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Analog vs Digital Audio [What's better?]

Audio Basis - educational articles

yuri korzunovMany disputes, what is better analog or digital audio signal, can digital sound as good as analog, are continued despite digital devices successfully and rapidly replace analog ones. There is opinion, the main difference between digital and analog audio is analog closer to an original. It looks like, the analog waveform is smoother than "stairs" of digital music. On the other hand, a digital signal is not "stairs" actually. Not all is quite so simple. Read to end the easy and detailed explanation by audio software developer Yuri Korzunov.

Frequently Asked Questions

For quick entry to the topic, read frequently asked questions. After it, read full article to better understanding what is better analog or digital audio and why.

Is analog better, than digital? Which is better analog or digital recording?

Technically, digital systems and records (its mediums) is capable cause lesser degrading sound issues, than analog ones.

The analog degrading cause sound "colorization", that may sound "nice" subjectively.

Other hand, digital systems have different quality due various implementations. And important features of a digital system may be worse than similal features of an analog one.

Example: if a digital system have frequency limitation on 16 kHz, it may sound worse than analog system with 18 kHz limitation.

Resume: What's better analog or digital is matter of personal taste and available system.

Read more about abilities and issues of digital systems here...

 

What is the difference between analog and digital signal?

Digital signal is form of coding of analog signal.

Read details...

 

Which is better analog or digital signal?

Digital signals have zero losses in communicaction channels and on mediums, in most cases. It achieved due to special coding and recovering ability with probability close to 100%.

Analog signals are distorted in the channels and in mediums due to noise, crosstalk and other interferences, mechanical issues.

Of course, if we compare original analog sound with analog one, that restored from digital record [of the original], we get a difference.

But if we compare the original and its analog record, the difference will be more.

Read more...

 

Is analog or digital more reliable? Why is digital better than analog for transmitting data?

Digital signal is more reliable to distortions due to special coding and recovering abilities. See more...

 

What is the digital audio output for? What is digital audio output in TV?

Digital audio output send audio signal in a digital form. It used on different devices like digital audio CD/SACD/DVD-players, AV-receivers, TV.

 

Is digital audio output is better then analog?

If you have alternative between digital and analog output at a device (CD-player, as example), it means, that the device have built-in DAC (digital-to-analog converter). You can use its analog output.

Alternatively, you can use digital output. If external device (DAC, AV-receiver) have better DAC, it can give sound advantages.

But, some digital outputs may have sample rate/bit depth limitations by technical or other issues. And external DAC will not used fully.

Also, an external DAC may have resolution limitations on its own.

So before the decision, learn:

  • the actual resolution abilities of available digital output and DACs;
  • compare analog output sounds of the device and external DAC.

 



What is the difference between analog and digital audio?

Analog and digital audio

Analog and digital audio

We can see, that digital signal is a virtual math model of an analog signal in the digital domain. I.e., despite, the digital signal consists of separate samples, and the first wish is to connect lines in the "stairs", a discrete digital signal is continuous waveform math point of view.

If we ideally upsample digital signal to the infinite sample rate (interpolate/restore virtual samples between real samples), the digital waveform will be uninterrupted and equal to analog one.
The connection line is the same to steel ruler, that fixed in the points of real samples.


The same way is restoring a digital signal to analog form. There we get a continuous signal for any sample rate.
It happens, because the analog filter of a DAC is ideal interpolator, that smoothly and correctly connect digital samples.
We can see it in the picture above.

 

Sound quality

In the article, we'll consider what is better sound quality: digital or analog?

Sound quality has 2 definitions:

  1. Level of distortions - the lower level is better audio quality;
  2. Subjectively estimated sound quality.

Sound quality definitions

Sound quality definitions

 

Both audio types have the same source - analog musical or another signal.

However, the next stage is storing and reconstruction to played back an analog signal. And the stage causes different losses for various audio systems. We can compare an analog vs digital system at this stage only.

 

Sound quality measurement

Definition #1 (distortion level) depends on the sensitivity, accuracy, and precision of a measurement tool.

