The very first recordings were made well over one and a half centuries ago, and the first flat, round records, very much resembling what we know and love today, appeared at the end of the nineteenth century – and the basic principle has remained unchanged ever since.
But what is that basic principle? How exactly do vinyl records and record playback work?
In this special Speakergy article, I will explain just how vinyl records work – first in a short summary and then in a more complete and detailed way, but in both cases in language and concepts that are simple and easy to follow and understand.
How Do Records Work – The Short Story
A vinyl record has a groove or a kind of valley, cut into it, which spirals around from the outside to the inside of the record in a single continuous track – while people often talk about a record’s grooves, it’s actually just one single groove. In fact, if you were able to stretch that single groove out into a straight line, it would be over 500 yards long, or close to a third of a mile!
There are modulations, which are basically bumps or notches, etched into the groove of the record, on both sides – one side for the left side of a stereo image, and the other for the right side. These modulations are the actual musical recording, and we would call them an analog representation of the music,
A turntable’s needle, which floats along on a well-balanced and frictionless tonearm, goes into this groove and traces those modulations, moving left and right, up and down with the bumps, and this moves a transducer – a physical apparatus of wires and magnets inside the record player’s cartridge which turns physical motion into electricity.
This electric music signal flows through the turntable’s wires into an amplifier, where it is amplified to a much higher level, then fed into a speaker. The speaker moves in accordance with the signal, and its movement is physically very similar to the notches on the record.
The physical movement of the speaker, or speakers, creates sound waves which are as close to possible as the sound waves coming from the original musical performance that was recorded – the voice of a singer, the sound of a piano, or the thwack of a bass drum.
The sound waves enter our ears, make our eardrums vibrate, and our brain processes the sound and recognizes it as the sound of a voice, a piano, or a drum.
Simple, right? But let’s get into a bit more detail.
Analog vs Digital Recording – What’s the Difference?
To understand how vinyl records work, it is very helpful to know what is meant by the word “analog” – remembering that newer recording technologies use digital techniques and older recordings, like records, are analog.
We can define analog, or analogue (for our British readers), as something which resembles another thing, something which is a representation of another thing, especially something which – particularly in science and engineering – is a physical representation or has a striking physical similarity to something else.
And so while digital recording uses binary code – essentially zeros and ones – to record and represent music, which code looks absolutely nothing like the music itself, analog recording uses some sort of analog representation – and in the case of vinyl records, this is a long line of physical “modulations” or bumps which look strikingly like the music itself.
More specifically, the modulations are inside the groove of a record, and they look like, and directly represent, the sound waves of the music.
When music is recorded, it is normally captured on a tape or as a digital file. Tapes are often also analog recordings – and 40 or more years ago were almost exclusively analog – and in this case, the analog representation, instead of bumps or notches in a groove, is a magnetic signal stored on that magnetic tape, which signal changes level and quality in a way very similar to the way those notches change with the changing music.
The recording is fed into a record cutting machine, which creates a master disc, a disc that is the same size and shape as the final record, but which is of even higher quality. This record-cutting machine etches a groove into this master disc, carving the modulations into the sides of that groove to make an analog of the recorded tape, which is an analog of the music – so the master disc’s modulations are also an analog of the original music.
This high-quality master disc is then used to create copies – in the case of, say, Michael Jackson or Madonna, millions and millions of copies – in a record-cutting plant, which presses exact copies of that master in a clean and dust-free environment, then packages them in paper or plastic inner sleeves and printed outer sleeves and distributes them to retailers – this last bit is, of course, greatly simplified here, but the exact details of the packaging and physical distribution of records is a bit beside our point.
Making Waves out of Waves
Now we need to understand a little more about record players or turntables and how they work.
We have an analog recording of the original music, which was recorded in a studio, at a live concert performance, in some dude’s basement, or really anywhere. This analog is a physical representation of that music in the form of modulations etched into a groove of a record.
To turn this analog recording into music, we use a record player – or, if it is a higher quality unit, more of an audiophile record player, we might get in trouble unless we call it a turntable.
