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 around, 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

When you move a magnet near a wire, current flows. This is how an electical generator works, turning movement into electricity.

A guitar does something similar, but instead of moving the magnet, it moves the wire very near a magnet.

It's not that the strings are magnetic, it's that the pickup has two distinct parts: magnets, and a coil. The magnet is there to set up a field strong enough for the coils to then notice the variation in it.

In that setup, the vibrations of the string becomes the signal on the coil, fairly directly.

This is 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), shaking the guitar (varying the strings's vibration enough to work out as vibrato).

Single coil or humbucker

Coils are by nature an antenna.

That makes them good at picking up any electromagnetism happening nearby, the strongest of which is usually the 50Hz / 60Hz power hum.

And this hum can be made more noticeable by certain audio effects, including distortion, fuzz, compressors .

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 being hooked up opposite, anything that both coils in the pickup receive the same amount ends up being subtracted.

So why doesn't that happen to the strings as well? That's where the other part comes in: due to one coil having the magnets flipped, the signal from these coils are idential but one of them is flipped - and subtracting a wave from it's flipped form works out as addition again.

And yeah, that 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's pretty decent for lower frequencies, and sources that are further away. Mains hum is both of those, so it works 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 each.

Individual pole or rail

Passive or active?

Coil tap or split coil?

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.