Fundamental Understanding of Interconnect, Power Cable and Wave Propagation

[mlhm5]

I think your post is confusing to someone not in the market for super high frequency cables i.e. 1GHz and above and certainly irrelevant if not meaningless for those who want information regarding cable use at low frequencies.

You are trying to apply UHF and above transmission line theory at audio frequencies, and that simply cannot be done.

Propagation delay is only important in very frequencies where the wavelength becomes shorter and impedance becomes critical. At 20kHz a 1/4 wavelength is 12,300 feet and figuring a 50% VoP (far less than copper, or aluminum) impedance only becomes important somewhere around 6K feet. On the other hand, in the 50-100MHz broadcast area a 1/4 wavelength is less than 2-5 feet. While the cable used has a higher VoP in the 80% range, impedance becomes important at less than five feet at the frequency of digital broadcast, impedance becomes important over inches.

A low capacitance (21pF/ft - that's 21 trillionths of a farad and inductance is less or equal to that number) /low resistance (18-22AWG braided), low crosstalk coax cable like Canare LV77s or a Belden 1694A has few superiors in any cabling requirement in the low to VHF arena.

 

[Febs]

Quote:

Originally Posted by tourmaline /img/forum/go_quote.gif 1) cause they proved it by experimenting. The harmonics start below 20khz. A sound of 15 khz has harmonics of 30khz wich are abruptly cut off!!! cd versus record: record has more extension in the high region hence the highs sound much more lifelike and real. So, you are missing the extension in the extreem highs. This results in microdetail loss.

Who is "they"? What did they prove? I don't dispute that harmonics exist, but if they are not in the audible range, do they matter?

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2) If you compare cd to ascd, wich can go to 100khz, you'll find that sacd sound much more real and has more extension in the high region then cd. So, aperently, there is quite some info above 20khz that attributes to the total sound reproduced! Instruments sound more livelike, voices more real, the sound flows much easier, also in the extreem highs.

One of my most vivid memories of law school is from my first year torts class. A student gave a very lengthy answer to a question, and our professor listened patiently unless he was done. He then stated, "Very good, very good. However, please answer the question that I asked, rather than the question that you wish I had asked." Your answer may perhaps be a good answer for some question, but it does not answer the question that I asked you.

My question is specifically with regards to CD, where there is a theoretical maximum frequency response of 22.05kHz. The discussion that prompted my question was with respect to high frequency attenuation above 20kHz. How can a cable possibly make an audible difference with respect those frequencies if those frequencies do not exist in the playback medium?

 

[meat01]

Quote:

How can a cable possibly make an audible difference with respect those frequencies if those frequencies do not exist in the playback medium?

I don't think we are talking about audible differences in this thread, just science and measurements

I am not trying to be a jerk, just going by what he posted in his original thread

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THIS IS NOT A GENERAL DISCUSSION OR A DISCUSSION ON MERE OPINIONS. PLEASE REFRAIN FROM POSTING IF YOUR REPLY DOES NOT DEAL DIRECTLY WITH ONE OF THE FOLLOWINGS: Frequency Domain Measurement Techniques, Time Domain Measurement Techniques, Modeling Techniques Simulation Techniques for Interconnect, Structures, Electromagnetic Field Theory, Analysis and Modeling of Power Distribution Networks, Propagation Characteristics on Transmission Lines, Coupling Effects on Interconnects, Guided Waves on Interconnects, Radiation & Interference, Electromagnetic Compatibility, Power/Ground-Noise, Testing & Interconnects, Optical Interconnects THANK YOU ALL

 

[Febs]

Quote:

Originally Posted by meat01 /img/forum/go_quote.gif I don't think we are talking about audible differences in this thread, just science and measurements I am not trying to be a jerk, just going by what he posted in his original thread

Fair enough, but in my defense, I am simply trying to understand tourmaline's assertion that:

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a 0.5 decibel difference is believed to be audible. So cd would provit going higher then 20khz since harmonics go way beyond 20khz wich still contain important audio data!

which, as I understand, was in direct response to naamanf's calculations regarding low-pass filtering caused by capacitance.