A record player or turntable has a needle, or stylus, which rides inside the groove of the record. This needle is a tip, normally a finely polished industrial diamond, which protrudes from the cartridge – the little box mounted at the end of a tonearm. The tonearm, a long, slender arm that is mounted on the turntable in a way that allows it to move freely and without friction, is swung over to the record and the needle is lowered into the record’s groove.
Since the groove is in fact a single long track and is spiral when the record spins the groove will pull the tonearm and needle from the outside of the record to the inside (where the paper record label is). This happens very slowly since the record doesn’t turn that fast and the groove is, again, very long.
As the needle follows the groove, it finds and is moved by the modulations etched inside that groove. If the music is louder, or a deeper note – like the low notes of an organ, a male voice as opposed to a female voice, or a big bass drum – these modulations will be physically larger (though still quite tiny) and if the music is higher, or softer, the modulations will be relatively smaller.
In actual practice, the sound of real music as it is performed is very, very complex. Voices and instruments play together, making all kinds of different sounds at the same time, and so – as you can see in the illustrations above – sound waves and the modulations in a record groove are amazingly complex in their patterns. In fact, even a single voice or a single instrument, playing or singing a single note by itself, will create a very complex sound wave.
But the needle is very sensitive and is mounted on a very light arm sticking out of the cartridge (that tiny arm holding the needle is called a cantilever), so it can accurately track and move with even the smallest or most complex modulations in the record’s groove.
As it does, the needle moves that cantilever it is mounted on, and on the other end of the cantilever, inside the cartridge itself, is a transducer – a physical apparatus that normally consists of wires and magnets – which turns that movement into electricity – a very small and weak electrical signal which is an – you guessed it! – analog of the modulations, which are an analog of the signal on the original recording tape, which is an analog of the original musical performance.
Don’t know why, but it kind of reminds me of “I knew an old lady who swallowed a fly…”
This very small electrical signal is carried through tiny wires out of the cartridge, along the inside of the tonearm, out the back of the turntable, and to an amplifier, which then amplifies that electrical signal to power speakers.
Although I don’t want to get into the exact reason why she swallowed a fly, we can say that these electrical signals are yet another analog of the music, since they are a direct analog of the grooves in the record – that is, they move up and down in current, frequency and in other electrical qualities in a way that is electrically exactly the same as, and perfectly follows, the physical bumps and notches in the grooves.
I should mention that this electrical signal may not actually be taken “out the back of the turntable,” since with many less expensive record players the amplifier and speakers may be in the same box as that turntable – but the working principle is exactly the same.
So we have started with sound waves – the original music – and in a chain of recording and playback events – microphones, tape recorders, and tape, record cutting machines and master discs, vinyl records, turntables, styluses (or styli, if you want to sound fancy), cantilevers and cartridges, and finally an electrical signal from the cartridge’s electrical transducer – we have made several generations of analogs of that original music.
Now it’s time to turn this chain of analog representations of the original music back into, well, the original music – that is, now we make sound waves again, and amazingly, despite how many generations of analogs this music has gone through, these newly reproduced sound waves can sound exactly like the original ones.
The New Wave
So we have seen how vinyl records are used to record and hold an analog representation of music, in the form of modulations – bumps and notches cut into the groove of that record – and how a turntable reads those modulations and converts them into an electrical signal.
Now all that’s left is to turn this back into actual music, and for this, we need another transducer. Again, a transducer is something that converts physical movement into electricity – the record player’s cartridge does this and, though I didn’t mention this earlier, so does the microphone used in the original music recording session.
But a transducer can also do the opposite – that is, turn electricity into physical movement, which is just the exact same process in reverse. By using a physical apparatus of wires and magnets (there are other ways, but this is by far the most common in audio recording and reproduction) we can take an electrical signal, like the one coming from the turntable’s cartridge, and convert it into physical movement.
And, as you might have already guessed, the transducer we use for this is the speaker.
