Is Digital Audio Transmission Analog? [video]

[Ken Tajalli]

What??? The example of indicators was yours.

That's what I meant.
I knew that example was exaggerated, I was trying to make the point.
Since absolute square wave does not exist is a real world, as many have correctly pointed out, then any square wave in real world is accepted to be imperfect.
At what point a square wave is considered to be no longer a square wave?
Always? or is it application dependent.

 

[DonR]

That's what I meant.
I knew that example was exaggerated, I was trying to make the point.
Since absolute square wave does not exist is a real world, as many have correctly pointed out, then any square wave in real world is accepted to be imperfect.
At what point a square wave is considered to be no longer a square wave?
Always? or is it application dependent.

Like most things when it is "good enough", which is thoroughly application dependent.

 

[Axo1989]

Some newer cars slow that signal so the LED's aren't so abrupt in action.

So, sounds like vinyl? Or tubes. Smooth ...

 

[pablolie]

That's what I meant.
I knew that example was exaggerated, I was trying to make the point.
...

It's called a "strawman argument" in the discussion of logical fallacies, though.

I for one can't comprehend how a discussion about perfectly shaped squares (which no one ever needs a digital signal to be) relates to digital audio anything. We engineers use formulas to model all the time - and models don't have to represent a fundamental natural truth, they merely have to work in the real world. Anyone that thinks F = m*a will question if Newton was a moron given relativity and quantum physics, but the fact is that the formula works perfectly in its domain. Engineers couldn't be any less interested in fundamental, universal natural truths. [Of course it helps to understand domain-specific physics very well].

A much better example in this is the history of telephony. It was once totally analog. Not only did it make it a beast when it came to maintenance and offering new capabilities (conference bridges, 800 services, and no data services anywhere), but the signal transmission itself was horrible. You needed plenty of repeater you had to painstakingly match, you needed to do echo-canceling stuff to avoid signal reflections - nasty stuff. How they did it is totally beyond me. And voice quality in long distance calls sucked brutally and half the time you'd get other conversations modulated into yours. Do you want that tech in your audio chain at home? <- that is a logical fallacy as well . That's why digital telephony came along - voice quality is now better than ever etc etc

 

[Ken Tajalli]

It's called a "strawman argument" in the discussion of logical fallacies, though.

I am finding this interesting and amusing, So I will reply.
Strawman? nah ,
it has been argued that square waves are made of sine wave components, I was arguing that a square wave may be broken down to sine wave components, but THAT doesn't mean the square wave was composed of them, in an application based, real world.
A square wave in a car indicator system is a very simple example of that! The current is surely a square wave, it does not contain any sine waves, nor within that application, sine waves are relevant.
Now if you put that square wave into an analyser, you will see that it is not perfect and detect sine wave components, but who cares?
Within car indicator application, we have our square wave, period.

I for one can't comprehend how a discussion about perfectly shaped squares (which no one ever needs a digital signal to be) relates to digital audio anything. We engineers use formulas to model all the time - and models don't have to represent a fundamental natural truth, they merely have to work in the real world. Anyone that thinks F = m*a will question if Newton was a moron given relativity and quantum physics, but the fact is that the formula works perfectly in its domain. Engineers couldn't be any less interested in fundamental, universal natural truths. [Of course it helps to understand domain-specific physics very well).

It is argued that once a digital pulse or square wave enters a conductor, it becomes analogue because it no longer is a perfect square wave (or pulse). I am arguing that within hifi (not telecom, not TV transmission, not ultra high data rate, not ....) digital audio transmission through a conductor, with in short distances (remember Hifi environment ) the pulses, the square waves are, indeed square!
Any deformations/deviations because of the conductor, for as long as the receiver can lock on to the data stream and capture it, are irrelevant.
I am arguing that the notion that square waves do not exist in the real world, and all are composed of sine waves in all environments and applications, is false.
Within reason and within the scope of the application, square waves do exist.
I do understand Fourier analysis, and that mathematically a square wave can be broken down to a series of sine waves, but that blanket, mathematical definition does not apply to a car indicator system. Hence why I used it.
enough for tonight - If by now I have not given anyone food for thought, then I am wasting my breath and your times.
With respect and thanx to all who replied.

 

[fpitas]

I am arguing that the notion that square waves do not exist in the real world, and all are composed of sine waves in all environments and applications, is false.