 

[naamanf]

I think if the discussion is going to be about audio cables, the frequency ranges disused should be in the realm of human hearing. The fact of the matter is nobody can hear 80khz or 100mhz. So bringing factors that effect cables at those frequency is immaterial. It's like discussing televisions and saying it's important they display ultraviolet and ir light.

 

[meat01]

Hey Chesebert, Honest question:

Are we aloud to discuss how the differences in cable materials and conductivity affects the sound quality or are we just talking about the electrical properties?

 

[clatter]

I'd just like to point out that the equations given all relate to coaxial cable, and not all audio cables are coaxial. A two-core cable would be a different matter.

 

[tourmaline]

Quote:

Originally Posted by naamanf /img/forum/go_quote.gif I think if the discussion is going to be about audio cables, the frequency ranges disused should be in the realm of human hearing. The fact of the matter is nobody can hear 80khz or 100mhz. So bringing factors that effect cables at those frequency is immaterial. It's like discussing televisions and saying it's important they display ultraviolet and ir light.

I wasn't speaking of 100khz as a frequency to be heard it is simply used as a max. frequency for sacd in recording. Since sacd doesn't cut of the frequencies at 20khz, the sound contains harmonics up at least 40khz, wich are to believed people can feel those. That's why all new speakers go beyond 40khz now! That's why sacd sounds better then cd because the harmonics, wich contain micro info of the music(say vibrations of a cello) and can contribute to a better/clearer sound at 20khz or lower. Recordings that go beyond 20khz and contain the full harmonics simply sound better cause they contain the full info of an instrument or voice. Sounds flow easier and sound more lifelike and in case of a record, sound more analog.

So, it helps to have a frequency range as high as 100khz so you're sure no harmonics will be lost, even you suppose not to hear them.

In a cable you want the same thing as frequencies get lost due to physics in the cable itself and you'll loose info, no matter how small, the higher frequency range your cable can transport without too much losses, the better it will sound. The table shows that the sounds of a recording loose info in the frequencies AND will sound softer. So, witha good cable the sounds will sound like it has more volume and with a bad cable you have to cranck up the volume to be able to hear the very soft sounds.

 

[tourmaline]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif Who is "they"? What did they prove? I don't dispute that harmonics exist, but if they are not in the audible range, do they matter? One of my most vivid memories of law school is from my first year torts class. A student gave a very lengthy answer to a question, and our professor listened patiently unless he was done. He then stated, "Very good, very good. However, please answer the question that I asked, rather than the question that you wish I had asked." Your answer may perhaps be a good answer for some question, but it does not answer the question that I asked you. My question is specifically with regards to CD, where there is a theoretical maximum frequency response of 22.05kHz. The discussion that prompted my question was with respect to high frequency attenuation above 20kHz. How can a cable possibly make an audible difference with respect those frequencies if those frequencies do not exist in the playback medium?

this is not lawschool.

and as for harmonics, they do exist in the original recording. So theoretically they can go as high as 22khz. But you say you only hear 20khz...still, the harmonics above 20khz add to the detail, body and sound of a recording. sacd goes way beyond 22khz and sound much better and detailed cause it can playback harmonics up to 40khz without a problem. So, in the harmonics above 22khz there is still info. 40khz is believed to be felt by your body. So, even you can't hear those frequncies at 40khz, they still add to the feel and experience of the sound. Speakers all go to 40khz for the same reason! They sound more lifelike.

I compared cd to sacd and stated that frequencies and harmonics above 22khz do add to the sound and detail.
For cable you want as less frequency loss as possible so it makes sense to make cables efficient beyond 40khz in order not to loose too much info. Frequencies act different in a cable and loose info and get softer! Also, if a cable is more efficient(less frequency loss) you can use longer runs of cable.

Without any exception audio equipment going beyond 20khz to about 40khz is picked out as better sounding then equipment that is limited to 20khz! Be it speakers, headphones, sacd or recordplayers.

 

[chesebert]

Quote:

Originally Posted by meat01 /img/forum/go_quote.gif Hey Chesebert, Honest question: Are we aloud to discuss how the differences in cable materials and conductivity affects the sound quality or are we just talking about the electrical properties?

not sound quality; but rather whether and how materials and conductivity affect superposed waveforms in the audio range both in time and frequency domain.

