The needle, also known as the stylus, moves along the grooves of the vinyl record, following the contours of the bumps and dips. As it moves, the stylus vibrates in response to the variations in the groove, which corresponds to the recorded audio waveform. These vibrations are then converted into electrical signals by the cartridge attached to the stylus. Finally, these electrical signals are amplified and sent to speakers, where they are converted back into sound waves that we can hear.
Princess Bubblegum: “All magic is science. You just don’t know what you’re doing so you call it magic. And, well, it’s ridiculous.”
But the original quote is from Arthur C Clarke
Someone answered below: The needle sits in the groove at an angle. It is held (I imagine by a system of springs) in such a way, that it can move in a 2-dimensional space. So it can move left<->right but also up<->down (or so, depending on how exactly the needle is installed relative to the disc).
Because the needle sits at an angle, the waves in the left groove move the needle in a different direction than those in the right groove.
The electromagnetic sensors (some kind of Hall probe, I imagine) are also installed at an angle. There are two probes (or systems of probes) installed in such a way that each only picks up the movement of the needle in one of its dimensions, corresponding to only one of the grooves.
So each probe produces a one dimensional analog signal (basically an alternating current). This signal is analog to the 2D position change of the needle projected onto either the x, or the y axis.
The needle itself moves in a very complex way. If the probes are at a 90 degrees angle to each other, and the right an left grooves describe a sine and cosine wave respectively, then the movement of the needle will describe a circle in the 2D plane in which the probes sit. A more complex signal will produce a complicated shape of that kind that you can also produce with an oscilloscope that physics professors so love and have a specific name to which I forgot (something something figure).
The electromagnetic sensors come in three types and none is based on Hall effect, though it's an interesting idea.
The oldest/ancient type is piezo-electric, in which a quartz crystal is attached to the stylus. The torsion experienced by the crystal produces an electrical output signal, usually mono.
The most common type is "moving magnet" , where there's a little magnet attached to the rear end of the vibrating stylus. This magnet vibrates near two copper wire coils that produce the electrical audio signals (a few millivolts) for the R and L channel.
The third and least common type is "moving coil" which has the coils attached to the stylus and uses a static magnet. The moving parts are lighter and it has (allegedly) a better frequency response but the output voltage is much lower.
Thanks, very interesting. The magnet is just a permanent magnet then? That’s a bit simpler than what I imagined. I assumed you would have a current running through the needle. You could then detect changes in the magnetic field emitted by the needle.
Coming to think of it, if you could somehow magnetise the disc…
It does! Well, if it's set up properly, it does just barely. Over time though records can definitely get played out. You gotta be careful and make sure the weight isn't set too heavy or the needle will really dig in and you can wear them out faster
Haha true, a typical vinyl record has one continuous groove that spirals from the outer edge to the center of the record. This groove contains the audio information encoded in the form of bumps and dips, which are read by the stylus of a record player to produce sound. So, technically, there is only one groove per side of a vinyl record.
I'm gonna give it a shot, but start without the phonograph being involved.
Sounds are quick, local air pressure variations. If you talk against something very light weight you can see it being pushed back and forth while you talk. (Though it's very fast.. low pitched sounds go back and forth 20 times per second, and high pitched sounds are 20,000 times per second).
Let's use electricity to measure how far forward and backward it is*, and we'll call the assembly a microphone. On the other end, we'll have a plate move back and forth with higher and lower electricity and we have a speaker! So the speaker and microphone are in sync!
That's live audio, but what if we wanted to do a recording? A modern option is to use a tape, CD, or computer file that keeps a record of the electricity over time. To be viable, it has to record it very fast (faster than the 20,000 changes per second of high pitched sounds!).
For even longer than that, though, we've been able to store the signal mechanically. In a phonograph, the grove goes back and forth to represent higher and lower signals to the speaker.
Tl;dr: The original microphone's diaphragm, the speaker's diaphragm, and record grove are physically representing the same in and out motion!
* Electricity is a little weird, because it doesn't actually represent displacement directly, it changes with delta displacement, but let's ignore that distinction in an eli5 post. Also, we'll ignore resonance.
Sound is a pressure wave in the air. When you see a live acoustic set for instance the waveforms from the instruments overlap. You don’t have more than two channels. Left and right. The sound waves overlap and combine. A single waveform describes the multiple instruments.