Definition #2 (ear test) can be partially free from subjective biasing due to big numbers. Measurements are provided via blind tests. However, it is not a simple procedure.

Measurements

Distortion-level sound quality and ear-test sound quality may be uncorrelated in some cases. It happens, because various patterns of the measured distortions may impact differently to ears and brain.

EXAMPLE:

Even, a higher level of distortions is not meant better-perceived quality in ear test.

There are tricks in mixing and post-production, that can improve the sound, despite altering the original sound.

The author would compare the original sound and sound, containing some "nice-sounding" distortions, with "tomato juice" and "tomato juice with pepper and salt".

Allegory of sound improvement via distortions

A few salt and pepper may improve the juice taste. No seasoning is "dry sound". Too much seasoning is "dirty sound".
Different improvements may be there. They depend on personal taste.

May be natural notes of original juice, hidden by the seasoning, are preferable for some people.

Look an infographic of analog vs digital audio quality comparison, where essential factors are shown.

Analog vs Digital Audio Comparison
(click for enlarge)

Analog vs Digital Audio Comparison

We can see, that before the original acoustical signal comes to medium, it pass through electro-mechanical (microphone) and electrical devices. To throw out factors, that common for all systems, below we'll consider original electrical signals directly before and after the mediums (tape, vinyl, digital unit) and its conversion devices (tape heads, vinyl recorder and player cartridge, including circuits, ADC, DAC).

 

Analog audio quality

Let's consider an analog audio system.

 

Mechanical issues

A vinyl recording is produced mechanical way (see simplified workflow):

  1. Special stylus at a grooving machine cut grooves at a master disk according to an original electrical signal;
  2. A nickel stamping record is produced from each side of the master;
  3. At a pressing plant, vinyl LP disks are pressed to distribution.

In each of the stages, some mechanical deviations appear.

Production of vinyl disks is not ideal too

Production of vinyl disks is not ideal too

"Wow and flutter"

"Wow and flutter" effect is caused due to rotation speed deviation or magnetophone tape stretching.
The speed deviation alters the time of playback of the same tape or groove length. It causes frequency bias, that leads to total waveform distortions.

"Wow and flutter" effect. Waveform distortions

Wow and flutter effect

The speed deviation happens during recording and playback.

Temperature

Mechanical processes are sensitive to environmental temperature. As an example, it can cause an altering of play in bearings. The play may cause variations of "wow and flutter" effect.

Wear and tear

With wear and tear of the mechanical parts, audio parameter precision and accuracy degrade. It can cause increasing of distortions.

A tonearm angle altering

When a tonearm playback LP disk grooves at different distances from its center, angle of a stylus tip relative the groove is changed. It alters playback characteristics. The issue may be partially solved via tangential tonearm, that moves to the LP center with constant angle. But any mechanical device has parameter deviations, that impact to sound.

Tangential tonearm

Tangential tonearm

 

Noise

The main issue of analog mediums is noise.

Vinyl disks are sensitive to dust. It causes temporary mechanical distortions of the disk surface. The disk cleaning is very desirable.

Vinyl and dust

Vinyl and dust

A tape has noise due to magnet layer physical processes. There are some noise reduction systems. But it can't extremely reduce noise, like digital systems.

Tapes and vinyl records also wear and tear with storage and/or using time. Vinyl disks may be warped, scratched. Tapes may be stretched, well-worn and degaussed.

Analog noise

Analog noise

 

Electronic components

Electronic elements (transistors, tubes, others) of analog musical devices wear with time. Values of the element's parameters may come out of allowable range and lead to higher non-linear distortions and other.

Electronic components are a source of analog noise.

Degrading of electrical, magnetic, mechanical parameters also touch cartridges of LP players and tape heads.

Electronic components

 

Loudness limitations

In general, analog mediums put more loudness limitations for recorded audio stuff, than digital ones.

EXAMPLE:

LP has a limitation on an album track width (time length) at the disk side. A mastering engineer can control the record grooves and the track width by volume altering. But, when several tracks are located on one side of the disk, a similar volume should be provided.

