Preferred aes/ebu 110 ohm digital cable you have tried

[jap]

That maybe a better option. By the way what brand is your Pandora DAC

Aesthetix

 

[ar-t]

Well, time for me to ruin this thread.................

A lot of the AES/EBU cables that we have measured are NOT 110 ohms. Including some very famous names.

They should try their hand at USB cables.

Over and out.

 

[rockitman]

Mark Levinson MDC-1

 

[bk12]

Well, time for me to ruin this thread.................

A lot of the AES/EBU cables that we have measured are NOT 110 ohms. Including some very famous names.

They should try their hand at USB cables.

Over and out.

Maybe a stupid question...but can you tell me how one can measure the actual impedance of an AES/EBU cable? I am anxious to actually measure the values of mine....

 

[CGabriel]

Maybe a stupid question...but can you tell me how one can measure the actual impedance of an AES/EBU cable? I am anxious to actually measure the values of mine....

The impedance of a terminated cable can be measured with an impedance analyzer. It measures a combined inductance L, capacitance C and resistance R. This is commonly termed LCR.

However, when a cable operates as a "transmission line" the important parameter becomes the "characteristic impedance" of the cable which is different than simple LCR. A cable ONLY operates as a transmission line when the length of the cable is a major fraction of the wavelength of the frequency transmitted over the cable. So it is irrelevant at audio frequencies and only becomes important when the frequency is at least 100Khz to 1Mhz and then only if the cable is exceptionally long. It is important for video signals and high speed data tranmission. It is not relevant when the length of the cable is less than one tenth the wavelength of the transmitted signal.

The best way to determine the characteristic impedance of the specific wire is to look up the specification from the manufacturer. There is no simple or easy method to measure this and it requires long lengths of cable even when you have the necessary test equipment. Characteristic impedance can be determined mathmatically with a simple formula that uses the diameter of the center conductor and the shield and the dielectric constant of the inner insulation material.

 

[ar-t]

Have you ever actually tried that method? Somehow, I doubt it, and/or your results.

Go ahead...............measure a cable at 1 kHz, then try to tell me how it will work as a transmission line. Nope, not buying it.

As for taking the manufacturer's spec'ed capacitance and inductance.................the way they measure it frequently is not the numbers you will get when you use the cable in its intended manner.

Anything other than a TDR measurement is of dubious value.

You can chose to ignore or dispute my stance, but if want to debate, as soon as AT&T "ABAM" cable gets introduced into the fray, the game is over. You are just going to have to trust me on this one. (I doubt you will find anything viable, via Google. We had to bribe someone at SWBT to find out the secret, and why no one could copy it. Hint: 1 kHz capacitance.)

 

[Steve Williams]

Have you ever actually tried that method? Somehow, I doubt it, and/or your results.

That's a pretty bold comment IMHO. Telling Caelin that how he measures a cable is flawed. Wow

 

[BlueFox]

Have you ever actually tried that method? Somehow, I doubt it, and/or your results.

You are just going to have to trust me on this one. (I doubt you will find anything viable, via Google. We had to bribe someone at SWBT to find out the secret, and why no one could copy it. Hint: 1 kHz capacitance.)

There are multiple ways to measure anything, and some are industry standardized. Obviously, to get repeatable, verifiable numbers, the methodology used needs to be public. To say you have measured cables, and few meet some number is one thing, but then say you use a secret method and you can't tell anyone the method is not very confidence inspiring.

 

[ar-t]

Secret method? Seriously?

You guys crack me up. Just because you have never heard of it does not mean it is "secret". (Go tell Agilent, Tektronix, W&G, and several other test equipment vendors their equipment is secret.)

Saying something is industry standardized is akin to saying "We use ISO 9000-whatever". Which only means "We make the same mistake, over and over, and do so with repeated precision."

You can make LCR measurements on a cable, and if you want to believe it, then fine by me. Telling me how that will relate to its properties as a transmission line is total nonsense.

If you want to characterize it as a transmission line, then measure it as a transmission line. Which is what SPDIF and AES/EBU cables are. Using "pretend" audio frequency measurements is why lots of companies can not make a competent cable, for those applications. Add USB to that list, as well.

