Analog to Digital Conversion

Analog Conversion

Have you ever seen this displayed on a CD or a vinyl record?

“This is a pure digital recording”

Well let’s stop right there.  First you must realize that a digital recording can be converted to analog for playback on vinyl, and that an analog recording can be converted to digital so it can be played back on a CD.

There is a lot of conversion from analog to digital and digital to analog that can occur in the process of recording and playback. So it really depends on where you begin the process as to whether it qualifies as a pure digital recording.  This is because the instruments generating the sound are still analog instruments, the transmittal of the sound from the instrument to the microphone still travels through the air in vibrations (air pressure pulses), and the microphone itself still “hears” analog vibrations which it converts into an analog electrical impulse.

The digital process begins at the point where the electrical impulses generated by the microphone are encoded onto a recording device. In the case of digital encoding, the first thing that must happen is to convert the analog electrical impulse into a digital code that represents the analog signal.  It is from this point, called the “Analog to Digital Conversion”, that the basic underlying debate really begins.

In order to “digitize” an analog signal, engineers developed a method of describing a sound wave’s attributes (frequency, loudness, waveform, etc) into a numerical code, a unique code for each particular “sample” taken. Keep in mind that the description is done for a particular moment in time, so if you have sufficient samples per second, and if your description is highly accurate then when played back this string of samples will sound very much like the original analog sound that it attempts to represent.

A good analogy always helps to visualize this process…

When you look at a picture on a TV you see a picture which looks a lot like the original.  But when you put your nose right up to the display you see the pixels that collectively represent the picture.

The more pixels used, the more accurate the description is.  In the case of a moving subject, the more frames per second, the more realistic and accurate the movement looks.  In the audio digital world this is analogous to the sample size and the sample rate.  As you can understand, the more accurate the descriptions are, and the more of these descriptions per second that are provided yield an image that will more closely represent the original analog signal, but it can never fully represent the analog signal because you can always improve on either the description or its frequency.

So why is digital so compelling if it cannot quite achieve 100% accuracy? The answer is that once a sound is digitized, the remaining process can be largely free of the problems that accompany analog recording and playback.

2 comments on “Analog to Digital Conversion

  1. GrewUpWithRecords on

    Your description of the digital recording and playback process is quite simplistic and incorrect. The comparison of digital audio output to looking at pixels completely misses the action of the analog output filter which takes out the “steps” in the sampled waveform, essentially removing the sampling “carrier,” as it were. What comes out are reproduced analog waveforms up to 22KHz (limited only by the sampling frequency choice).

    I grew up with records. I have one of the best turntables made. But records have so many problems that never really got solved, even though they had a run from Edison to the 1980s. The biggest was dust and dirt. There were many attempts to deal with this without much success.

    Also let’s add wow, flutter, hum pickup from the turntable motor to the magnetic pickup, stylus wear, groove wear, variations in vinyl quality, resonances in the tone-arm/cartridge-cantilever combination, cosine distortion from off-center records. skating and inner-groove harmonic distortion, vibrations picked up from the motor (rumble), speaker feedback, skipping from footsteps, skips from over-cutting, surface noise, limited dynamic range, scratches and record warpage.

    CDs were a quantum improvement over records. Anyone who thinks otherwise most likely never had to put up with all the problems of vinyl. Theirs is just a romantic longing for a “simpler” age they never actually lived in.

    • Ron on

      Well, you certainly have put forward a typical “digital is better than analog” argument. Hopefully someone who feels equally strong about the superiority of analog over digital will come forward with a statement of their own.

      But for now, let me comment about your post:

      My goal with these posts is to put the “analog vs. digital” into understandable terms for a non-technical reader. Despite my best efforts my writings were still criticized for being way too technical for some readers. My use of the visual world for analogies in the aural world certainly do fail (like all analogies fail) when taken too literally. But my point about sampling size and rates still holds water however. A larger sample size along with more frequent samples makes for a better digital representation. As this presents itself in the digital world I can accurately say that the DVD-Audio specification is vastly superior to that of the CD specification with regard to accurately representing a sound. I can also say that vinyl records have more potential information than the CD spec provides for. I can also say that any digital specification, no matter how good, can always be improved upon and never fully captures the native analog sound. This is analogous to reducing the distance to your goal in half; no matter how small it gets you can still cut the distance in half again and will never reach your goal. Any digital will never equal the native, analog sound, it can only approach it and approximate it.

      You have certainly made a good list of the problems with analog recording and playback. These problems do exist, but these issues can be “halved” just like the problems (that you didn’t mention) with digital representation can be minimized. So after all is said and done, digital comes up slightly short of the native analog sound while an analog representation has a bit of unwanted extra stuff (noise, wow, flutter, etc). Both can approach equaling the native sound and are close enough to make the point moot when considering that it has to be played back through equipment that will introduce way more distortion than the shortcomings of analog or digital.

