Telos Quantum Active Cable - Snake Oil?

[CG]

1 hour ago, jabbr said:

Too bad that except for differential mode noise (and widespread adoption of balanced cables) none of the above is measured.

 

 

And, balanced cables are in many cases not what people think they are.

 

A twisted pair is a "balanced" cable.  There are definitely positive attributes to twisting wire pairs, especially at the low frequencies of the audio band where shielded cables really don't do the job.  (See various discussions by Henry Ott...)

 

However, to really get the complete benefit package of "balanced" cabling, you also need balanced transmitters and receivers.  Most of these found in audio products lose their goodness for rejecting common mode noise starting right above the audio band.  No matter how much magical thinking or wishing we apply, signals outside the audio band can, and often do, affect performance within the audio band.  So, some qualifiers need to be applied here as well.

 

Despite the comments, this stuff isn't as easy as people want to make it.  Just ask an instrumentation engineer.

[CG]

37 minutes ago, jabbr said:

This is just magic handwaving here :🧛‍♂️

 

Yeah, but...  That's the way people look at things.  Whether made by leprechauns or imbued with quantum effects doesn't matter.  

 

Personally, I am disappointed that well understood engineering and physics principles are not used to describe various products.  Obviously, that's not an effective explanation.  If the marketing didn't work as it does, the companies would either go out of business or take a different approach.  

 

But, hey!  I read through the various comments here on what is labeled as a forum where physics is supposed to rule, and instead I read various statements of "FACT" that probably are true from the perspective of a networking expert, or perhaps a software genius.  They are very simplified and hardly represent the so-called big picture.  (The jitter argument in another thread just amazes me.)  So, just imagine how accountants, musicians, restaurateurs, and various other people who aren't specifically trained in the subject must look at it all.

[CG]

53 minutes ago, jabbr said:

Neutrik vs Switchcraft XLR connectors or ... you know real stuff

 

https://www.rfindustries.com/resources/white-papers/intermodulation-distortion-in-rf-connectors.php

 

https://www.digikey.jp/Web Export/Supplier Content/AmphenolConnex_624/PDF/amphenol-connex-passive-intermodulation-distortion.pdf

 

I'm not saying that the differences in connector sound are specifically due to this - probably not, in fact - but, this just goes to show that low level effects in all electronic components are there whether somebody has a reason to look for them or not.

 

Back in the first half of the 20th century, various mathematicians at the BBC and Bell Labs worked out the effects and relative amplitudes of intermodulation distortion in imperfectly linear communications systems.  At the time, their work was primarily centered around audio, which was their companies' main business, although the math applies elsewhere, too.  Back then, the best they could do was measure harmonic distortion, noise, and some linear effects like amplitude flatness, due to the test equipment available at the time.  

 

Here's the goofy part.  For the most part, we still hang onto those simple tests and the ways they are performed.  Part of it is simple dogma.  Part is to maintain continuity of test results made over the past 70 years.  Part of it, I suspect, is plain stubbornness.  All of this even though the researchers of the day knew that what they could measure was limited.

 

In 2020 it's crazy that we average a zillion samples in order to find distortion products more than 100 dB below the desired tones.  What in the world does that tell us?  Music and other sounds are continuums of samples (in the digital sense) and our ears detect that.  No averaging for 1000 samples.  (For you networking guys in the crowd, ever measure the MER of a digital communications system?  Ever see the displayed constellation explode or collapse briefly?  What's that do to the MER measurement?  ALMOST NOTHING, if you're averaging over a 1000 symbols.  Yet, those symbols are lost or corrupted.  You can see that directly with a BER test.  No wonder that all sorts of error correction schemes are built into the networking standards - they're needed!  What's the implications of that concept in a digital audio system???  What error correction scheme is there between your ears or brain and the network transmission structure?)

 

In addition, unless you're interested in listening to just pure test tones, sound is a combination of a lot of individual tones and their harmonics.  These produce IMD, just as the BBC and Bell Labs guys predicted.   The power in the IMD completely swamps the simple harmonic distortion.  How and where do we consider that?

[CG]

3 hours ago, Arpiben said:

 

Well, PIM Passive Intermodulation distortions can be an issue in RF transmission with co located multi channel transmitters and receivers operating in different power ranges and sharing the same transport media: coaxial cable, waveguide, circulator,antenna.

Transmission power Tx >=+20 dBm  & Receive power sensitivity around Rx = -100 dBm.

But unlike RF, Audio non linearities involved are inband. Therefore PIM should be out of concern for audio cables or connectors.

Despite your introduction warning, in order to avoid confusion it is probably better not to mention it.😉

 

 

Umm, much of the PIM problems with RF fall into the band as well - like the cellular bands.  I'm not sure that's what you meant to say.

 

But, let's use your numbers.

