Wider coils than Jazzmaster pickups?

[rjb]

If by wider you mean perpendicular across the strings, you can't get much wider than this configuration by Bruce Johnson.

Too late to edit...
Meant to say "If by wider you mean along the strings", or something like that.
But you-all can tell what I meant by the pic.

-rb

[big_teee]

Too late to edit...
Meant to say "If by wider you mean along the strings", or something like that.
But you-all can tell what I meant by the pic.

-rb

The Bruce Johnson coils don't appear to be one wide coil.
I think they are 4 skinny coils turned sideways!
T

[rjb]

The Bruce Johnson coils don't appear to be one wide coil.
I think they are 4 skinny coils turned sideways!

Of course they are. That's why I referred to a "configuration".
I'm not sure why epizootics wants to experiment with *really* wide coils - but if the goal is to sample a long section of the string, this is an alternate way of achieving that goal.

-rb

[Jason Rodgers]

It makes sense to review how a pickup works in order to understand when a wider coil would have the kind of effects you are interested in.

1. The permanent magnetic field from the pole pieces magnetizes the strings. Right over the pole pieces, the field from this string magnetization points towards the pole pieces. The string magnetization becomes weaker further from the pole pieces along the strings, and it increasingly points along the string rather than towards the pole piece.

2. A turn of wire in the coil produces a voltage that depends on the time varying field from the magnetized vibrating string, but it is only field lines that pass through the loop that count. Furthermore, it is only the component of the field that is perpendicular to the plane of the loop that counts. So the field from the part of the string over the pole piece is very effective since it is strong and points through the coil. But the field from a part of the string that is farther away is both weaker and it points less directly through the coil because the magnetization points more along the string.

3. When you wind more wire on a coil, whether it is by making the coil wider or deeper, you increase the inductance, making the resonant frequency lower, and the resistance, making the resonant peak broader and less high.

4. When you make a coil wider, the turns near the outside enclose the magnetic field from the part of the string over the pole piece just as the turns near the pole pieces do. However, the additional field that the outer turns enclose (from the parts of the string further away from the pole piece) do not add much.

5. If you made the coil very wide, you would get almost nothing. This is because magnetic field lines have no beginning or end. So a field line from the vibrating string that passes directly through the coil loops back to the string. A wide enough coil would enclose this line twice, once in each direction, and so its effect would cancel out.

6. A narrow strat pickup gets nearly all of the field from the most effective part of the string. A wider pickup sees this field more times (because it has more turns), but gets very little voltage from the additional parts of the string that are sampled because these parts are weakly magnetized, and the field mostly points in the wrong direction.

7. You can use information such as this to guide experimentation, but the exact sound you get is only learned by winding it and listening.

Question on your #6- Let's say we made one of those hybrid, P-90-ish pickups that's basically a Strat pickup with A2 or A5 rods and 1/4" between the flats. So now you have a pickup with a wider, shorter coil, but same wind count at 9000-10,000 and same DCR. Does it sound warmer because a lower voltage is being created and that lower voltage truncates the frequency spectrum?

[Mike Sulzer]

Question on your #6- Let's say we made one of those hybrid, P-90-ish pickups that's basically a Strat pickup with A2 or A5 rods and 1/4" between the flats. So now you have a pickup with a wider, shorter coil, but same wind count at 9000-10,000 and same DCR. Does it sound warmer because a lower voltage is being created and that lower voltage truncates the frequency spectrum?

The short approximate an answer is that the wider shorter coil has a higher inductance, and thus a lower resonant frequency. The slightly longer answer is that if you use the same number of turns and keep the wire size the same, then the dc resistance increases (longer average turn length), making the peak broader and lower. Predicting the exact inductance of coils in pickup shapes is hard. Even with an air core, it is not so easy, but with some magnetic material in the core it gets even harder.

One simple thing to remember is that if you have a single turn coil, the bigger you make it, the higher the inductance. Another thing is that in a multi turn coil, the turns interact, making the inductance higher than you might expect if you just counted the number of turns. Also, in a wide flat multi turn coil, the turns interact more than in a tall coil of the same number of turns. But these are just approximations. And it is hard in experimenting with pickups to change just one factor.

[Alberto]

Theory aside, experimenting with 0,3'' between the flats, strat alnico rods and same turns of awg42 wire, I get warmer sounding pickups.

[Jason Rodgers]

Theory aside, experimenting with 0,3'' between the flats, strat alnico rods and same turns of awg42 wire, I get warmer sounding pickups.

Yeah, I did this with A2 rods and 3/8" between the flats. Just wondering what the theory behind it was.