Vinyl grooves

Vinyl grooves

Digital recordings have lesser issues with loudness and its normalization. Because even popular 24-bit formats have a wide dynamic range for recording. 32- and 64-bit float point formats have extremely low noise level and overload tolerance for audio processing.

 

Overload and clipping

Output analog signal is limited by the maximal level. Close to the level, non-linearity is increased dramatically and output signal can't grow above the level despite the input signal is rising. So, the output waveform is distorted.

Analog overload and "soft" clipping

Analog overload and "soft" clipping

It's called "overload". And such output waveform distortion is called "clipping".

At the picture, we can see the smooth transient-clipping zone in point A. Such transient type leads to "soft" clipping of output waveform.

As rule, analog signal cause soft clipping - linearity is decreased smoothly.

 

Digital audio quality

Let's consider a digital audio system.

All its parts, that conduct or convert, from/to analog signal, cause phase, frequency, non-linear distortions.

Electronic elements of analog parts of the digital musical devices wear with time like the same items in analog systems.

Digital sound quality

 

Clock stability, jitter

Stability of the clock signal of ADC (analog-to-digital converter) and DAC (digital-to-analog converter) is very important. There are deviations:

  • frequency;
  • phase and front steepness (jitter).

The issue may be considered as similar to "wow and flutter". But, currently, digital-system clock stability is very high, comparing speed deviation of analog systems, in most cases.

Jitter in digital audio

Jitter in digital audio

 

Digital power amplifiers

Digital music systems may not be pure "digital". Because humans can receive analog acoustic waves only. But, in the author opinion, we have some trend to reduce the analog part share in audio systems.

D-class power amplifiers, based on sigma-delta modulation (like DSD), exists a long time. But they still not popular enough despite these amplifiers allow to get rid of digital-to-analog converters (DAC) and are fine compatible with the DSD.

Digital vs analog power amplifiers

Digital vs analog amplifiers

Digital overload and clipping

If no additional processing, overload in digital format cause loud click due to positive value transformed to negative one momentarily.

Traditional digital overload and strong waveform damaging

Traditional digital overload and strong waveform damaging

 

Fixing of digital overload issue via compressor/limiter in the analog domain

Fixing of digital overload issue

To avoid digital overload, analog compressing and/or level limiting of an input signal of ADC (analog-to-digital converter) may be applied.

Special processing provides traditional clipping into the digital domain. The clipping may be:

  • momentary or
  • soft, like analog.

Momentary digital clipping (safe digital overload)

Momentary digital clipping (safe overload)

"Soft" digital clipping (analog overload emulation)

"Soft" digital clipping (analog overload emulation)

Overload may be avoided via analog compression of input analog-to-digital converter's signal.

When overload might occur into the digital domain, float point formats may solve the issues. The formats provide 0 dB level for 1.0.

If overload happens (1.1, as an example) it will not be clipped. At the final stage, the overloaded peak level may be normalized back to 0 dB.

How to avoid digital clipping in float point format

How to avoid digital clipping in float point format

 

 

Digital vs analog sound quality

Digital versus analog audio systems

  Analog air, wires Tape Vinyl Digital air, wires Digital CD, DVD, SACD Digital lossless Digital
lossy
Noise level Depending on modulation (FM, AM) in interference surround about -60 dB about -70 dB depending on bit depth and recovering abilities depend on bit depth, modulation (DSD/PCM) and ADC abilities depend on bit depth and ADC,
-96 dB and better
depend on compression method and bit depth
Clicks depend on interference no yes depend on interference depend on interference, wear and tear/scratches, and optical-mechanical factors, a reading device almost improbable in memory and files
Medium speed deviations (slow deviation) no yes no
Jitter (fast deviation) FM/AM-modulator may cause phase instability no yes; as rule, defined by ADC and DAC only
External mechanical impact no, except physical cable damage insignificant significant no, except physical cable damage insignificant no, except impact to a mechanical hard disk drive
Temperature impact

impact to radio wave propagation, wires; on wires may depend on the length

yes impact to radio wave propagation, wires; on wires may depend on the length almost no don't impact to files
Recovering abilities for damaged audio information no yes with special coding
Impact of power stability and noise yes
Time degrading no, except cables yes no, except cables insignificant no, except physical medium or device degrading
Sensitivity to mechanical damage only wires yes only wires may be compensated via recovering in some cases depend on device safety, may be compensated via recovering in some cases

 

Analog vs digital audio outputs

What is most recommended: analog and digital audio outputs? Before answer the question let's consider the scheme.

