Record players and phonographs
by Chris Woodford. Last updated: July 15, 2014.
If you're under the age of 20 or so, you probably get most—if not all—your music online. You might have a few compact discs lying around but they're
pretty old hat now, right? Your parents might not think so. To them,
CDs are probably still relatively new technology and, depending on
how serious they are about music, they may have quite a lot of
recordings in older forms, such as long-playing (LP) records. The
machines that play records, record players (also known as turntables and, historically,
as phonographs and gramophones), are still widely used by club DJs and music aficionados who swear the music they make is finer and more subtle. Whether or not that's true, record players can certainly teach us some interesting
things about how sound works. Let's take a closer look!
Photo: This old-fashioned "gramophone" record player from the early 20th century was the iPod of its day. Music was stored on plastic discs roughly 30cm (12 inches) across.
How modern gadgets store musical sounds
Modern music players are essentially specialized computers that store sound as
just another kind of information: they can store text files, videos, and photos
in much the same way. If you have an MP3 player, such as an iPod, it
stores your music on an internal hard-drive or
flash memory (similar to the memories in
USB sticks and digital camera memory cards). The music is stored in a
(numeric) format, with all the individual sound frequencies converted
into long strings of numbers and compressed mathematically so it
takes up very little space (which means you can download it quickly).
Hard drives read and record information using magnetism: a moving
electromagnet-arm reads and writes tiny magnetic zones by sweeping
back and forth across a rapidly spinning disc. Flash-memory
music players are slightly different: they record the digits that represent musical sounds using tiny
electronic switches known as transistors. Compact discs store music
digitally as well, but the numbers are "pressed" into the shiny
surface of the disc in the form of microscopic bumps (called pits)
that a CD player reads using a laser beam. The great thing about all
these forms of computer memory is that they retain the information they store even when
the power is switched off.
Okay, so far so good. Now imagine you're Thomas Edison back in the 19th century. You
want to record and play back sounds but you have no fancy electrical
or magnetic gadgets at your disposal. Remember this is long before
computers, laser beams, and compact discs have been invented... and it's
even before homes have electric power! The modern conveniences we
take for granted may not have been discovered in Edison's era, but there was plenty
of ingenuity around—and that's what Edison used to such stunning
effect. Here's how he solved the problem of storing and playing back
Photo: How do you make an alien die of laughter? In the mid-1970s, when LP records were still considered the height of musical technology, the Voyager spacecraft blasted into space carrying gold-colored LP records containing various sound recordings of life on Earth, including greetings in 60 Earth languages and various snippets of music. Why did we think this was a good idea? If alien life forms had already evolved beyond crude mechanical sound recordings, as we have now done on Earth, presumably they'd have found our LPs utterly primitive as they struggled to play them on their intergalactic iPods? And if not, would they even have been able to play them at all? Photo by NASA Jet Propulsion Laboratory courtesy of Great Images in NASA.
How can you store sound without magnetism or electricity?
When you were younger, you probably did something all children like to do: whenever
you walked past iron railings, you ran your fingers down them to make
musical sounds. If you're were lucky enough to live in a street where
lots of people had different kinds of railings, you might have
discovered you could get different musical notes as you moved from
house to house. Where does the sound come from? When you move your
hands and arms, you give them some kinetic energy (the energy that
moving objects have). Strike your hands against metal railings and
you transfer some energy to the the railings. The railings, which are
probably hollow iron bars, vibrate like metal organ pipes and produce
musical notes that depend on their length (longer railings produce
deeper notes, of lower pitch, than shorter ones). All traditional
musical instruments work by vibrating in some way. When they vibrate,
they make the air around them vibrate too. This carries energy to our
ears, where our eardrums vibrate in sympathy—and our brains decode
those vibrations to give us the sensation of sound.
Photo: From drums and cymbals to pianos and violins, musical sound comes from things that vibrate.
One way to record sound is to store vibrations—which is exactly how record players work. Photo by William R. Goodwin
courtesy of US Navy.
How to store sound mechanically
Now suppose you want to play a tune. If you know your street well, and you can run
really fast, you could (in theory) dart back and forth picking out
each note on a different bit of railing on a different house. Let's
say you do this a few times until you can remember the tune exactly.
Now you decide you're tired of all this scurrying back and forth so,
with the kind cooperation of your neighbors, you saw out all the
railing bars you've played and mount them, in line, in order, in a
special wooden stand in the middle of the street. All you have to do
to play your tune now is run your hand down the railings and the tune
will be magically recreated. Anyone else will be able to play the
tune too (it doesn't take a musician to run a hand down some
railings). But the big drawback is that the "musical instrument"
you've created can only ever play one tune. No matter. If you feel
like listening to a different tune, you can just move to a different
street and repeat the same trick with a different set of railings!