Show me where I am wrong.

 

[ar-t]

Steve,

Please try to do all of us a favor, and keep the trolls out of this thread. As soon as they show up, I am out of it. If you guys are interested in learning, that is fine. If you want to throw the same mud at us, like you do on every other forum, not going to take it.

Thanks.

 

[Steve Williams]

Steve,

Please try to do all of us a favor, and keep the trolls out of this thread. As soon as they show up, I am out of it. If you guys are interested in learning, that is fine. If you want to throw the same mud at us, like you do on every other forum, not going to take it.

Thanks.

perhaps I am a bit naive but I fail to see where there are trolls here. I do see where several members have made comments about your post, myself included. I found your telling Caelin that his method of measuring is flawed to be somewhat comical TBH. Perhaps you could enlighten us all

 

[ar-t]

He's not here yet; give him time, he will be. At that point, I am out of this thread. Just like every other one he pops up in. Just giving you fair warning, in case I mysteriously vanish. Not ducking anyone. Just tired of the snide remarks, and his quoting us, out-of-context, and incorrectly, on any number of other forums.

Thanks,
Pat

 

[CGabriel]

Hm, well I am not sure that ar-t was talking to me Steve.

I was just answering bk12's question about measuring his cable. I am assuming he is not an expert and I provided a simplified explanation of the difference between LCR and characteristic impedance. Everything that I have provided is straight forward text book stuff. Of course, I am not an expert but do have a fundamental understanding of the issue.

Have you ever actually tried that method? Somehow, I doubt it, and/or your results.

Go ahead...............measure a cable at 1 kHz, then try to tell me how it will work as a transmission line. Nope, not buying it.

As for taking the manufacturer's spec'ed capacitance and inductance.................the way they measure it frequently is not the numbers you will get when you use the cable in its intended manner.

Anything other than a TDR measurement is of dubious value.

You can chose to ignore or dispute my stance, but if want to debate, as soon as AT&T "ABAM" cable gets introduced into the fray, the game is over. You are just going to have to trust me on this one. (I doubt you will find anything viable, via Google. We had to bribe someone at SWBT to find out the secret, and why no one could copy it. Hint: 1 kHz capacitance.)

If you are talking to me, Pat, then you might want to turn the volume down a bit before you blow a fuse.

Tried what method? I didn't recommend a method unless you are talking about using an impedance analyzer to measure LCR. If that is what you are talking about, then yes I have and do use it.

As to manufacturers specifications: If you can't trust the source then don't use their products. As I said, characteristic impedance is easy to calculate if you know the dimensions and dielectric material of the cable. The LCR and characteristic impedance of a cable does not change with application but different measurement techniques and procedures do provide varying results.

TDR measurements are fine for measuring cable reflections and propagation speed but don't provide an accurate measure of characteristic impedance. I have found this article interesting for those that are technically inclined:

http://www.ecadigitallibrary.com/pdf/IWCS05/IWCS0593_ogx.pdf

Pat, I am not disputing your stance because I really don't know what that is other than you are a self-described expert and seem very upset about something. So, if this is a private party carry on with it.

 

[Speedskater]

Measuring a cable at audio frequencies can and has been done for over 100 years (a long distance telephone would not have worked without doing so), but it's not easy. At audio frequencies you can't use the short form radio frequency formula. You have to measure 4 parameters at each frequency of interest and it's a lot of work.

Cyril Bateman measured speaker cables way back in 1996 & 1997.

Jim Brown has an excellent theory paper.
"Transmission Lines at Audio Frequencies, and a Bit of History"
'The behavior of cables at audio frequencies is widely misunderstood'

This tutorial attempts to shed some light and bring some sanity to the discussion.
http://www.audiosystemsgroup.com/TransLines-LowFreq.pdf

 

[ar-t]

As to manufacturers specifications: If you can't trust the source then don't use their products. As I said, characteristic impedance is easy to calculate if you know the dimensions and dielectric material of the cable. The LCR and characteristic impedance of a cable does not change with application but different measurement techniques and procedures do provide varying results.

