How A Turntable Works

A vinyl record stores sound as a tiny physical pattern in the groove. When the record spins, the stylus rides that groove, vibrates in exactly the same pattern, the cartridge turns those vibrations into a very small electrical signal, and the amplifier boosts and equalizes that signal so speakers can move air again. That is the whole chain.

Here is the full path.

1. How sound gets into the groove in the first place

Before playback, the music is cut into a master disc by a cutting lathe.

A cutting head drives a sharp cutter back and forth while the disc rotates. The cutter’s motion is controlled by the music signal:

• Side-to-side motion corresponds mainly to the mono component

• Differences between left and right channels are encoded as more complex groove wall motion

On a stereo LP, the groove is a V-shape with two groove walls set at roughly 45°/45°. One wall carries one channel’s modulation and the other wall carries the other channel’s modulation. So the stylus later reads both walls at once.

The groove is one continuous spiral from the outer edge toward the center. As the record rotates, time is represented by distance along that spiral.

Groove modulation

The groove is not varying much in depth for normal audio. The key information is in the microscopic wiggles of the groove walls:

• Low frequencies produce larger, slower groove swings

• High frequencies produce smaller, faster groove wiggles

• Loud sounds require larger groove excursions than quiet sounds

So the groove is a mechanical analog of the waveform.

2. What the stylus is physically doing

The stylus tip, usually diamond, sits in the groove under a small downward force called tracking force. As the record rotates, the groove walls push against the stylus.

The stylus does not “read” magnetically or optically in a normal turntable. It is purely mechanical contact.

Because the groove walls are modulated, the stylus is forced to move in very tiny, rapid motions. Those motions match the groove shape at each instant. In effect:

• Groove shape determines stylus position

• Changing groove shape determines stylus velocity and acceleration

• The rotating record supplies the motion past the stylus

The stylus is not moving itself through the groove under motor power. The record surface is moving under it, and the groove walls drag the stylus along.

3. Why the stylus shape matters

Different stylus profiles contact the groove differently:

• Conical: simpler, touches a smaller effective area

• Elliptical: traces high frequencies better

• Line contact / microline / Shibata: better contact with fine groove detail, lower tracing distortion

The smaller and more precise the contact geometry, the better the stylus can follow very fine, fast modulations, especially near the inner grooves where curvature is tighter and tracing is harder.

4. The cantilever: the stylus’ mechanical link

The stylus is attached to a tiny rod called the cantilever. When the stylus moves, the cantilever moves with it.

The cantilever is suspended by an elastomer or similar suspension element. This suspension has to do several jobs:

• Allow the stylus to move freely enough to follow the groove

• Keep the stylus centered

• Control resonances

• Prevent excessive motion that would cause mistracking

So the groove motion becomes cantilever motion.

This is still entirely mechanical. No electricity yet.

5. Compliance and effective mass

The stylus suspension has compliance, meaning how springy it is. The tonearm and cartridge system has effective mass. Together they form a mechanical spring-mass system.

That matters because the cartridge must:

• Be flexible enough to track modulation

• Be stable enough not to wobble at low frequencies

The tonearm-cartridge resonance usually needs to fall in a safe region, often around 8–12 Hz, below music but above most record warps. If this resonance is badly placed, tracking suffers.

6. Stereo groove motion in more detail

In stereo playback, the stylus is responding to both groove walls simultaneously.

A useful way to think about it:

• If both channels are identical, stylus motion is largely lateral

• If channels differ, there is also vertical/compound motion

More precisely, each 45° groove wall carries one channel. The cartridge’s generator system resolves the stylus/cantilever motion into two electrical outputs, left and right.

7. The cartridge: turning motion into voltage

The cartridge is a transducer. It converts the mechanical motion of the cantilever into an electrical signal.

There are two common types.

Moving Magnet (MM)

In a moving magnet cartridge:

• The stylus moves the cantilever

• A tiny magnet attached to the cantilever moves near fixed coils

• The changing magnetic field through the coils induces voltage

So the coils stay still, the magnet moves.

MM cartridges usually have:

• Higher output voltage

• Replaceable stylus assemblies more often

• Higher inductance

• More compatibility with standard phono inputs

Typical output is on the order of a few millivolts.

