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Variable Strength Electromagnetic Pickup

Use a powered second coil to vary field strength.
  [vote for,

The electric guitar pickup is a simple device. Take a permanent magnet, wrap a load of insulated wire around it and connect the ends to an amplifier. Now, if you wobble the steel-cored string near it, you get a wobble in the magnetic field and thanks to Faraday you get an electric wobble down the cable to the amp. The amp makes the wobble more robust and passes it to a speaker, which is sort of a big pickup in reverse.

To change the nature of the pickup, you can vary a few things. You can wind more or less wire, you can move the whole thing relative to the strings and you can vary the magnet strength. Typically, pickup magnets are old tech. AlNiCo magnets from the tone mines of West Texas marinaded in delta mud, their strength is low and fixed at manufacture. More powerful ceramic magnets are occasionally used to increase efficiency and therefore gain what for making more offensive music.

Instead of a permanent magnet, I suggest a soft iron core with two coils. The outer coil is the standard pickup winding. The inner coil is simply connected to a VERY DC power supply that can be varied by a pot on the guitar. In this way you can change the characteristics of the pickup at will, this is useful because sometimes you run out of excuses for your crappy tone.

bs0u0155, Nov 08 2018

Homemade electric guitar https://www.youtube...watch?v=TwIvUbOhcKE
[bigsleep, Nov 10 2018]

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       If the strings are steel, they'll acquire permanent magnetism from moving in a magnetic field.   

       Since your bias coil is an electromagnet, its polarity can be arbitrarily reversed by the "player" (we do not consider that the word "musician" is appropriate for the user of an electric guitar).   

       Depending on their magnetic polarity, strings will be attracted or repelled. If strings have inconsistent polarities, some will be pushed away, some drawn closer to the pickup.   

       Quite what effect this might have is unclear, and is in all likelihood not worth investigating beyond a thought experiment.
8th of 7, Nov 08 2018

       Pickup magnets do have effects on strings. I've never noticed if they become magnetic, or even if the steel core is the main component of input. Typically there is a much thicker nickel winding around it. What does happen with beefy pickups is that they drag the strings toward them changing the action a little. It all gets a bit non linear and annoying when setting string/pickup height as they get all interacty.
bs0u0155, Nov 09 2018

       // . I've never noticed if they become magnetic //   

       Well, a snapped string would be an occasion to fish out that Christmas-cracker compass that's been in your bedside cabinet all year and see if you get any deflection from remanent magnetism.   

       If a current were passed through the strings, that would generate a magnetic field. A pickup coil could then detect the induced current when the string oscillated, without needing a fixed magnet.   

       This would allow the use of non-magnetic strings in an electric guitar ...
8th of 7, Nov 09 2018

       But the strings would be at above-ground Voltage while running over grounded metal hardware.
bs0u0155, Nov 09 2018


       Yes, that had ocurred to us. The electric guitar operator might well receive a painful, possibly fatal, shock ...   

       ... so really, there's no downside. Think of the saving in earplugs.   

       Next, how about a system for electrocuting drummers ? Yadda, yadda, ha-ha cruelty to dumb animals ... but they do need to be culled.
8th of 7, Nov 09 2018

       Actually, that's not a terrible idea. You could put some kind of insulation on the strings (as is done with electrical wiring generally), or use an independent constant-current supply at the bridge for each string, and not care how far along the neck each string gets grounded. The strings might get hot, though.
notexactly, Nov 11 2018

       If the strings get hot, they'll expand, changing the tension and hence the tuning. So the current needs to be small enough that the heating effect isn't significant.
8th of 7, Nov 11 2018

       Superconductive strings are the answer. Or maybe a complicated tuning compensator. Or go with no strings at all towards a thereamin...
RayfordSteele, Nov 11 2018


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