This way of storing sound in a "physical form" and playing it
back with vibrations was the big idea behind Thomas Edison's
sound-recording machine or phonograph. He didn't use metal
railings, of course, but the basic science was essentially the same: he stored sounds
by making bumps in a metal surface and he turned the bumps back into sound by
running a mechanical "finger" along them.
How Edison's phonograph worked
Photo: An early Edison phonograph. This one is an exhibit at
Think Tank, the science museum in Birmingham, England.
Edison called his sound-recording machine the phonograph, which
means literally "sound-writer." It had a wooden cylinder with a thin
sheet of foil wrapped round it, and a sturdy needle with a horn attached
to it pressed against the foil. Edison spoke into the horn and the
sound energy from his voice, funneled and concentrated by the horn,
made the needle vibrate up and down. As Edison cranked a handle, the
cylinder rotated and the needle cut a groove into the foil. Since the
needle was moving up and down, the depth of the groove varied
according to how loud or soft his voice was; in other words, the
groove was a recording of the sound of Edison's voice translated into
a mechanical form.
To play back the recorded sound, Edison simply ran the process in reverse. He put the
needle back at the start of the groove and cranked the handle.
Obediently, the needle ran along the groove, jolting up and down to
follow the pattern it had cut previously. As it moved about, it
vibrated and the noise of its vibrations was amplified by the horn,
recreating the sound of Edison's voice—albeit in a very scratchy-
Artwork: Edison's iPod! How did the phonograph work? If you want to record sound, you speak into the tube (1). The sound energy from your voice makes a diaphragm (like a mini drumskin) vibrate, pushing a needle (2) back and forth and cutting a groove into some metal foil wrapped around a cylinder (3), which is slowly turned by a clockwork (wind-up) motor.
Playback runs this process in reverse. Another needle (4) presses into the groove, bouncing up and down in the pattern previously cut there.
Another diaphragm and horn (5) amplify the sounds and turn them back into sounds you can hear. Artwork courtesy of
US Patent and Trademark Office (coloring and numbering added).
Edison developed his original phonograph in the 1870s. About a decade later, he
improved the idea, replacing the metallic foil with wax cylinders, each of which could store several minutes of recorded sound. In the early
years of the 20th century, thanks to other pioneers such as Emile Berliner, wax cylinders were themselves replaced by flat discs
and the phonograph evolved into the record player—an affordable
invention that enabled people in every home to listen to pre-recorded
music, whether or not they could play instruments themselves. In the
19th century, people who wanted to hear music had to listen to
musicians playing live; in the 20th century, most people listened to
prerecorded music. Edison's phonograph, and all the inventions that
built-on it, were responsible for this enormous social change.
Find out more
Photo: Good enough to replace a concert orchestra? This early advertisement for Edison's phonograph may have been stretching the truth just a little: the sound was scratchy and appalling! But as
a long-term prediction, this ad was bang on the money: a little over a century later, far more people listen to
recorded music than live concerts. Image believed to be in the public domain courtesy of
US Library of Congress.
How record players work
Record players were in widespread use until the late 1980s and early 1990s, when the
popularity of CD players rapidly made them obsolete for pretty much
everyone except professional DJs.
A modern record player or turntable works in almost exactly the same way as Edison's
phonograph, but with one major difference. The Edison machine relied
on a large horn to amplify sound waves during playback, so it was
entirely mechanical. Modern record players use electromagnetic
devices to convert sound vibrations from a spinning record into
electrical signals, which are then fed to an electronic amplifier
that powers loudspeakers or
headphones, making the sound much louder.
So a modern record player is a mixture of mechanical and
Photo: This beautifully preserved phonograph from the 1920s played
records at a speed of 78 revolutions per minute (rpm). Left: Note the wind-up crank on the right of the case (this model predated electric-powered phonographs) and the amazing pleated diaphragm loudspeaker: (I think it's a Sterling Primax—any audiophiles out there please do email and correct me if I'm wrong). Right: A closeup of the very sharp needle tracking its way through the record groove.
A typical record player has a stylus (similar to the needle in Edison's machine) that
bumps up and down in the groove of a vinyl (plastic) disc. The stylus
is a tiny crystal of sapphire or diamond mounted at the very end of a
lightweight metal bar. As the crystal vibrates in the groove, its
microscopic bounces are transmitted down the bar. The stylus fits onto the end of an
electromagnetic device called a cartridge, containing a
The metal bar presses against the crystal and, each time it moves, it wobbles the crystal slightly, generating an electrical signal. These signals are fed out to the amplifier to make the sounds
you hear through your speakers or phones. Not all record-player
cartridges use piezoelectricity to convert sound vibrations to
electric signals. Some have tiny electrical coils and a magnet inside
them. When the stylus moves, it pushes the magnet up and down past
the coil, generating electrical signals that way.