 

You describe a dynamic range of roughly 120 dB.  I'm not sure if the -100 dBm level is the effective noise floor for the receiver or whether that's the minimum receive level for successful operation, and I'm too lazy to look that up this late at night.  So, I'll stick with 120 dB for the moment.

 

Second order distortion goes up by 2 dB for every dB of fundamental power.  Third order by 3 dB, and so on.  Typical audio power levels from a power amplifier are probably between 30 dBm (1 watt for folks reading) and maybe as much as 40 dBm.  At 30 dBm, that would raise the second order IMD level by 20 dB compared to your referenced 20 dBm.  That puts the dynamic range for second order IMD at 100 dB.  It gets worse as you go up in order.  So, maybe it's not so insignificant after all.  Maybe.  Dunno!

 

My point is, this stuff doesn't get measured or evaluated.  It either is blown off as being "obviously insignificant" or dismissed because "nobody can hear that."  Or, worse.  You don't need to search very far to find these kinds of arguments.  

 

That is decidedly different from, "we measured 20 tone IMD and looked at the IMD levels for 31 different kinds of connectors and found that the highest distortion levels were found to be at a level that would be equivalent to 30 dB below a very quiet room's ambient noise level when the audio system is operated at normal listening levels.  The tones were spectrally shaped in amplitude to approach the typical spectral distribution of energy for various forms of music as well as spoken voice.  In addition, a weighting filter was applied to simulate the human aural sensitivity curve.  Finally, out of band signals were also measured to be sure that nothing untoward was found there, in order to be thorough.  The spectra were measured using not only an averaging scheme to minimize the effects of thermal noise in the system, but also using a peak hold function over time so that the relative phase alignment of the test tones and subsequent signal crests of the distortion products were captured as well.  We also found cases where dirty connectors caused much higher levels of distortion that is likely to be audible.  More work is required in that area."

 

One is scientific investigation, while the other is a dorm room argument.  This is the world we live in today.  People need to be persuaded and often the threshold of persuasion is insurmountable based upon forces other than reason.  

 

"Still a man hears what he wants to hear 
"And disregards the rest" - P. Simon, 1968

[CG]

22 hours ago, Arpiben said:

Forgetting RF microwave transmission, as far as I know, in consumer usage nobody is transmitting multi audio channels CS=44/48/88/96/ etc kHz and simultaneously receiving them at the same point with hundreds dB less!

Let's compare apples with apples before providing analogies.

 

Has nothing to do with that.

 

IMD is IMD, whether it's two tones at 10 KHz and 1 KHz (arbitrary choices) or whether it's a channel lineup of complex modulation schemes at microwave frequencies.  The very same mathematics apply, right?  That's comparing apples to apples.

 

The actual question is whether PIM is a condition that exists at lower frequencies such as audio.  And, if so, what levels are these IMD products at the typical power levels used in an audio system.  That's it!

[CG]

1 hour ago, jabbr said:

The real answer is that no real scientist nor engineer cares why you hear a SQ difference when swapping AC power cables to your network switch, yet all the same, if there were a real SQ difference, the difference would be measurable.

 

If they had an idea of what to look for and there was test gear available for looking.  (And, it was funded...)

 

In regard to the cable changes, at a basic level these kinds of questions are based on ideas usually covered in the very first EE course at the college level.  All that mesh and nodal analysis, Norton and Thevenin equivalents, and so on.  That's for direct "hard" coupling between the current loops.  Electromagnetic coupling is covered in an early physics course at the college level.

 

Personally, I would not expect somebody who majored in history, art, accounting, or any of those subjects in college to be familiar with these concepts.  That's not fair.  Same for folks who didn't go to college.  Presumably, people who design electronics systems like home audio would understand these subjects.  If not, why not?

[CG]

26 minutes ago, Arpiben said:

 

Whatever power you are sending your arbitrary tones do you think that you have chance to listen to eventual PIM - 150 dB under ?

Amphenol RF connectors  aren't use in audio applications or frequency range are they?

Just hoping that no audio cable companies will provide any white paper without measurement claiming that they solve PIM issues 😉

 

I don't know.  

 

Are the mechanisms the same at audio as at microwaves?  What is the distortion level at audio?  I don't know.  Maybe you can tell me and everybody else.  If the distortion is at the -120 dB level at 0.1 Watts at microwaves, would it not be greater than -100 dB at audio, assuming things are the same at both frequencies?  An awful lot of Internet forum characters (ink equivalent) are thrown around over DAC distortions at that approximate level.

 

My point is that I haven't seen any measurements or even theoretical analysis.  (Somebody, please point to it!)  There sure is a lot of "That doesn't matter, you idiot a**hole!" type rhetoric, though.

 

Not directed at you, Arpiben, but it sure seems to me that objective thought is awfully selective with regard to audio.