Electronic music - pickups: Difference between revisions
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When you move a magnet near a wire, current flows. | For context: When you move a magnet near a wire, current flows. | ||
This is how an | This is e.g. how an [https://en.wikipedia.org/wiki/Electric_generator electric generator] works, turning movement into electricity. | ||
A guitar does something similar, but instead of moving the magnet, it moves the wire | A guitar does something similar, but instead of moving the magnet near a wire, it moves the wire near a magnet. | ||
It's not that the strings are magnetic, it's that the pickup has two distinct parts: magnets, and a coil. | It's not that the strings are magnetic (that would work, but be hard to make), | ||
The magnet is there to set up a field strong enough for the coils to then notice the variation in | it's that that is done by the pickup as well. | ||
The pickup has two distinct parts: magnets, and a coil. | |||
The magnet is there only to set up a field strong enough for the coils to then notice the variation in. | |||
A variation caused by the movement of a conductor - the strings. | |||
The vibrations of the string becomes the signal on the coil, ''fairly'' directly. | |||
This is why such guitar pickups only work with metal strings, | |||
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 | 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 | things like | ||
: hitting the body (impacts end up soft vibration of the strings), | |||
: [https://en.wikipedia.org/wiki/Sympathetic_resonance sympathetic vibration] of strings | |||
: shaking a guitar | |||
<!-- | |||
Note that there is a difference between | |||
* vibrato while holding a string | |||
:: basically just bending | |||
* bending the neck to change the tension | |||
* shaking it in a direction that does ''not'' do the last | |||
It should be pointed out that | |||
shaking | |||
and | |||
neck bending | |||
have overlap but also un | |||
Shaking the guitar works out as [[vibrato]], because you are bending the neck slightly in a regular pattern | |||
: it's a subtler variant of using a whammy bar, useful if you don't have one. | |||
Even vertically shaking an electric guitar seems to work, | |||
so even without bending the neck it seems to also be something sympathetic with the string vibration. | |||
This works similarly on acoustic, | |||
though note not all necks are equally stiff. | |||
On acoustic you may also just get more noticeable change from just pointing the sound box elsewhere | |||
On damage | |||
Remember that there is always a good amount of tension on the neck, from the strings. | |||
Varying that slightly should not | |||
That's not to say that all bending is the same, and | |||
--> | |||
Coils are by nature an antenna. | |||
===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. | That makes them good at picking up any electromagnetism happening nearby, the strongest of which is usually the 50Hz / 60Hz power hum. | ||
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And this hum can be made more noticeable by certain audio effects, including distortion, fuzz, compressors <!--(often when they effectively reduce the dynamic range)-->. | And this hum can be made more noticeable by certain audio effects, including distortion, fuzz, compressors <!--(often when they effectively reduce the dynamic range)-->. | ||
<!-- | |||
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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And then there are distinct designs of each. | And then there are distinct designs of each. | ||
<!-- | |||
Is there merit to the "more magnet means less natural" ? | |||
--> | |||
===Individual pole or rail=== | |||
<!-- | <!-- | ||
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===Passive or active=== | |||
<!-- | <!-- | ||
Active pickups (a.k.a. hot pickups?) are any that are powered, whatever the style {{verify}} | Active pickups (a.k.a. hot pickups?) are any that are powered, whatever the style {{verify}} | ||
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===Coil tap or split coil=== | |||
<!-- | <!-- | ||
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===The circuit behind the dials=== | |||
<!-- | |||
''' | The volume dial is typically just a pot that wipes between ground on one side, and the coil output on the other. | ||
Log-scale, because that makes more sense for volume. | |||
The tone pot is more interesting. | |||
One basic construction is, basically independent of the volume dial, | |||
to have the coil output on one side of another pot, with the wiper going to ground via a capacitor, the other will be unconnected. | |||
This is a basic RC lowpass circuit, with the pot on the unconnected side introducing so much resistance that this part has no effect. | |||
With a ~200kOhm pot, a ~dozen-nF capacitor works.{{verify}} | |||
Wire to potmeter case is trying to lessen hum a little by shielding it. | |||
https://www.youtube.com/watch?v=6OcmKU5rblA | |||
--> | |||
===Multiple pickups, position, and switches=== | |||
<!-- | |||
The idea is that | |||
putting a pickup near the neck makes for a sharper tone, and | |||
putting it near the fretboard ('bridge pickup') make fir a more mellow and warm sound. | |||