Oh yeah? We'll get busy rewriting all the text books.

 

[tmtomh]

It is argued that once a digital pulse or square wave enters a conductor, it becomes analogue because it no longer is a perfect square wave (or pulse).

This entire subject is always based on an original fallacy: "once a digital pulse or square wave enters a conductor, it becomes analogue." (To be clear, I am NOT blaming you for this fallacy.)

This is simply untrue - or at the very least is such a meaningless claim in this context that it is misleading and therefore functionally equivalent to an untruth. A digital signal in a conductor is not analogue - it is electrical, and there's a huge and important difference between analogue and electrical. If the signal became analogue in a conductor, then the specific shape, amplitude, and timing of the signal (pulses, square wave, whatever) would have a specific, ANALOGOUS impact on the sound - that's what analogue means.

But this is not what happens: the signal still contains digital information, not analogue information. Whatever is on the receiving end makes a digital aka binary interpretation/conversion of what it receives, NOT an analogue interpretation/conversion. The signal is subjected to binary thresholds, not analogue reproduction.

Digital does not become analogue until it get into the analogue stage of a DAC.

I think the confusion here stems from the place where a lot of audio confusion stems from: folks applying intuitive ideas where they don't apply. Some folks seem to think that digital = electronic and abstract, while analogue = electrical, physical, and mechanical. That's a false distinction based on a series of conflations.

 

[DonH56]

I do understand Fourier analysis, and that mathematically a square wave can be broken down to a series of sine waves, but that blanket, mathematical definition does not apply to a car indicator system. Hence why I used it.

If you analyze the voltage across or current through the car indicator then you can apply Fourier analysis to it and see the individual frequency components ("sine waves") that comprise (make up) the waveform. Car indicators, switches and lights, still obey the laws of physics, Maxwell's Equations, and all that jazz. A very similar system, a simple switch and a voltage source, is used in introductory electrical engineering and physics courses to relate transient and steady-state analysis, teaching Fourier and Laplace transforms, and other equations that describe a system. You can carry the equations through to the optical domain if you wish; that same analysis is used for TOSLINK, VCSEL, and long-range optical links as well as car indicator lights. Or the RF domain if you want to carry it to electromagnetics and wave theory. Fourier analysis is a pretty fundamental tool.

You can describe a square wave, or your car indicator, in the time domain or the frequency domain as you please, without relation to how it is created in practice. Just different ways to describe the same waveform.

With respect and thanx to all who replied.

Uh, yeah, right...

 

[pablolie]

...
I am arguing that the notion that square waves do not exist in the real world, and all are composed of sine waves in all environments and applications, is false.

To pick this one up: I am arguing that it couldn't matter less when it comes to the discussion of digital audio. Whether the lowest signal impulses are bumps or squares or two-squirrels-banging-in-a-box couldn't matter less as long as they are within spec... and these days you get all the application notes in the world to make sure your system is up to spec. So the "true nature" of the signal path is completely abstracted. Photons? Waves? Who cares. It works.

I do understand Fourier analysis, and that mathematically a square wave can be broken down to a series of sine waves, but that blanket, mathematical definition does not apply to a car indicator system. Hence why I used it.

I have no idea why you think a Fourier transformation doesn't apply to a car indicator system. Of course it does. What we don't need is a transformation where the N is to infinity, a much rawer approach suffices for such basic on-off stuff. We most certainly don't need a clean square wave for basic on-off stuff. We can get away with an extremely dirty signal source. Whether you want that embedded in your audio system is up to you.

With respect and thanx to all who replied.

Same here, I am not being facetious at all, nor attacking you.

I think the problem with this topic is that ultimately the audiophile "digital-vs-analog tech" discussion has little to do with either. The truth is that all audio systems these days are hybrid constructs. You can implement your system end to end with tubes and tape and vinyl and guess what... most of your music was recorded in digital, several elements in the power supplies and inner circuits *will* contain solid state transistors (which by definition somewhere-somehow is based on on-off binary logic), etc. Or - as a digital fan, the "A" part in your DAC will always have a far more influential part in the sound of your system than the D does.

A lot of the discussion in this topic seems to be about twisting "scientific truth" into a strawman argument for the SQ merits of whatever people define as "digital" or "analog". The discussions about perfect squares and their nature has *zero* to do with how "digital" audio works... whatever you mean with digital. The encoding of music? The amplification system? The power supply?