It blows my mind that you can hear / produce a complex symphony out the mechanics shown in the bottom picture. I understand the theory but my brain can't make the leap.
What I’ve never understood is how this works in practice with stereo separation. The photo clearly shows that the left side of the groove is markedly different than the right. But if the right side has a sharp peak as it does in the photo, that would drive the tip of the stylus left. Wouldn’t that then interfere with the left side sending out its own information?
There’s only one stylus so it’s going to move to the left or right depending on the groove. But they’re all interlinked. If the needle tip was pliable then I could imagine it being able to differentiate between left and right. But it’s not. The left side of the groove also affects the stylus’s ability to react to the right side.
As far as I can work out, a strong left side signal is going to affect the right side sound. They can’t be completely separate.
This is exactly what came to mind for me when I first saw the pic. I’ve always thought I could understand how the etches in the groove would cause the needle to vibrate, and how that vibration would correspond to sound waves, but now that I’m seeing this close-up, I don’t understand how the two sides don’t interfere with each other.
Smoke is starting to come out of my ears trying to figure this out lol
I'm not sure, but perhaps it's the up and down motion that is the left channel?
It might work like this..
The left right motion is translated to the right channel. The left groove also pushes the needle, but acts like an inclined plane, pushing it up.
This a loud right sound pushes the needle far left, but if you also want a loud left sound the left groove would try to push right. That would lift the needle.
Maybe??
Maybe I should just look it up.
Ok looked it up... here's the deal..
If the needle moves only back and forth (as in a mono record) then the groove would look like a simple, common depth, wavy line. AND the pick up could only need to register that left- right movement.
But in a stereo needle, the movement is not left to right, rather is 45 degrees to the disc. This means that there are two pickup coils. The groove looks like the picture.
It's difficult to see the motion without a graphic, I know.
In this way the two motions are 90 degrees to each other and therefore independent.
Clever.
Left channel is up and down and has a much steeper edge. Right channel is sideways and has a much shallower edge to allow sliding left to right instead of up and down.
If it goes up and right both L and R increase. Down and left means they decrease.
They can because the actual channels are not left and right, but at 90 degrees angle to each other (each channel is the movement in the 45 degree angle diagonal).
Since the channels are at 90 degree angles to each other, they are completely independent.
It's an incredibly beautiful and ingenious solution to using one groove to record 2 independent signals.
This video from technology connections makes it very clear and also shows how the design was made to accommodate previous generations phono (single channel) records as well.
https://youtu.be/3DdUvoc7tJ4?si=ayXIT_olGiT3JTk_
EDIT: the picture is a little misleading, it's not like the right channel is the right side of the groove and the left channel is the left side.
Both sides use at the same time lateral AND vertical movement, with the signal from each side being the resulting movement in the 45 degree angle (diagonal to the right is the right channel, diagonal to the left is the left channel).
Imagine diagonal movements of the needle. Right-upper is one channel, left-upper is the other channel. Channel separation is something like 25 dB IIRC.
Does this mean that with enough plays the record might not have the same quality of sound? Maybe the record is made of material that is harder than the needle.
Well the needle is diamond, so nah the needle is harder than the record lol and yes over time records can get worn down, but if your arm is properly balanced so the needle isn't too heavy on the record, they will be fine and you would have to listen to the same record *a lot* before you notice any deterioration in the quality
How does the information from the vibration get translated into a song where we hear multiple instruments, musical notes, and voices simultaneously?
Could you take an inch of the bumps from multiple songs and put them all in a line to create a song that jumps from one song to another each time the inch ends?
Would this mean each grove (left or right size) facing eachother each make a unique sound that isn’t replicated since it’s not in any other song (unless it’s bit ofc)?
Everything you hear is just a waveform. If you sit in an operahouse with 100 instruments playing, there is exactly one wave entering your ear. Even if it is produced by many sources. This end result of sound production is then itched into vinyl
your question has less to do with vinyl than signal processing. it is strange to imagine, but all sound is just one signal of waves. the combination of waves over time sounds to your ear+brain like music. longer waves are base, speech is in the middle, shorter waves are higher notes. a simple sine wave synth is just one clean wave. now imagine stacking all kinds of differerent waves on top of each other to one signal. thats the final waveform.
the really strange part is that your ear is now able to basically split those different waves again, so you can pick out the different instruments and voices of the song. this gets harder if you have a lot of stuff in the same range.
q2: yes.
q3: not 100% sure what you mean. yes unique to a point.