"Sound Quality" is inherently a subjective requirement and this thread need no subjectivity; Its all about what is 'right' in the most objective sense (equations, modeling, analysis, etc).

 

[chesebert]

Quote:

Originally Posted by clatter /img/forum/go_quote.gif I'd just like to point out that the equations given all relate to coaxial cable, and not all audio cables are coaxial. A two-core cable would be a different matter.

yes you are quite right. two core is governed by another set of lumped element model equations

I figure since coax is the most widely used IC config out there, which only make sense as IC transmit small signals.

 

[chesebert]

Quote:

Originally Posted by naamanf /img/forum/go_quote.gif So bringing factors that effect cables at those frequency is immaterial. It's like discussing televisions and saying it's important they display ultraviolet and ir light.

If those factors have 0 effect on low frequencies (20-20khz) then you are right, but that's hardly the case: those factors have small effects. (I am usually in the group that IC makes a difference but relatively small compare to the other stuff like amp).

I don't think I have effectively addressed power cable beyond the power loss equation. Objectively, I can think of no equation that would model a power cable effectively, and I can toss the lumped element model out of the door. As an EE I am puzzled by the difference power cable makes and I honestly think that we need better modeling to account for the difference I and many other heard. This is the rocky road of science, a discovery of 'new phenomenon' requires a new set of modeling to describe its existence and yet those modeling may challenge the current paradigm: the never-ending tug of war.

 

[Febs]

Tourmaline, in order to keep this thread on topic, I'm not going to respond to your points about subjective sound quality. However, I will address this particular point:

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Originally Posted by tourmaline /img/forum/go_quote.gif tSo, in the harmonics above 22khz there is still info.

If your playback medium is a CD, there is no information above 22.05kHz.

 

[chesebert]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif One of my most vivid memories of law school is from my first year torts class. A student gave a very lengthy answer to a question, and our professor listened patiently unless he was done. He then stated, "Very good, very good. However, please answer the question that I asked, rather than the question that you wish I had asked." Your answer may perhaps be a good answer for some question, but it does not answer the question that I asked you.

That's great! I hope he answered the question asked on the exam. You should see some of the exams people write: just brilliant, but never gotten around to answer the actual question.

Quote:

Originally Posted by Febs /img/forum/go_quote.gif My question is specifically with regards to CD, where there is a theoretical maximum frequency response of 22.05kHz. The discussion that prompted my question was with respect to high frequency attenuation above 20kHz. How can a cable possibly make an audible difference with respect those frequencies if those frequencies do not exist in the playback medium?

This is a very good objective question. Does FR @ >22khz makes a difference in cable when the source has @ max 22.0kHz and no equipment can add additional resolution to the wave. The answer to that question is it depends (I know you love the answer

. The reason is that FR > 22Khz is necessary to make sure that FR @ <= 22.05Khz is not attenuated at all as all low pass filters have attenuation well before the 3db cutoff. So if a cable can preserve 0 attenuation at 22.05 khz, then the cable is good enough.

Now in my previous example, you have to assume that no outside force is applied to the original signal, but that's hardly the case. Many CD player/DAC oversample/upsamples and do stuff to the signal that I don't know about. Now that's generally done to give better more accurate final output since your brick wall filter is much better now, but it could extend interpolation into and beyond 22khz set by the redbook limit and whether a cable can transmit this new signal at above 22khz suddenly becomes important.

 

[tourmaline]

Quote:

Originally Posted by Febs /img/forum/go_quote.gif Tourmaline, in order to keep this thread on topic, I'm not going to respond to your points about subjective sound quality. However, I will address this particular point: If your playback medium is a CD, there is no information above 22.05kHz.

True, i never stated otherwise, i used it for comparisson to sacd but on sacd there is! Hence it sounds much better. Especially for sacd the speakers have gone up to 40khz as well and the quality of IC's have gone up as well to match the quality of sacd!

There is NO subjective sound quality between cd and sacd, sacd IS simply much better.

If you playback cd on aspeaker that can go to 40khz or a sacd on the same speaker you'll hear what you'll missing on cd!