Photo: Left: A modern LP record stylus, mounted in a yellow protective plastic case, seen from underneath. The case snaps onto a magnetic cartridge, enabling the stylus to transmit vibrations from the record surface. Look closely at the stylus and you can see the silver-colored metal bar that does the important work. The bump at the end of it is a tiny piece of industrial diamond that bounces up and down the record groove. This tiny bump is all that tracks through the groove in the record, so you can get some idea how big that groove is.
Modern record players play two sizes of disc. LP (long-playing records) are about
30cm (12in) in diameter and roughly the same thickness as a CD.
They spin around at a speed of 33rpm (revolutions per minute), and it takes about 20–30 minutes for the stylus
to move from the outside edge of the disc to the very center, so
that's how much music a disc like this can store. Unlike a compact
disc, both sides of the disc can store sound so an LP's total playing
time is typically 40–60 minutes (you have to turn the disc over
manually to play the second side). Record players can also play smaller
discs roughly 18cm (7in) across, but at the higher speed of 45rpm.
Spinning almost half as fast again as LPs, 45s play a single track of
music lasting typically about 3–5 minutes. As with LP records, 45s
play on both sides.
The parts of a turntable
Turntables themselves are relatively simple machines: little more than spinning
wheels powered by
electric motors. The motor either turns the
turntable directly using gears (known as direct drive) or
using a thin rubber belt looped over the motor and the central axle
of the turntable (known as belt drive). Powering the turntable
at exactly the right speed is absolutely critical for playing the
music correctly. If the turntable spins too slowly, the music slows
down too and women singers end up sounding like men! Some turntables
have little reflective studs around the edge and built-in
strobe lights. You adjust the speed of the turntable with a screw, and when
it's spinning at just the right speed the flickering strobe light
makes the studs appear completely motionless.
This photo shows very nicely how a record player works. Turn on the machine and an electric motor (not shown) makes the black vinyl disc rotate around the silver peg in the center. You lower the tonearm (a pivoted lever with the stylus and cartridge on the end) onto the outer edge of the disk and wait for the little diamond tip to fall into the groove with an amplified clunking sound. The stylus then slowly "reads" the music written on the disk as the little diamond crystal at its tip (a tiny dot beneath the red plastic guard at the front) drags through the groove. The stylus feeds vibrations to the piezoelectric cartridge (gray plastic), which passes electrical signals through the gold-colored terminals at the back. Cables run from these terminals through the tonearm to an output socket somewhere on the record player's outer case,
which you hook up to your amplifier and speakers.
Photo: An LP record player making music the old-fashioned way. This wonderfully
atmospheric photo is by Orin Zebest, kindly published
on Flickr in 2008
under a Creative Commons
Analog and digital
In short, you can see that a record player is a little bit like a CD player (it plays flat discs on which
music is stored by tracking an arm across them). But the way it reads the music and the way that music
is stored on the disc are totally different:
- A record player is an analog device: the music is stored as bumps on the disc, with the size of the bumps directly corresponding to the musical notes they store. Introduce some extra bumps (by scratching your vinyl record) and you'll find some added "music" when you play back the disk—scratchy and crackly noises you really don't want to hear.
- A CD player is a digital device: the music is stored on a CD in the form of numbers, represented by little bumps that are read by a laser. In theory, the disc can be dirty or damaged and it won't make any difference to the quality of the sound you hear. In practice, a really dirty or damaged disc often won't play at all (something that seldom happened with vinyl records, which you could always play one way or another).
Are CDs better than records? Do they sound better? Do they last longer? All these things are moot points about which audiophiles still argue. Generally, people now buy music as downloads or CDs because that's the only form it comes in. The world didn't switch to digital music because it was superior technology but because music publishing companies flooded the shops with CDs and gradually stopped making LPs. We had no choice!
On this website
- US Patent 200,521: Improvement in phonograph or speaking machines by Thomas Edison. February 19, 1878. The full description of Edison's phonograph in his own words.
- US Patent 372,786: Gramophone by Emile Berliner. November 8, 1887. Emile Berliner invented the disc-type of gramophone. Here's one of his earliest patents for a sound-recording and playback gramophone clearly evolved from Edison's phonograph.
- US Patent 917,790: Gramophone by Henry F. Peltier. April 13, 1909. in this slightly later patent, you can see how the phonograph is slowly turning into its more modern incarnation, with an arm that sweeps across the surface of a flat disc and a large playback horn.
- US Patent 3,619,449: Methods of manufacturing gramophone records by Daniel Berard, Les Industries Musicales et Electriques Pathe Marconi, Paris. November 9, 1971. How are plastic LP records made? This patent describes the process in detail, from the way the plastic is molded to how the grooves are pressed.