      For me, the real world is always full of unwanted noise, so if an analog recording has some in there it just sounds more natural to my ears. Conversely, digital has always struck me as being so sterile, lifeless, and unrealistic. Personally I am good with both analog and digital existing side by side. But I can honestly say that I prefer listening to non-digital recording and playback. I say, to each his own.


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The Classic Vinyl Listening Experience

  • History

    Intro To The Classic Vinyl Listening Experience

    Welcome to the Sound Exchange reference guide about vinyl records. On these pages we will explore any and all topics that are relevant to the enjoyment of vinyl records. Read more...

    The Emergence of Long Play (1948)

    The Classic Vinyl Listening Experience began with the emergence of the 10” and 12”, 33 1/3 rpm, Long Play, Micro-Groove, Vinyl Record in 1948, and its smaller sibling, the 7” 45 rpm record. Read more..

    Modern Long Play Records

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    The Modern Vinyl Record (1960s)

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    The Classic Vinyl Listening Experience Timeline

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  • Analog Vs. Digital

    Which is better, CDs or Vinyl Records?

    This question can be reduced to studying their differences. Read more..

    How Sound is Created and Heard

    This discussion begins with the creation of sound itself. Everything in nature that creates a sound creates an analog sound, which also happens to be the only kind of sound that we can hear. Read more..

    Analog to Digital Conversion

    The digital process begins at the point where the electrical impulses generated by the microphone are encoded onto a recording device. Read more..

    Playback Pros and Cons

    An analog recording doesn’t attempt to describe the sound as it simply records its input continuously, so it doesn’t have the sample size and sampling rate issues that digital has. Read more..

    What about CDs?

    First you must remember that the specification for CDs was developed way back in 1979. Read more..

    My Thoughts on Digital Vs. Analog Sound

    The vinyl record is my preferred media for active listening to recordings made in the 1950s and into the 1980s. Read more..
  • Stereo Recordings

    Stereo Recordings

    Any discussion about music and sound reproduction will eventually make reference to how it is presented to the listener. Read more..

    Stereophonic Recordings (1960s)

    Regarding stereo recordings, when stereo first came out it was a brand new world and exactly how to represent a recording in a stereo format was very subjective. Read more..

    Mono Vs. Stereo Recordings

    Beginning with the comparison of Mono and Stereo recordings, it was typical that both mono and stereo records were made from the late 1950s until around 1970 when they ceased production of mono records. Read more..

    Quadraphonic Recordings

    Finally let me touch upon quadraphonic recordings as they appeared on vinyl records. Read more..
  • Turntables

    The Record Player

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    Anatomy of a Turntable

    The turntable has several basic components including the plinth (base), the revolving platter, the tone arm, the cartridge and stylus, and the mechanical and electronic components to make it all work. Read more..

    Reducing Unwanted Noise

    Isolating the noise generated from the turntable’s motor from the platter is essential. Read more..

    Choosing a Quality Turntable

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    Turntable Belt Replacement

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    All about Phono Cartridges

    At the heart of any turntable system is the phono cartridge. Read more...
  • Other Stereo Equipment

    Classic Stereo Equipment

    Stereo equipment is one more significant variable that can greatly affect the Classic Vinyl Listening Experience. Read more..

    Phono Preamps: Amplification and Equalization

    When the discussion turns to the phono preamps (short for pre-amplifier) we are really getting down into minute details of the record groove in order to understand its role and its importance. Read more..

    Purchasing Quality Preamps

    Like all components of a stereo system there are significant variations in quality in the preamps, which has significant effects on the quality of the playback of your records. Read more..
  • Records

    On First Pressings

    Typically, a first pressing is defined as what the actual record album looked like when it first came off the manufacturing line. Read more..

    Grading the Condition of Records

    At Sound Exchange we use visual grading (as opposed to play grading) for our records. We do not grade jackets, only the vinyl itself. Read more..

    About 78 rpm records

    The 78 rpm record was the primary format for music sold during the period from the early 1900s into the 1950s. Read more..

  • Taking Care Of Your Records

    Record Storage

    Always store your records in a cool, dry, dark environment in an upright position (never flat) that is high off the ground, and that provides some airflow around them. Read more..

    Tips for Handling Records

    Always handle your records by the label and the outer edge and never ever touch the record grooves except when performing a deep cleaning. Read more..

    That’s Not a Scratch on Your Vinyl – It’s Dirt!

    Dirt and static electricity may cause good records to sound “scratchy”. A proper cleaning will remove dirt and static electricity from the vinyl. Read more..

    How Often Should Records Be Cleaned?

    Record cleaning, like most any other type of cleaning, is a matter of degree. Read more..

    Record Cleaning Solution

    Wet cleaning of vinyl records is the best way if not the only way to really get them clean and to get them free of static electricity. Read more..

    How to Clean a Record

    Use plenty of solution and really get the record wet while being very, very careful to keep the solution off of the record label, as it will cause the paper label to “rise” or stain the label, etc, and it will never look like new again. Read more..

    Salvaging Vinyl

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