It doesn't change with application, but look at the catalog of the most popular wire vendor around. They measure the capacitance, of a single twisted pair, that is shielded, with one conductor connected to the shield. So, it is no longer a twisted pair. If you intend to use it, as a twisted pair, then you will get an impedance that is not what the catalog specs. You can take it up with them if you are so inclined. I fought that battle, with their super salesman, over on rec.audio.tech.whateveritwascalled 20 years ago. Your turn.

TDR measurements are fine for measuring cable reflections and propagation speed but don't provide an accurate measure of characteristic impedance. I have found this article interesting for those that are technically inclined:

http://www.ecadigitallibrary.com/pdf/IWCS05/IWCS0593_ogx.pdf

If you think TDRs are not good for that, then you don't get it. I suppose that expense HP TDR we have, where you go through a calibration procedure, so that you can actually read the impedance, directly, without having to do the math, is just an illusion. Thanks for telling me.

Pat, I am not disputing your stance because I really don't know what that is other than you are a self-described expert and seem very upset about something. So, if this is a private party carry on with it.

UPSET? I have measured numerous cables, and a great number of them do not measure the proper impedance. Part of the reason is audio manufacturers view all cables as audio products, and try to apply audio frequency measurements to cables intended to work as transmission lines. May be applicable, at audio frequencies, where they do not act as transmission lines. But at the higher frequencies, those methods fall flat on their face.

Take a cable............any cable................measure its capacitance @ 1 kHz. Do the same @ 100 kHz. Try it @ 1 MHz. Then get back to me.

Better yet, buy a TDR and learn how to use it. You may end up thanking me.

 

[ar-t]

OK, this invite is for anyone. Audiophiles, manufacturers, distributors, or just any interested party.

Send us you digital cable, coax or twisted pair, and we will measure it, and report the results here. I'll go one step further: I'll let a third-party witness the test procedure. If they have some kind of cell phone gizmo, that can take a video, and upload it to "You Boob", for everyone to see, go for it. ("Perry Mason" comes to mind as a local miscreant to act as third-party. He is a lawyer, so there is no way he would lie!)

Only caveat is you have to pay shipping both ways. If your cable measures fine, or it bombs, makes no difference to us. We are not in that segment of the market. You can even obliterate the name, so no one will know its real identity. Fine with me.

Who has the cajones to put their product to the test?

 

[mep]

Exactly what is the test going to prove or disprove?

 

[dallasjustice]

Exactly what is the test going to prove or disprove?

Impedance, I think.
Pat,
I have 2 110 ohm cables I want to bring over. One of them is from a low cost but reputable manufacturer. The other is expensive high end audiophile stuff. I would love to see which one measures closer to 110 ohms. I really don't care which one performs best since I don't use either them anymore.

 

[ar-t]

How to measure cable impedance.................

http://www.home.agilent.com/agilent/editorial.jspx?cc=US&lc=eng&ckey=1000002217:epsg:faq&nid=-536902444.0.00&id=1000002217:epsg:faq

From the article:

Impedance using an LCR meter:

For low frequencies characteristic impedance can be measured by using the so called "open short" method. The open circuit and short circuit impedance is measured on the longest piece of cable that can still be considered a lumped element, usually one tenth of a wavelength. The characteristic impedance is then given by the square root of the product of the two measurements. The drawback of this technique is accuracy. The open circuit and short circuit measurements may be beyond the reasonable accuracy range of the network analyzer. A better method is to measure the open and short circuit impedance using an impedance analyzer that uses a current voltage technique and can therefore measure a wide range of impedance.

So, how long is 1/10th wavelength if you measure at 1 kHz? Do you think it will measure the same if you measure at 1 MHz?

Actually, on most modern VNAs (vector network analyzers), they employ some sort of inverse-FFT, to get time-domain data from the frequency domain ones. One drawback to TDRs is it needs to have a very fast step generator, to get any sort of precision, wrt to distance. (Important if you design RF connectors and/or PCB interfaces for them.) Also gets away from the risk of the step generator destroying a sensitive device. For those reasons, TDRs are not as popular as they were. Still, a lot more useful than any LCR meter, for RF cables.

 

[mep]

Why do you care what an audio cable measures like at 1 MHz? Audio cables aren't designed to be RF cables.