[https://youtu.be/Iy9jEy6nLek?t=95 This is one of the nicest demonstrations I've found] | |||
'''Assuming you have both (or three)''' | |||
{{imagesearch|resonant string|A vibrating string physically moves more near the center of the string}}, | |||
so putting a pickup there will also be ''louder'' than putting that same pickup further away. | |||
That said, in guitars with both neck and bridge pickup, one may well be more sensitive than the other, | |||
so you can combine them with more tone than volume difference. | |||
As a side effect, the neck pickup being hotter works out as lower-noise. | |||
There is not necessarily an EQ difference {{verify}}, but | |||
The classical switch is engages one at a time, but guitarists found use in moving it to engage two at once, | |||
so on 2-pickup you may have 2-way or 3-way{{verify}}, and on 3-pickup you may have 3-way and 5-way. | |||
--> | |||
<!-- | |||
===Are you saying all electric guitars sound the same?=== | |||
Given that a magnetic pickup only picks up the string and nothing acoustic, | Given that a magnetic pickup only picks up the string and nothing acoustic, | ||
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--> | |||
===DIY pickups=== | |||
<!-- | |||
You ''can'' wind your own pickups. | You ''can'' wind your own pickups. | ||
There's a bunch of math involved, | There's a bunch of math involved, | ||
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=== | ===More on single coil hum=== | ||
<!-- | <!-- | ||
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It is. | It is. | ||
Y'all don't like the solution, though. | Y'all don't like the solution, though. | ||
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At one point there was a product called a magnetic pick. | At one point there was a product called a magnetic pick. | ||
If they called it a modulating pick it would have been fine, | If they called it a modulating pick or ducking pick it would have been fine, | ||
but because they weren't clear about it did, | but because they weren't clear about it did, | ||
and because of what the demonstration videos showed, | and because of what the demonstration videos showed, | ||
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Because it does the opposite of playing: | Because it does the opposite of playing: | ||
it effectively deafens the pickup when the magnet is close. | it effectively deafens the pickup when the magnet is close (a saturation that works out as compression?{{verify}}). | ||
That ''does'' let you add a sort of tremolo effect after you have already physically picked a string, | That ''does'' let you add a sort of tremolo effect after you have already physically picked a string, | ||
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Circuit-wise, piezos can be seen as vibration sensors in parallel with a reasonable capacitor. | Circuit-wise, piezos can be seen as vibration sensors in parallel with a reasonable capacitor. | ||
While they produce reasonable voltage, | |||
While they produce reasonable voltage, | |||
their current is low and their output impedance high, | |||
which are properties of their physical design, | |||
so largely unavoidable. | |||
This means you want a buffer, and possibly to amplify, or tame, the signal level. | This means you want a [[buffer amplifier|buffer]], and possibly to amplify, or tame, the signal level. | ||
Without such amplification, the level is not very predictable but may work for a particular case - but the capacitance will almost certainly eat the bass range (it works out as a lowpass filter). | Without such amplification, the level is not very predictable but may work for a particular case - but the capacitance will almost certainly eat the bass range (it works out as a lowpass filter). | ||
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Many circuits you'll find out there are for guitars, meaning they use a 9V battery they divide. | Many circuits you'll find out there are for guitars, meaning they use a 9V battery they divide. | ||
That circuit consists mostly of | That circuit consists mostly of | ||
* capacitor (for AC coupling | * capacitor (for [[AC coupling] and bias) | ||
* division of the power rails (to bias positive) | * division of the power rails (to bias positive) | ||
* transistor, or op amp | * transistor, or op amp | ||
Latest revision as of 23:24, 8 September 2023
Piezo elements
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
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
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, but instead of moving the magnet near a wire, it moves the wire near a magnet.
It's not that the strings are magnetic (that would work, but be hard to make), it's that that is done by the pickup as well. The pickup has two distinct parts: magnets, and a coil. The magnet is there only to set up a field strong enough for the coils to then notice the variation in.
A variation caused by the movement of a conductor - the strings.
The vibrations of the string becomes the signal on the coil, fairly directly.
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.
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
Multiple pickups, position, and switches
DIY pickups
More on single coil hum
Sustainers
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.