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Understanding Analog & Digital In Terms Of Audio
Neither analog or digital is "better" or "best". An uncolored look at the underlying simple truths of both formats.
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This is achieved through an analog-to-digital converter, utilizing sampling and quantization.

How You Slice It
Sampling and quantization is like looking at the speedometer of your car. If you don’t keep a regular eye on your speed, your car might be going faster or slower than you realize.

Audio sampling is simply taking regular measurements of a varying analog voltage or current.

Because the audio voltage or current is constantly changing, we have to pick moments in time to freeze the audio as a non-varying number.

We must make measurements in a quick enough succession that we don’t miss important changes between measurements.

And we must measure with enough resolution that we capture as much detail as we desire.

Theory tells us that the rate at which the signal is sampled must be at least twice that of the highest frequency that we wish to reproduce.

The Nyquist Theorum, therefore, means that, to faithfully capture an analog audio signal that extends to the accepted upper threshold of 20 kHz, it must be sampled at 40 kHz, or 40,000 samples per second.

As an aside, the reason that the compact disc Red Book standard dictates a sampling frequency of 44.1 kHz is based on the early developers, Philips and Sony, wishing to cover the generally accepted audio spectrum of human hearing while also fitting the resulting digital information onto videotape.

By fitting three samples into each active line in the video field, at 50 Hz or 60 Hz, the developers were able to sample 44,100 times per second and save the data onto videotape, which was the digital audio storage and mastering precursor to the compact disc.

These days, we understand that the higher the sample rate, the better. Extending the sampling frequency well beyond the minimum 40 kHz allows digital processing tools to operate on the signal without compromise and to reduce alias signals.

Alias signals are basically components of the audio signal above the upper limit of the sampling frequency that are essentially folded back into the signal, creating an unpleasant distortion.

Someone once gave a good example of aliasing. A guy living in a cave was waiting for daylight. He stuck his head outside about every 25 hours.

Starting at 8 o’clock at night (8 pm), he next looked outside 25 hours later when, unbeknownst to him, it was 9 pm and still dark.

Poke your head out of a cave once every 25 hours or so, and you’re going to get an incorrect sampling of day-to-night ratio. So it goes with digital sampling.

Looking outside his pitch black cave every 25 hours he encountered night 10 times in a row, leading him to believe that the night was 10 times longer than it really was.

That is what aliasing is all about. It’s a false reality, created by not sampling the signal of interest frequently enough. If the knucklehead had looked every hour he would have seen the true length of night.

The same goes for audio sampling. If we don’t make enough measurements within a period of time, we miss important audio information and end up with incorrect sounds, harmonically unrelated to what we really wanted to capture.


Comments (5) Most recent displayed first | All comments in chronological order
Posted by George S. Louis  on  11/28/11  at  07:06 PM
FYI about polarity at the link: http://www.ultrabitplatinum.com/?page_id=725 . If you find that interesting, I can send you a text only version sans commercial references. You may also find my think pieces about polarity and imaging at: http://www.ultrabitplatinum.com/?page_id=88 and at: http://www.ultrabitplatinum.com/?page_id=1513 interesting as well, or not.

If you'd help me sort out the mistakes, when and if they're corrected, you just might become an instant overnight music-lovers' folk hero. Or on the other hand be tarred and feathered and have your ears cut off and served up to you on a silver platter for your last meal as an audiophile guru. I invite you to visit so that I can take you out for a meal on me and then we can share some of your music and mine on my custom built (by me) audio system on a CD player with a digital domain remote controlled polarity switch. My system is the best I've heard so far for discerning polarity that still must be done by ear. Those who hear CDs played over my system don't usually have much trouble hearing polarity. But whatever happens it will be just between the two of us, if that's what you prefer. It'll be attorney client privilege, or Perfect Polarity Pundit privilege, you decide. But ultimately for the sake of the music, it's up to you to either be part of the problem or part of the solution, so that 30 years doesn't become 31. Besides email you may also call me 7 days a week at 619-401-9876 or toll free at 888-588-9542 between 9AM and 11:45PM Pacific Time.

Best regards,

George S. Louis, Esq., CEO Digital Systems & Solutions Email: gslouis@gslouis.com Website: www.GetBetterFidelity.com Phone: 619-401-9876 1573 Kimberly Woods Drive El Cajon, CA 92020-7261 P.S. How difficult would it be for companies' voice menus instead of saying "Please listen to the entire announcement because our menu has changed recently before making your selection" to "Our announcement was last changed on such and such date? And that would also save time and electrical energy.

Posted by Alexander Jenkins  on  11/28/11  at  04:50 PM
My comment of respectfully disagreeing with the "comment above" refers to Zal's expression of analog not affecting the sound, not the article.

PS , if I misunderstood Zal's comment, then simply take my thoughts as a general comment.

Posted by Zal  on  11/28/11  at  04:50 PM
As a mastering engineer, we once had a shootout with 3 top A to D converters...one sounded best but I noted that another sounded the most like the original analog master tape, and that's the one we chose to master with.

While I am well aware of the changes that can occur with different gear, and there are times when this is efacacious, we were looking for the most accurate to the original.That's the situation I was referring to.

As a musician, I know that when it comes to a Jazz piece (in general) you start out with the original melody and them embellish, and take off from there...but if you start off in an altered state, it's hard to get back to the original (at least enough to appreciate it after the musical astral travels). Of course, the analogy is a bit flawed here as the musicians COULD choose to go back to the original melody somewhere in the song, but, if we are talking about capturing the purity of sound, once it's altered, there is no turning back.

Posted by Alexander Jenkins  on  11/28/11  at  04:42 PM
Great article. Fun to read.

As a medical professional once stated, "every medication has side effects. There isn't a medication made that is truly transparant to the body". Such it is with anything we use to capture or process sound. So to respectfully disagree with the comment above, when using analog to capture the sound as close as possible to the "real thing", I also use it to alter/color the sound as the article suggests. While it may not be processing using 1's and 0's, it still adds color which distorts (alters) the sound from the original. For instance I use a dynamic mic on a snare because inertia from the sound pressure of a snare hit causes the diaphragm to continue motion beyond the natural length of the sound coming from the snare. This lengthened sound is artificially created due to the inability of a dynamic mic element to stop fast enough. So while the sound is still "analog", it is now like the artificial crab example in the article. I like the taste of both and am happy to have some great analog and digital options nowadays. Even the digital remakes of analog processing, which while close to the originals and even if spec-wise appear to react exactly the same, still have a new character of their own.

Posted by Zal  on  11/28/11  at  03:25 PM
While it all starts as analog, it also all ends as analog, or you just won't hear it.

And analog doesn't have to be recorded or processed to sound good, it just sounds natural just the way it is while digital is meant to mimic that natural nature of analog. Analog sound doesn't have to mimic anything....

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