever wackiness the magnets induce when configured as in the posted Curtis Novak picture (identical to the old Evans Eliminator pickups, but for the end-shape of the bobbins) is presumably reduced a bit by having the two coils offset a bit from each other, as in a Precision bass.

[David Schwab]

Need some help understanding how to construct a noise canceling single coil type p/up:

1. If I wanted to construct a p90-type p/up for this, would it consist of basically making a traditional style p90 and then attaching another coil, wound in same direction (without magnets) to the baseplate- where the baseplate is essentially sandwiched between the coils and then connecting the ends of the two coils windings and making the beginning leads?

That could work... having the baseplate between the coils is a good idea. You wire the two coils out of phase with each other, and you want to limit how much of the strings the bottom coil pickups up, because they will sound thin otherwise. You probably should put some pole pieces (but no magnets) in the bottom coil to increase the inductance, but you don't have to. You want to try and shield the bottom coil from the magnets as well. having some kind of ferric metal in between helps.

2. Using a strat-type p/up- if I wound three of the magnets with a coil and the other three with another, separate coil (both wound same direction and ends connected with beginnings leads) would the magnets in one coil need to be opposite or same polarity as those in the other?

The way a humbucker works is you have two coils wound out of phase. Electrical interference is picked up by both coils, and when their outputs are summed, the hum gets canceled out.

The reason the strings don't cancel (fully, there's always some cancelation with gibson style humbuckers) is because each coil has the opposite magnet polarity, so they each sense the strings with an opposite phase relationship.

In the case of a split pickup, like a P bass, you don't have to have the magnets opposite, since no string is picked up by both coils. But there's always an out of phase thing going on. As Possum said, they don't work that great compared to stacked and dual coil types. If you overlap the coils as on a P bass they work better, but it's hard to get that in a Strat size case.

[Dave Kerr]

Might the baseplate shield the lower coil from much of the RF interference the upper coil senses?

[David Schwab]

Might the baseplate shield the lower coil from much of the RF interference the upper coil senses?

It might. Some of these designs with the shields under the upper coil have the shield extending to the lower coils core to transfer the interference.

[eblock]

That could work... having the baseplate between the coils is a good idea. You wire the two coils out of phase with each other, and you want to limit how much of the strings the bottom coil pickups up, because they will sound thin otherwise. You probably should put some pole pieces (but no magnets) in the bottom coil to increase the inductance, but you don't have to. You want to try and shield the bottom coil from the magnets as well. having some kind of ferric metal in between helps.



The way a humbucker works is you have two coils wound out of phase. Electrical interference is picked up by both coils, and when their outputs are summed, the hum gets canceled out.

The reason the strings don't cancel (fully, there's always some cancelation with gibson style humbuckers) is because each coil has the opposite magnet polarity, so they each sense the strings with an opposite phase relationship.

In the case of a split pickup, like a P bass, you don't have to have the magnets opposite, since no string is picked up by both coils. But there's always an out of phase thing going on. As Possum said, they don't work that great compared to stacked and dual coil types. If you overlap the coils as on a P bass they work better, but it's hard to get that in a Strat size case.

Not sure I understand how limiting how much of the strings the bottom coil picks up, would make them sound thin? Wouldn't whatever is picked up by the bottom coil just add to the primary coil's signal? Also don't understand how putting pole pieces in the bottom coil, but no magnets would increase inductance?

[David Schwab]

Not sure I understand how limiting how much of the strings the bottom coil picks up, would make them sound thin? Wouldn't whatever is picked up by the bottom coil just add to the primary coil's signal?

No they will subtract from one another! They are out of phase. If you can keep the bottom coil from sensing the strings the low end wont get canceled out. In a side by side humbucker, each coil has opposite magnetic polarity, which adds the signals when the two out of phase coils are summed. Electrical interference enters the coils with the same phase, and is canceled out when summed.

Also don't understand how putting pole pieces in the bottom coil, but no magnets would increase inductance?

Because metal cores increase inductance in a coil. If you have no cores, it's an air coil, and will have low inductance. You can add magnets, but then the bottom coil will act like a pickup, which is not what you want.

Also if you increase the inductance enough, you can use a smaller coil.

Some designs have the magnets running though both coils.. Duncan does this. The idea here is each pole is far enough away from the other so that the signal doesn't cancel.

You will notice that a lot of stacked pickups have a high DC resistance, presumably to keep the tone from being thin and weak.

[eblock]

Ok, thank you. I think was confused in that I thought the second coil's only purpose, by being electrically out of phase with the primary coil, was to cancel (only) noise from the primary coil. Also, I'm still not sure how non-magnetized metal cores would increase inductance- thought inductance in a coil could only take place in the presence of a magnetic field. I think I'm maybe going wrong thinking of this as being the same as removing the pole pieces from one bobbin in a humbucker, only the two coils are stacked rather than side-by-side.

[David Schwab]

Ok, thank you. I think was confused in that I thought the second coil's only purpose, by being electrically out of phase with the primary coil, was to cancel (only) noise from the primary coil. Also, I'm still not sure how non-magnetized metal cores would increase inductance- thought inductance in a coil could only take place in the presence of a magnetic field.

Well there's magnetic inductance, which is how the current gets in the coil... but think of an inductor (choke) coil. No magnet. Having the metal in the dummy coil will increase it's sensitivity to noise.

I think I'm maybe going wrong thinking of this as being the same as removing the pole pieces from one bobbin in a humbucker, only the two coils are stacked rather than side-by-side.

With a side-by-side humbucker, the second coil is still in the magnetic circuit, although removing the poles would lessen it's sensitivity to the strings. You'll notice most of the stacked humbuckers have a magnetic shield between the coils.

An interesting thing to try would be use rod magnets in the one coil, and either just slugs or nothing in the other.

[Tonerider]

I gather the Z design on the G&L Will Ray model pickups is intended to get a bit past that. Obviously the same strings (D and G) are still in the same proximity to the opposite side polepiece, but whatever wackiness the magnets induce when configured as in the posted Curtis Novaks picture (identical to the old Evans Eliminator pickups, but for the end-shape of the bobbins) is presumably reduced a bit by having the two coils offset a bit from each other, as in a Precision bass.

The Evans Eliminator pickups had two configurations, one for the neck and middle pickups and one for the bridge. The neck and middle pickups had overlapping coils on the G and D string. Tiny coils on tiny neo magnets. Like this

OOOO- -
- -OOOO

The bridge was similar to the Novaks with larger magnets

OOO-OOO

Curtis's design is solid but only good for a bridge pickup where the G-string is hard to bend (impossible?) over the centreline with the D pole.