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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.
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Annotation:
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If the strings are steel, they'll acquire permanent magnetism from moving in a magnetic field. |
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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). |
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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. |
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Quite what effect this might have is unclear, and is in all likelihood not worth investigating beyond a thought experiment. |
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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. |
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// . I've never noticed if they become magnetic // |
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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. |
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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. |
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This would allow the use of non-magnetic strings in an electric guitar ... |
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But the strings would be at above-ground Voltage while
running over grounded metal hardware. |
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Yes, that had ocurred to us. The electric guitar operator might well receive a painful, possibly fatal, shock ... |
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... so really, there's no downside. Think of the saving in earplugs. |
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Next, how about a system for electrocuting drummers ? Yadda, yadda, ha-ha cruelty to dumb animals ... but they do need to be culled. |
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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. |
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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. |
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Superconductive strings are the answer. Or maybe a
complicated tuning compensator. Or go with no
strings at all towards a thereamin... |
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