Moving Coil (MC)

In a moving coil cartridge:

• The cantilever carries tiny coils

• Those coils move in the field of a fixed magnet

• Motion induces voltage directly in the moving coils

So here the coils move, the magnet stays still.

MC cartridges usually have:

• Lower moving mass

• Often better transient/detail performance

• Much lower output in low-output MC designs

• Need for more gain or a step-up transformer / special phono stage

Typical output may be only a fraction of a millivolt for low-output MC.

8. The physics of signal generation

The key principle is electromagnetic induction.

If a conductor moves through a magnetic field, or the magnetic flux through a coil changes, a voltage is generated. The faster the change, the more voltage tends to be induced.

That means the cartridge does not respond to groove displacement in a perfectly direct way like a ruler tracing shape. It is more closely tied to motion dynamics, especially velocity. In practice, phono cartridge output is often described as velocity-sensitive over the audio range.

So:

• Groove modulation causes stylus motion

• Stylus motion causes cantilever motion

• Cantilever motion causes relative motion between magnet and coil

• Relative motion changes magnetic flux

• Changing flux induces voltage

That output is tiny, delicate, and easily affected by noise, capacitance, loading, and vibration.

9. Why the signal is so small

A phono cartridge produces a much smaller signal than a CD player, DAC, or streamer.

Typical levels:

• MM: around 3–6 mV

• High-output MC: maybe 1.5–2.5 mV

• Low-output MC: maybe 0.2–0.5 mV

A normal line-level input expects something much larger, often hundreds of millivolts to a couple of volts. So the cartridge cannot go straight into a normal AUX input and sound right.

It needs a phono stage.

10. What leaves the cartridge

The cartridge sends out:

• Left channel voltage

• Right channel voltage

• Ground/return connections

• Often a separate ground path from the turntable chassis/tonearm

This signal travels through tonearm wires, then RCA cables or similar, to the phono preamp.

Because the signal is tiny, cable properties matter:

• Capacitance affects MM cartridges strongly

• Hum pickup can be a problem

• Poor grounding can create 50/60 Hz hum

11. The role of the phono preamp

The phono preamp does two main things:

A. It adds a lot of gain

It boosts the millivolt-level cartridge signal up to line level.

Approximate gain needs:

• MM: maybe around 35–45 dB

• MC: maybe around 50–70 dB depending on output

B. It applies RIAA equalization

This is essential.

Records are not cut with flat frequency response. During cutting:

• Bass is reduced

• Treble is boosted

During playback, the phono stage does the inverse:

• Bass is boosted back up

• Treble is reduced back down

This playback equalization restores the original tonal balance.

12. Why RIAA equalization exists

RIAA equalization is used for practical reasons.

If bass were cut flat into the groove:

• Low frequencies would require huge groove excursions

• Playing time would shrink

• Grooves could collide more easily

If treble were not boosted during cutting:

• High-frequency playback would have poorer signal-to-noise ratio because surface noise and hiss would be more noticeable

So the industry standardized a pre-emphasis/de-emphasis curve.

During cutting

• Bass attenuated

• Treble boosted

During playback

• Bass boosted

• Treble attenuated

This:

• Saves groove space

• Improves playback noise performance

• Makes records practical

Without a phono stage, a record played into a normal input sounds:

• Too quiet

• Thin

• Tinny

• Lacking bass

13. Input loading: why the cartridge “sees” the preamp

The cartridge interacts electrically with the phono preamp input.

MM loading

MM cartridges are sensitive to:

• Resistive load, usually 47 kΩ

• Capacitive load, from cable + preamp input

Since MM cartridges have significant inductance, the capacitance can form a resonant circuit that changes high-frequency response. Too much capacitance can create a peak or rolloff.

MC loading

MC cartridges have much lower inductance, so capacitance is usually less critical. Resistive loading matters more. Different load values change damping and tonal behavior.

So the phono stage is not just amplifying. It is also part of the cartridge’s electrical environment.

14. Step-up transformers and MC cartridges

Low-output MC cartridges often need extra gain before the phono stage.