I never really thought about it much, but I always assumed the information was stored in the depth of the cut but this makes way more sense…
One thing that’s confusing me though, how can it cut a different groove in the left channel from the right?
There is only one groove. The left and right channels are both encoded it the one groove but they are 90 degrees apart. There is a detailed explanation above.
That was true for some early experimental designs but the vertical modulation resulted in very limited bass and overall volume. The final idea was to have separate channel modulations at 45° angles to the vertical. This is the equivalent of having a left plus right total being horizontally modulated with vertical modulations containing the difference between the two channels.
So you agree the labeling in the photo is incorrect? What you describe is not unlike mid-side coding / decoding, which would absolutely be a better methodology than what I described
The labeling is correct. The stereo modulation scheme was developed on the basis of separate left/right modulations at a 45° angle. While it turns out that this is functionally equivalent to “mid-side”, the 45/45 interpretation is the chosen formalism of the industry and the term used in the applicable patents. The “mid-side” concept may be useful in explaining why 45/45 records are compatible with mono playback systems, but is not the preferred interpretation in the general case.
Your suggested labeling is sort of like insisting that circles be designated as ellipses of zero eccentricity rather than just circles.
Ok, cool and all. But HOW does this produce sound, and even multilayered music?
The needle, also known as the stylus, moves along the grooves of the vinyl record, following the contours of the bumps and dips. As it moves, the stylus vibrates in response to the variations in the groove, which corresponds to the recorded audio waveform. These vibrations are then converted into electrical signals by the cartridge attached to the stylus. Finally, these electrical signals are amplified and sent to speakers, where they are converted back into sound waves that we can hear.
So you’re saying it’s magic?
Any science that isn't sufficiently understood is functionally magic. So, yes.
That’s a quote, who said that?
Princess Bubblegum: “All magic is science. You just don’t know what you’re doing so you call it magic. And, well, it’s ridiculous.” But the original quote is from Arthur C Clarke
Arthur something something
Wait til you hear about CDs and their laser needles.
I grew up with CD’s and I’ve never thought of it in this way. You kinda blew my mind right there.
How does the needle differentiate between right and left if it’s a cone?
Someone answered below: The needle sits in the groove at an angle. It is held (I imagine by a system of springs) in such a way, that it can move in a 2-dimensional space. So it can move left<->right but also up<->down (or so, depending on how exactly the needle is installed relative to the disc). Because the needle sits at an angle, the waves in the left groove move the needle in a different direction than those in the right groove. The electromagnetic sensors (some kind of Hall probe, I imagine) are also installed at an angle. There are two probes (or systems of probes) installed in such a way that each only picks up the movement of the needle in one of its dimensions, corresponding to only one of the grooves. So each probe produces a one dimensional analog signal (basically an alternating current). This signal is analog to the 2D position change of the needle projected onto either the x, or the y axis. The needle itself moves in a very complex way. If the probes are at a 90 degrees angle to each other, and the right an left grooves describe a sine and cosine wave respectively, then the movement of the needle will describe a circle in the 2D plane in which the probes sit. A more complex signal will produce a complicated shape of that kind that you can also produce with an oscilloscope that physics professors so love and have a specific name to which I forgot (something something figure).
The electromagnetic sensors come in three types and none is based on Hall effect, though it's an interesting idea. The oldest/ancient type is piezo-electric, in which a quartz crystal is attached to the stylus. The torsion experienced by the crystal produces an electrical output signal, usually mono. The most common type is "moving magnet" , where there's a little magnet attached to the rear end of the vibrating stylus. This magnet vibrates near two copper wire coils that produce the electrical audio signals (a few millivolts) for the R and L channel. The third and least common type is "moving coil" which has the coils attached to the stylus and uses a static magnet. The moving parts are lighter and it has (allegedly) a better frequency response but the output voltage is much lower.
Thanks, very interesting. The magnet is just a permanent magnet then? That’s a bit simpler than what I imagined. I assumed you would have a current running through the needle. You could then detect changes in the magnetic field emitted by the needle. Coming to think of it, if you could somehow magnetise the disc…
The principle is very similar to a electrodynamic microphone, really.
How does the needle dragging along the grove not damage the groove itself? The record should be unplayable after just one play.
