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, impact (they are common in electronic drumkits), and in theory bending.

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. But they are not the only or often even best way to do that.)

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

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

In the case of a guitar, the vibrations of the string becomes the signal on the coil, pretty directly.

This is why such guitar pickups only work with metal strings, and do not pick up anything acoustic at all so the rest of the guitar's design barely matters to the sound.

Single coil or humbucker

Coils are by nature an antenna, so are 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 worse by certain effects, including distortion, fuzz, compressors .

The simplest pickup is a single-coil pickup, which don't address this at all.

People then thought up humbuckers, a setup that takes

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

You can work this out on paper if you want, but practically, due to being hooked up opposite, anything that both parts of the pickup pick up the same amount ends up being subtracted from that other near-copy.

It's far from perfect, not least because of the varying position, but it's pretty decent for things that further away and low frequency - and mains hum is that.

The movement from the nearby string, on the other end, will end up being picked up opposite (due to the flipped magnetics in the pickup) so that subtraction ends up being addition again.

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

Single coils tend to be brighter (and used in surf, guitar, sixties sounds), humbuckers tend to be bassier.

And then there are distinct designs of each.

Individual pole or rail

Passive or active?

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 a groove to rest on one string (that you're not playing) to help align and pivot is to modulate the effect, the other to indicate where it 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.