That can be done with:

Active MC gain stage

An electronic phono preamp with enough low-noise gain

Step-up transformer (SUT)

A transformer raises the cartridge’s tiny voltage passively before it hits an MM phono input

A SUT:

• Increases voltage

• Reflects an impedance back to the cartridge

• Can sound excellent when matched well

So an MC chain may be:

record → stylus → MC cartridge → step-up transformer → MM phono stage → line preamp / integrated amp

15. After the phono stage

Once the phono stage has:

• Amplified the signal

• Applied RIAA correction

the output is now standard line level.

From there it goes to:

• A preamplifier or integrated amplifier for source switching and volume control

• Then a power amplifier

• Then the speakers

The power amplifier increases voltage and current enough to drive the speaker voice coils.

The speakers then move air, recreating sound waves that correspond to the original recording.

16. The full chain in one line

Original sound wave
→ microphone/electronic source
→ recording/mixing/mastering
→ cutting lathe engraves modulated groove
→ record spins under stylus
→ groove moves stylus
→ stylus moves cantilever
→ cartridge generator creates tiny left/right voltages
→ phono preamp amplifies and applies RIAA EQ
→ line-level signal goes to amplifier
→ power amplifier drives speakers
→ speakers move air
→ you hear sound

17. Important mechanical factors that affect transmission

The path is simple in concept, but many things can distort it.

Tracking force

Too low:

• stylus mistracks

• distortion rises

• record damage may increase

Too high:

• wear increases

• suspension behavior changes

Anti-skate

Because of friction and arm geometry, skating force pulls the stylus inward. Anti-skate helps balance groove wall pressure so left and right channels track more evenly.

Alignment

Overhang, offset angle, and zenith alignment matter because the stylus is tracing an arc across a groove cut for a tangential cutter. Misalignment increases tracing distortion.

Vertical tracking angle / stylus rake angle

The stylus should sit at an angle close to the angle used during cutting. Deviations can affect detail and tonal balance.

Azimuth

The stylus should sit upright so each groove wall is read evenly. Bad azimuth causes channel imbalance and crosstalk.

18. Sources of noise and distortion in the chain

Several kinds of errors can creep in.

Mechanical

• Worn stylus

• Worn grooves

• Dirt in groove

• Record warp

• Rumble from bearing/motor

• Acoustic feedback from speakers into turntable

Tracing distortion

The playback stylus has a finite shape and may not perfectly follow sharp groove modulations, especially high frequencies and inner grooves.

Electrical

• Hum from grounding issues

• Cable capacitance mismatch

• Incorrect loading

• Noisy phono stage

• RF interference

Resonance

• Tonearm/cartridge low-frequency resonance

• Cantilever resonance at high frequency

• Body/tonearm structural resonances

19. Why vinyl playback sounds the way it does

Part of the vinyl sound comes from this electromechanical chain itself.

Unlike digital playback, vinyl involves:

• physical contact

• compliance and resonance

• analog groove geometry

• nonzero tracing distortion

• RIAA equalization

• cartridge loading interactions

That means the playback system is not a perfectly transparent “reader.” It is an active mechanical and electrical participant. Different cartridges, tonearms, phono stages, and setup choices audibly change the result.

20. A useful intuition

Think of the process like this:

The groove is a microscopic 3D road.
The stylus is the tire following that road.
The cantilever is the suspension link.
The cartridge is the motion sensor/generator.
The phono stage is the microscope and tonal corrector.
The amplifier is the muscle.
The speakers are the final moving surface that puts sound back into the air.

21. The most important distinction: phono preamp vs amplifier

People often say “amplifier” for the whole downstream electronics, but there are really two distinct stages:

Phono preamp

• designed specifically for cartridge output

• high gain for tiny signals

• RIAA equalization

• cartridge loading

Power amp / integrated amp

• volume control and source selection

• boosts line-level signal enough to drive speakers

A turntable without a built-in phono preamp must connect to:

• a dedicated phono input, or

• an external phono preamp first

Not directly to a normal line input.

22. In very compact form

The groove contains a physical analog of the waveform.
The rotating groove pushes the stylus.
The stylus moves the cantilever.
The cartridge converts that motion into a tiny electrical signal by electromagnetic induction.
The phono preamp boosts that signal and reverses the RIAA mastering EQ.
The amplifier then increases the corrected signal enough to drive speakers.

If you want, I can turn this into a labeled diagram of the whole signal path, or go even deeper into stereo groove geometry, MM vs MC cartridge internals, or RIAA equalization curves.