Electronic music - pickups

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Piezo elements

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

A piezo element (often in disc form, sometimes in others like a guitar pickup's rectangular pellets) responds to bending/stress on its surface with voltage.

This makes them useful to sense vibration (including sound), impact (they are common in electronic drumkits), and in theory sense something bending, though there are more robust ways to do that.

There are piezo-based kinetic switches - e.g. battery-less RF buttons that operate from the energy you put in.

You can also use them as actuators, but only for very small movement - small sounds, small actuators in microscopy, maybe some haptic feedback.

(They are seen in some vandal proof buttons, because there can be a serious amount of hard material in between button and piezo. Yet they are not the only or often even best way to do that.)

On piezo polarisation

Electromagnetic pickups

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Electromagnetic pickups, a.k.a. magnetic pickups, means

• a coil,
• close to a permanent magnet (practically often inside the coil, it's useful positioning),
• with both oriented and positioned so that a nearby conductor moving in that field affects the field in a way that makes it into the coils pretty efficiently

For context: When you move a magnet near a wire, current flows. This is e.g. how an electric generator works, turning movement into electricity.

A guitar does something similar.

You might think that instead of moving the magnet near a wire, it moves the wire near a magnet. That's closer but not quite it, because while magnetic strings would work, that would be hard to make.

The magnet is there to set up a field strong enough for the coils to then notice the variation in. Inside that ever-present magnetic field, any moving conductor would disturb that magnetic field - and thereby what the coil picks up.

So the vibrations of the string becomes the signal on the coil. With some extra steps.

This is also why such guitar pickups only work with metal strings, and do not pick up anything acoustic, so the rest of the guitar's design barely matters to the sound - except perhaps to things like

hitting the body (impacts end up soft vibration of the strings),

sympathetic vibration of strings

shaking a guitar

Single coil or humbucker

Coils are by nature an antenna.

For the magnetic field in the same pickup, but also for any other strong-enough EM happening closeby.

The strongest of which is usually the 50Hz or 60Hz power hum.

.

It will pick up anything that produces lower frequencies. You largest saving grace is distance - an inverse square thing.

Say, put an electric screwdriver/drill next to it and you'll hear its motor, but move it away and it easily falls below other noise.

Actually anything digital. even if the communication is at a much higher frequency, particularly digital transmission tends to be low -- and that 'sending or not'

E.g. the The elektrosluch lets you record baseband EM as sound -- and is nothing more than a coil and an amplifier.

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The simplest pickup is a single-coil pickup, which don't address this at all. There are some ways to reduce hum (e.g. don't be near a powered object), but not by a lot.

People then thought up humbuckers, a setup that takes

• two such coils,
• hooked up in opposite polarity,
• and one with its magnets flipped.

This is a clever trick, but it involves two parts, so if you want to actually understand them, you probably want to work this out on paper.

Due to picking up equally and being hooked up opposite, anything that both coils in the pickup receive the exact same amount ends up being subtracted.

Okay, well, why do the strings still get picked up then?

That's where the other part comes in: due to one coil having its magnets flipped,

the signal that the coils pick up from the strings is the same but flipped,

the signal that the coils pick up from the environment is still the same.

Subtract the two, and

the string signal is subtracted from a flipped version and becomes twice as strong (the magnitude doesn't matter, that's part of the design)

the environment noise in both is a near-copy so mostly substracted,

That environment-noise subtraction is far from perfect for a few reasons (e.g. the fact that the coils cannot be in entirely the same place), but it works out pretty decent for lower frequencies, and for sources that are further away.

Mains hum is usually both, so humbuckers work pretty well.

Technically, you can connect humbuckers either in series or in parallel, but series is more typical due to the output signal (and the hum-reducing effect(verify)) being a little stronger.

Single coils tend to work out a little brighter (and used in surf, sixties sounds), humbuckers tend to be bassier.

And then there are distinct designs of both, so they're each more like small design families.

Sustainers

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

A guitar sustainer is an electromagnetic pickup coil, plus amplifier and driver coil.

It sends out what it receives (due to typical design largely focuses on lower frequencies), which on a guitar amounts to forcedly resonating the tone currently being played.

Sustainers are often sold as separate products.

Some guitars have sustainers built in (this is often custom), which will often look like regular pickups, and could even be used as a pickup when not active, should you want to.

Sustainers are often used for spacey sounds or other genre-specific things, because while it's good at controlling slow volume swells, tremolo, and some other expressiveness that you otherwise cannot easily do on guitars (and are more commonly associated with other instruments, like violins - which is e.g. where the e-bow gets its name), the same long sustains don't combine too well with strumming or fast playing.

The E-bow is one brand of hand-held sustainer, aimed to work on one string, to add expressiveness to phrasing. It has grooves to the side to rest on other strings you're not playing, and indicates where it most picks up and excites.

Its designer found that if you reverse the driver coil, it dampens the fundamental frequency and amplifies overtones/harmonics a bit more. This is presumably all that the harmonics switch does.