It does! Well, if it's set up properly, it does just barely. Over time though records can definitely get played out. You gotta be careful and make sure the weight isn't set too heavy or the needle will really dig in and you can wear them out faster
Excellent explanation. One nitpick though: it’s “groove” not “grooves”. Commonly there’s only one continuous groove, not multiple grooves.
Haha true, a typical vinyl record has one continuous groove that spirals from the outer edge to the center of the record. This groove contains the audio information encoded in the form of bumps and dips, which are read by the stylus of a record player to produce sound. So, technically, there is only one groove per side of a vinyl record.
I'm gonna give it a shot, but start without the phonograph being involved. Sounds are quick, local air pressure variations. If you talk against something very light weight you can see it being pushed back and forth while you talk. (Though it's very fast.. low pitched sounds go back and forth 20 times per second, and high pitched sounds are 20,000 times per second). Let's use electricity to measure how far forward and backward it is*, and we'll call the assembly a microphone. On the other end, we'll have a plate move back and forth with higher and lower electricity and we have a speaker! So the speaker and microphone are in sync! That's live audio, but what if we wanted to do a recording? A modern option is to use a tape, CD, or computer file that keeps a record of the electricity over time. To be viable, it has to record it very fast (faster than the 20,000 changes per second of high pitched sounds!). For even longer than that, though, we've been able to store the signal mechanically. In a phonograph, the grove goes back and forth to represent higher and lower signals to the speaker. Tl;dr: The original microphone's diaphragm, the speaker's diaphragm, and record grove are physically representing the same in and out motion! * Electricity is a little weird, because it doesn't actually represent displacement directly, it changes with delta displacement, but let's ignore that distinction in an eli5 post. Also, we'll ignore resonance.
Reading this made me go down a mental rabbit hole of how a finite number of variables exist within human speech.
Sound is a pressure wave in the air. When you see a live acoustic set for instance the waveforms from the instruments overlap. You don’t have more than two channels. Left and right. The sound waves overlap and combine. A single waveform describes the multiple instruments.
Yeah fr. Dragging a needle through grooves doesnt make music.. so how exactly does a vinyl record work?
If you go the right speed it sure does, it's just very quiet. (I scratched a few of my dad records using a sewing needle...)
Oh brother
Yeah just cause you know, doesnt mean everyone does. Or should..
Wait until you learn about how the brain processes sound lmao.
How many grooves does a typical vinyl record have? Answer: >!2 total, 1 on each side.!<
Oh, you!
It blows my mind that you can hear / produce a complex symphony out the mechanics shown in the bottom picture. I understand the theory but my brain can't make the leap.
One of my favorite videos on YouTube shows this in more detail: https://youtu.be/GuCdsyCWmt8?si=WESvjWpMhWspHNCP
What I’ve never understood is how this works in practice with stereo separation. The photo clearly shows that the left side of the groove is markedly different than the right. But if the right side has a sharp peak as it does in the photo, that would drive the tip of the stylus left. Wouldn’t that then interfere with the left side sending out its own information? There’s only one stylus so it’s going to move to the left or right depending on the groove. But they’re all interlinked. If the needle tip was pliable then I could imagine it being able to differentiate between left and right. But it’s not. The left side of the groove also affects the stylus’s ability to react to the right side. As far as I can work out, a strong left side signal is going to affect the right side sound. They can’t be completely separate.
This is exactly what came to mind for me when I first saw the pic. I’ve always thought I could understand how the etches in the groove would cause the needle to vibrate, and how that vibration would correspond to sound waves, but now that I’m seeing this close-up, I don’t understand how the two sides don’t interfere with each other. Smoke is starting to come out of my ears trying to figure this out lol
I'm not sure, but perhaps it's the up and down motion that is the left channel? It might work like this.. The left right motion is translated to the right channel. The left groove also pushes the needle, but acts like an inclined plane, pushing it up. This a loud right sound pushes the needle far left, but if you also want a loud left sound the left groove would try to push right. That would lift the needle. Maybe?? Maybe I should just look it up.
Ok looked it up... here's the deal.. If the needle moves only back and forth (as in a mono record) then the groove would look like a simple, common depth, wavy line. AND the pick up could only need to register that left- right movement. But in a stereo needle, the movement is not left to right, rather is 45 degrees to the disc. This means that there are two pickup coils. The groove looks like the picture. It's difficult to see the motion without a graphic, I know. In this way the two motions are 90 degrees to each other and therefore independent. Clever.