Analog vs digital audio outputs

Analog and digital audio outputs

We can't see a significant difference between paths from the digital mediums to analog devices at upper (analog output of the digital device) and lower (digital output) parts of the drawing.

Factors impact to sound quality:

  • DIGITAL CABLES: Length is a significant factor, impacting to losses in the cable. However, if digital cable doesn't cause pauses, interruptions, pops and other audible issues, it's length do not matter.
     
  • ANALOG CABLES: Length of analog cable impact to sound smoother way. It can aggravate frequency responses. But, it's not dramatically.
     
  • DIGITAL-to-ANALOG CONVERTER: DAC implementation may impact to sound quality. External DAC device can't guarantee the better sound quality, comparing builtin one.

 

Connection via digital vs analog outputs

  Digital connection Analog connection
Interruptions, pauses, pops long cable length, damaged cable damaged cable
Sound transparency doesn't impact to sound quality may impact to sound quality
DAC impact to sound quality

 

Analog connector types

Type May be unbalanced May be balanced Description
RCA yes no As rule, for home applications.
TRS (jack) yes yes Implementations: jack, mini-jack, micro-jack. As rule, for music production and performance applications.
XLR yes yes As rule, for music production and performance applications.

In general case, no difference for sound quality between these connectors. However, a balanced connection may improve the signal-to-noise ratio. It may be important in hard electromagnetic interference environment and for long cables. A necessity in balanced connection is defined experimentally by ears or measurements at an audio device output.

Digital connection types

Type Total throughput, Mbit/s Supported resolution audio Max. length, meters Description
SPDIF about 9.2 (audio data without meta-information) 24 bit/192 kHz, stereo/multichannel(compressed). Channel number depends on sample rate 10  (optical)/15  (RCA)  
USB up to 3 200 (USB 3) Depend on maximal throughput of the USB-interface version 3 (depend on USB-interface version)  
HDMI up to 18 000 (HDMI 2.0) Sample rate up to 768 KHz for 2 channels. Channel number (up to 32) depends on sample rate 15 (depend on maximal throughput)  
Thunderbolt up to 40 000 (V3) Via DisplayPort protocol. Sample rate up to 768 KHz for 2 channels. Channel number (up to 32) depends on sample rate (v.1.4) up to 2 (depend on supported options)  

Meta-information is data about transmitted information.

Below we can see throughputs for different audio resolutions. It should be lesser than the maximal throughput of a digital connection with an accounting of the meta-information.

Throughputs of audio resolutions

  Bit depth, bit Sample rate, kHz Channels Bitrate (uncompressed), Mbit/s
1 24 96 2 4.608
2 24 192 5.1 27.648
3 32 384 2 24.576
4 32 768 2 49.152
5 1 DSD64(2.8 MHz) 2 5.645
6 1 DSD64(2.8 MHz) 5.1 16.934
7 1 DSD1024(45.2 MHz) 2 90.317

 

Read more about audio interfaces

 

Analog versus digital mixing and gain control

Most popular audio editing are analog mixing and gain control. The mixing and gain control are implemented in analog circuits and components (transistor, tubes, operational amplifier, and others).

Analog and digital mixing

Digital audio is a form of analog audio coding. From a math point of view, no difference between analog and digital gain control. Look at the formula of gain control for both digital and analog audio:

output(t) = input(t) * gain,

where t is time.

At first glance, digital values are discrete and cause precision losses.

But, a digital signal is not "stairs". We should consider it as a continuous function with some bit depth, that causes a certain noise level.