A speaker may come in the form of a box, but the real speaker is a driver – or sometimes two or more drivers – inside that box, which creates sound waves.
A speaker driver is a cone (though it can be other shapes, like a dome) that is made of high-quality paper or some other light and stable material. It has a coil of electrical wire mounted on the back, which we call a voice coil. That wire is suspended in the speaker magnet, which is also mounted on the back of the speaker driver and is usually a big and powerful round magnet.
When the electrical signal from the turntable – which, if you remember, has been amplified, or increased in current, by an amplifier – reaches that speaker driver’s voice coil, that electricity interacts with the magnetic (electrical) charge of the magnet, and this makes the cone or dome of the speaker driver move.
Now, getting back to our favorite word – analog – here’s the fascinating point. The movement of the speaker cone looks pretty much identical to the shape of the modulations in the vinyl record’s groove, or put another way the speaker moves in exactly the same way the needle did when it was reading those modulations.
When the speaker driver moves in this way, it creates air waves – again, airwaves that are essentially identical to the airwaves, or sound waves, made when the musicians originally performed, those airwaves reach your eardrums, and so your eardrums move and vibrate again in exactly the same way they would have if you were there to hear that original music performance.
I say “identical” and “exactly” kind of incorrectly here – the waves are just the same as the original sound waves, yes, and so the sound is the sound of the singer’s voice, the guitar, piano, drum, or whatever, but there will be some slight differences because your room – that is, the room where the speakers are – is different in shape, size and other conditions from the room or space where the music was originally made, as well as there being some changes along the way due to physical and electrical distortion or loss – but all of this tends to be quite minor.
That said, the airwaves, which are sound waves or music waves, again hit our ears, which send a signal to our brain, which in turn processes those sound waves as the sound of a guitar, a piano, a drum, or a human voice.
And that, my friends, is it – a series of analogs that take us from music to music, and in particular, the analog representation of that music in the form of the modulations etched into the groove of a vinyl record, and how that analog is turned back into music.
DIY Analog Playback
One quite fascinating thing about all of this is that the bumps and notches inside a vinyl record’s groove are, again, a physical analog of the original music’s sound waves – which means that those modulations look, in their way, just like the sound waves themselves.
And this means that we can do a very cool basic experiment, and convert those modulations directly into sound waves – to be more clear, what I mean is that we can make a very simple mechanical record player in just a minute or two, which doesn’t need electricity and will let you hear the music contained on the record.
And you can make this basic mechanical record player with just four items I’m sure you have lying around – a pencil, a piece of paper, a sewing needle, and some tape. Oh yeah, and a record, but really, that’s it!
Take a sheet of letter-sized or legal-sized paper and roll the paper into a cone, with the small end maybe an inch or so wide. In one or two spots, put a small piece of tape on the seam so that the cone holds together.
About a half inch from that small end, poke the needle through the paper, both sides, and push it through so that the sharp point is extended as far out as possible, but the needle is still running through both sides of the paper.
When I do this, it strikes me how much this simple apparatus looks like an old Victrola record player (and, indeed, functions in exactly the same way):
Now take a vinyl record – any record will do, but I wouldn’t recommend you do this with a nice record or one you actually play on your stereo – what we’re doing probably won’t hurt the record, but it is possible, especially if you’ve never done this before. Anyway, if you need an excuse for a trip to a thrift shop, you can probably find a gazillion records there for a quarter a piece – and some of them are absolute gems!
Put that vinyl record onto the pencil, like you were placing it on a turntable, the pencil sticking through the record’s hole. Make sure the record is pretty flat, and then spin the record – at a close to record player speed – by turning the pencil between your fingers.
Holding the paper cone/needle record player lightly on the large end, drop the needle into the groove and let it flow with that groove – this is a bit easier with two people, but one can do it.
If all is well, you will hear music!
If it is difficult to follow these verbal directions, you can also check out a video on just how to do this, like the one on the Official Mr. Wizard Site – Make a Homemade Record Player!