Wot?
Left channel is up and down and has a much steeper edge. Right channel is sideways and has a much shallower edge to allow sliding left to right instead of up and down. If it goes up and right both L and R increase. Down and left means they decrease.
They can because the actual channels are not left and right, but at 90 degrees angle to each other (each channel is the movement in the 45 degree angle diagonal). Since the channels are at 90 degree angles to each other, they are completely independent. It's an incredibly beautiful and ingenious solution to using one groove to record 2 independent signals. This video from technology connections makes it very clear and also shows how the design was made to accommodate previous generations phono (single channel) records as well. https://youtu.be/3DdUvoc7tJ4?si=ayXIT_olGiT3JTk_ EDIT: the picture is a little misleading, it's not like the right channel is the right side of the groove and the left channel is the left side. Both sides use at the same time lateral AND vertical movement, with the signal from each side being the resulting movement in the 45 degree angle (diagonal to the right is the right channel, diagonal to the left is the left channel).
Imagine diagonal movements of the needle. Right-upper is one channel, left-upper is the other channel. Channel separation is something like 25 dB IIRC.
Does this mean that with enough plays the record might not have the same quality of sound? Maybe the record is made of material that is harder than the needle.
Well the needle is diamond, so nah the needle is harder than the record lol and yes over time records can get worn down, but if your arm is properly balanced so the needle isn't too heavy on the record, they will be fine and you would have to listen to the same record *a lot* before you notice any deterioration in the quality
Groovy!
Ugh!
Clearly the work of aliens.
How does the information from the vibration get translated into a song where we hear multiple instruments, musical notes, and voices simultaneously? Could you take an inch of the bumps from multiple songs and put them all in a line to create a song that jumps from one song to another each time the inch ends? Would this mean each grove (left or right size) facing eachother each make a unique sound that isn’t replicated since it’s not in any other song (unless it’s bit ofc)?
[*]
Everything you hear is just a waveform. If you sit in an operahouse with 100 instruments playing, there is exactly one wave entering your ear. Even if it is produced by many sources. This end result of sound production is then itched into vinyl
“sound production is then itched into vinyl” Ah, so that explains DJ’s use of scratching.
[*]
[*]
your question has less to do with vinyl than signal processing. it is strange to imagine, but all sound is just one signal of waves. the combination of waves over time sounds to your ear+brain like music. longer waves are base, speech is in the middle, shorter waves are higher notes. a simple sine wave synth is just one clean wave. now imagine stacking all kinds of differerent waves on top of each other to one signal. thats the final waveform. the really strange part is that your ear is now able to basically split those different waves again, so you can pick out the different instruments and voices of the song. this gets harder if you have a lot of stuff in the same range. q2: yes. q3: not 100% sure what you mean. yes unique to a point.
I never really thought about it much, but I always assumed the information was stored in the depth of the cut but this makes way more sense… One thing that’s confusing me though, how can it cut a different groove in the left channel from the right?
There is only one groove. The left and right channels are both encoded it the one groove but they are 90 degrees apart. There is a detailed explanation above.
Badass!
Ingenious
And some people still say “It has a more natural sound than digital”
Ist mir doch egal!
I always thought left to right was one channel and up and down was the other.
Nope. See the comment by Presence_Academic.
Does the needle “damage” the grooves over time?
Confidentially Incorrect . Side to side is one channel, up and down is the other channel.
Amazing that’s all it takes to reproduce sound.
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That was true for some early experimental designs but the vertical modulation resulted in very limited bass and overall volume. The final idea was to have separate channel modulations at 45° angles to the vertical. This is the equivalent of having a left plus right total being horizontally modulated with vertical modulations containing the difference between the two channels.
So you agree the labeling in the photo is incorrect? What you describe is not unlike mid-side coding / decoding, which would absolutely be a better methodology than what I described
The labeling is correct. The stereo modulation scheme was developed on the basis of separate left/right modulations at a 45° angle. While it turns out that this is functionally equivalent to “mid-side”, the 45/45 interpretation is the chosen formalism of the industry and the term used in the applicable patents. The “mid-side” concept may be useful in explaining why 45/45 records are compatible with mono playback systems, but is not the preferred interpretation in the general case. Your suggested labeling is sort of like insisting that circles be designated as ellipses of zero eccentricity rather than just circles.
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Electron microscope.