Using float point math to gain control allows to apply gain and mixing transparently for audio stuff.

Gain control

It is necessary to remember, if we multiply 16-bit integer values, the result should be placed to a 32-bit integer value and truncated back to 16 bit. After all processings, dither is recommended.

Result of multiplication of two 32-bit float values is 32-bit float value.

Analog gain control may be implemented in different ways. As an example, a switchable resistor kit can provide dB-scaled gain control.

1...2 dB-step implementation is significantly easier in float point formats, comparing 16/24-bit integer variables.

Using electronic components in gain control circuits cause non-linear distortions, noise, temperature instability.

But, for level adjusting of:

  • analog devices in a pure analog system, or
  • digital units, to avoid reducing of actually used bit depth (dynamic range),

analog gain control may be used.

Digital vs analog mixing and gain control

  Analog mixer Digital mixer
Noise level about -60...-130 dB or worse (depend on electronic components, construction, signal sources) about -180 ... -200 dB and better (for float point formats)
or worse for 16/24 bit
Non-linear distortions yes no
Overload yes may be avoided (depend on the implementation and sources)

 

Resume:

Except for artistic purposes, analog mixing is not recommended for high fidelity music production.

Digital gain control, when it applied properly, is more precise when analog one and cause lesser issues.

In, some cases, we can apply analog gain control only.

 

 

Analog vs digital audio production, recording proc and cons

Analog vs digital audio production, recording proc and cons

Analog vs digital technologies in music and audio production, recording

  Analog Digital
Noise level higher lower
Parameter stability of full production system lower higher
Mechanical distortions yes no
Distortions in recording higher lower
Distortions in editing higher lower
Pre-ringing of filters no yes; no for minimum-phase filters
Post-ringing of filters yes yes, approximately double post-ringing energy for minimum-phase filters, comparing linear filters with pre- and post-ringing
Temperature, wear and tear, interference stability lower higher
"Artistic" distortions and "analog" sound (vinyl, tape, tubes, analog compression, synthesizers,...) yes software emulation
Project saving high cost, sophisticated electro-mechanical drives of sliders with same positioning error yes
Precise/exact project saving no yes
Lossless backup no, time degrading by different reasons yes
Lossless copy (including factory) no yes
Copying protection no optionally
Distribution only physical delivery network, memory devices, physical delivery

 

Are speakers analog or digital?

In the general application, a speakesr are pure analog device. There are drivers with passive electrical components.

But some speakers contains amplifier(s) inside. Teoretically, it allow:

  • achieving better adjusting the amplifier with driver(s),
  • applying active (at active electronic components - op-amps, transistors) crossovers with higher abilities.

The amplifier may be digital.

The crossover may be implemented in the digital domain, that give more potential abilities, than crossover on the active components. But, DSD-input signal demands additional tricks for editing (EQ, gain contlrol). If the editing is done properly, it is almost transparent for the audio signal.

 

Analog versus Digital. Conclusions

  1. Analog mediums have serious electromagnetic, electrical and mechanical, aging, environment issues that degrade stored and played back audio signals.
    Engineers try to reduce negative mechanical effects of analog devices in different ways. But, according to invention theory and practice, the best way to get rid of an issue is to get rid of the issue source. I.e. removing mechanical parts automatically remove their issues.
     
  2. Digital systems have some degrading issues too. Primarily into analog parts or when digital audio is converted to/from analog signal (jitter, non-linearity, etc.).
    Lower bit depth and sample rate may cause sound quality degrading. But, even, minimalistic 16 bit / 44.1 kHz is good enough, the best analog sources. Of course, implementation as analog as digital units is matter.
     
  3. In the digital domain, audio may be successfully restored after damaging, when special coding is used. Degraded analog stuff cannot be restored.
     
  4. The workflow of digital music production and distribution is significantly easier, than analog mediums and provide lesser distortion level.
     
  5. On the other hand, specific distortions of analog mediums (tape, vinyl, tubes) may have artistic character, that сan give an impression of better sound.

Analog vs digital audio

 

Read more:

 


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