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A Pickup Thought (electromagnet Pole Pieces)


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After working as an engineer for the last while, this topic finally gets me back to my physicist roots. So in the P-Rails thread, there was some discussion about how having two pickup coils next to each other will always alter the sound of each coil relative to it being in it's own space. Now, the real reason for this is because we are using permanent magnets as our pole pieces and at the pickup base (don't respond yet, read the rest of the post).

So here is my thought, if we could have two coils next to each other that have pole pieces and baseplates that aren't permanent magnets, we could, in theory, have two coils next to each other that would sound probably very similar to what they would sound like if physically separated a "large" distance. Now, I know there are a whole lot of logistics to be sorted out with it, but that is not so much what I am interested in at this point. My question is more along the lines of "What if we were to use electromagnets as the pole pieces and base magnet and only activate the magnets in the coils we want to use?" I know this would most likely sound very different from a traditional pickup because of the difference in the magnet properties created, but from a purely fundamental standpoint, it seems like it would work.

Now, I know that the physical presence of the other coil will have some effect, regardless of whether or not the pole pieces are magnetic at the moment or not, but that is a different debate.

Any thoughts regarding the issue? I know that this would involve either batteries or phantom power, extremely small electromagnets, more complex switching schemes, and on and on. But I'm just interested to hear what thoughts others may have had.

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An interesting idea - to replace the magnet slugs with little electromagnets. But really - I think the effect you are trying to avoid (fringing fields from nearby magnets) are a small part of the overall equation. Try this as a test - play a single-coil guitar through only one pickup, then stick a thin 3" long bar magnet next to the coil (under the strings) and play it again - and see if you can hear an audible difference.

Only issue I see is that you need a lot of current to generate the right amount of magnetic field from each electromagnet. My guess is that the current requirements may be more than is typically provided by phantom power (certainly more than you can get from any battery of the size that will fit in a guitar body).

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but from a purely fundamental standpoint, it seems like it would work.

Assuming you can get around the current requirements, the need for a very clean power source (any slight noise will be overwhelming in the pickups output signal), and the physical bulk of the coils for your electromagnets, what about the properties of the transformer you will have just created that is generating meltingly large voltages in your pickup coil ?

Edited by col
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