All of us have hybrid digital-analog systems these days, for many reasons.

 

[pkane]

If you analyze the voltage across or current through the car indicator then you can apply Fourier analysis to it and see the individual frequency components ("sine waves") that comprise (make up) the waveform. Car indicators, switches and lights, still obey the laws of physics, Maxwell's Equations, and all that jazz. A very similar system, a simple switch and a voltage source, is used in introductory electrical engineering and physics courses to relate transient and steady-state analysis, teaching Fourier and Laplace transforms, and other equations that describe a system. You can carry the equations through to the optical domain if you wish; that same analysis is used for TOSLINK, VCSEL, and long-range optical links as well as car indicator lights. Or the RF domain if you want to carry it to electromagnetics and wave theory. Fourier analysis is a pretty fundamental tool.

You can describe a square wave, or your car indicator, in the time domain or the frequency domain as you please, without relation to how it is created in practice. Just different ways to describe the same waveform.


Uh, yeah, right...

Fourier transform applies to every single real-world signal that has ever existed since the beginning of the universe. Yet, somehow it doesn't apply to the car indicator system Science books will definitely need to be rewritten!

 

[amirm]

Now if you put that square wave into an analyser, you will see that it is not perfect and detect sine wave components, but who cares?

You should care because it explains things that you cannot possibly intuit without it. I show an example of that right at the beginning of my video on square waves:

There are more examples starting around 8:00 minute mark.

 

[oleg87]

I am arguing that within hifi (not telecom, not TV transmission, not ultra high data rate, not ....) digital audio transmission through a conductor, with in short distances (remember Hifi environment ) the pulses, the square waves are, indeed square!

Unless this is some kind of magical hifi system made out of ideal voltage/current sources and no capacitance or inductance, they most certainly are not.

 

[Ken Tajalli]

You should care because it explains things that you cannot possibly intuit without it. I show an example of that right at the beginning of my video on square waves:
There are more examples starting around 8:00 minute mark.

Thank you for your reply.
For clarity, that statement I made, was in regard to a car indicator system, and within that application only.
Otherwise, I have already said everything I wanted to say.
I read from now on.

 

[Plcamp]

How about like this:

View attachment 247362

BTW, many people here on this very thread, have stuck to their guns, I suppose that qualifies them for being wrong.

For me, that is obviously the exactly correct way to look at everything.

Which doesn’t change the fact that the Fourier view is simply the view of a waveform with the x-axis changed from time to frequency.

 

[Ken Tajalli]

For me, that is obviously the exactly correct way to look at everything.
Which doesn’t change the fact that the Fourier view is simply the view of a waveform with the x-axis changed from time to frequency.

Actually, Monsieur Fourier looked at things like this:

Composed, calm, . . . Which is far less shifty than yours!
I suppose when one is in the court of crimson king, one needs to have their wits about them!
That should explain your schizoid look.

BTW I am still amazed by that Michelson's device, just WOW.

 

[VonGoethe]

Just to make clear what the frequency spectrum of 100baseTX looks like:

 

[pablolie]

Just to make clear what the frequency spectrum of 100baseTX looks like:

Which has nothing to do with the payload integrity or sound quality of the audio bits transmitted... just saying. The PHY layer is simply defined to be good enough to transport stuff reliably and is totally decoupled from the layers above.

 

[DonR]

Just to make clear what the frequency spectrum of 100baseTX looks like:

That null at 125MHz is going to really harsh those highs. Maybe you need some EQ.

 

[Ken Tajalli]

Which has nothing to do with the payload integrity or sound quality of the audio bits transmitted... just saying. The PHY layer is simply defined to be good enough to transport stuff reliably and is totally decoupled from the layers above.

Yep.

 

[VonGoethe]

Which has nothing to do with the payload integrity or sound quality of the audio bits transmitted... just saying. The PHY layer is simply defined to be good enough to transport stuff reliably and is totally decoupled from the layers above.

Haven't said anything about that this has something to do with sound differences.

If one would deal a little bit more intensively with the matter, then one would know that apart from the differential signal also common mode interferences are transmitted via Ethernet. The galvanic isolation is only effective in the very low frequency range.
I have already made many measurements here and know what I am talking about. These common mode interferences get into the ground system of the receiver and are also passed on by the streamer via the USB ground to the DAC.

It is not only zeros and ones that are transmitted.