Magnet mixtures?

[Fluoroscope 5000]

Thanks for addressing this, everyone. Clearly, I don't know much about the physics. I've tried to qualify my "theories" accordingly. If my questions/statements instigated clarification by qualified professionals, than perhaps I've served a purpose.

Great to see the tests DS did with different magnets and blades. I guess my idea about field ripples is wrong, but if the bottom and top of the blade have very different Gauss levels, I'd think that would cause some odd behavior in the coil. In any case, I think it useful to know how much the blades can take before saturation.

[David Schwab]

but if the bottom and top of the blade have very different Gauss levels, I'd think that would cause some odd behavior in the coil.

There's a lot of odd stuff, like what is the outside of the coil doing in comparison to the inside? How about the top of the coil vs the bottom? If you make a stacked pickup, and switch the two coils in and out, you can hear that the top is loud and bright, and the bottom is darker and mellow. In the end we hear a composite of what ever various parts of the coil are doing.

We have long speculated on these things here, and people like Joe, Mike and Daniel (salvarsan) give good insight into some of the physics involved. In the end, you have to find what works for the tone you want. You cab base that on science, or at least what we know about the complex nature of pickups, and that's a good starting point. But it wont always get you 100% there yet, IMO. Sometimes trail and error works well too.

[bbsailor]

There's a lot of odd stuff, like what is the outside of the coil doing in comparison to the inside? How about the top of the coil vs the bottom? If you make a stacked pickup, and switch the two coils in and out, you can hear that the top is loud and bright, and the bottom is darker and mellow. In the end we hear a composite of what ever various parts of the coil are doing.

We have long speculated on these things here, and people like Joe, Mike and Daniel (salvarsan) give good insight into some of the physics involved. In the end, you have to find what works for the tone you want. You cab base that on science, or at least what we know about the complex nature of pickups, and that's a good starting point. But it wont always get you 100% there yet, IMO. Sometimes trail and error works well too.

David,

You are correct about the consequence or the wire coil being near the center of the magnet vice being farther out or being lower. I call this "pickup coil wire zones".

Here is a crude text drawing (pickup side view) to depict what I have discovered in making single-loop current driven pickups using current transformers.


Zone2 Zone1 I M I Zone1 Zone2

Zone4 Zone3 I M I Zone3 Zone4

M = Magnet

I have listed the zones in the order of the highest output with Zone1 being in the strongest magnetic field and also being closer to the strings while Zone4 has the lowest output. This may account for why Alumitone current-based pickups tend to sound brighter because the single loop coil is near the magnet and near the strings. This leads to some speculation about whether the .125 inch thick alumium frame, being the primary string loop, may have eddy currents being generated in so as to reduce the ability to detect upper harmonics a little better. AWG litz wire 28 stranding is recommended for 60Hz to 1KHz; AWG 30 for 1KHz to 10KHz; and AWG 33 for 10KHz to 20KHz. http://www.litzwire.com/litz_design.htm

I would be interested in hearing if you agree with my ranking of the priority of the wire zones as they relate to output.

This observation about using Litz wire in the primary coil string loop may be something that the Alumitone folks might want to tinker with for the next generation of current-based pickups.

Joseph Rogowski

[David Schwab]

Joseph, sorry for the delay answering this. I hadn't had power for a week from hurricane sandy, and then did't see this thread.

Yeah, I think what you are saying makes sense. I have not tried listening to inside vs. outside of coils, but that's what I would imagine is going on.