As pano said, you can attach. The attach window shows the size limits for various filetypes.
This graph seem familiar??
Cheers, John
ps..it's been entertaining watching this discussion.
ah, pps..what is an ""honors degree in low frequency transmission line theory""?
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Spice simulations
Attached are simulations of three cables. 10m DNM (CI 470) 10m Zip (CI 120) and 10m Isolda (CI 8). The mauve trace is the step input, the red trace is the lumped and the blue trace is the distributed R, L & C.
I will attach the circuit later as this lot fills the allocated attachment size limit.
Attached are simulations of three cables. 10m DNM (CI 470) 10m Zip (CI 120) and 10m Isolda (CI 8). The mauve trace is the step input, the red trace is the lumped and the blue trace is the distributed R, L & C.
I will attach the circuit later as this lot fills the allocated attachment size limit.
Attachments
Indeed.
After that, and in, order to get a lot of fun during all the summer, i propose several deep similar subjects.
-Tubes sound better than transistors.
-Fixing your amplifiers on golden cones makes them better.
-Discrete components sound better than integrated circuits.
-Numeric produce aggressive and cold sound. (Vinyl sound better than cds)
-Class D amps are only good for PA or cars. (they sound cold and cheap).
- Without Classe A, no salvation.
- The "sound" of the components.
To conclude with the best of all:
- Measurements means nothing. Listening is the only way. (And the contrary)
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You said 100-200 reflections, think about it the "action" at the load starts with a 15ns delay all the subsequent steps are 30ns wide.
jneutron
I have phrased that as we do in Oz (uni WA). In UK speak, it is degree Bachelor of Engineering (Hons) top marks possible in the unit Low frequency transmission line theory. I don't know what it is in US speak.
I have phrased that as we do in Oz (uni WA). In UK speak, it is degree Bachelor of Engineering (Hons) top marks possible in the unit Low frequency transmission line theory. I don't know what it is in US speak.
Please, specify the conditions of the test. What amplifier? Scale of the signal (both level and time). Where the signal is taken. Charge characteristics. Lenght, capacitance and ohmic resistance of each cable, Signal with same charge and no cable. And, please, no simulations, but real measurements. Real world, as you says.
And, make my day, the same measure with a loudspeaker as a charge.
[edit]Why one ? Two different loudspeakers is more fun.
And two different amplifiers i will be in heaven.
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The first two do not predict your "slower response" glitch, they look like ringing around the desired level. Low pass them (like any real audio power amp would) and they will tend to look alike.
Please, please somebody send me the schematic of a nice 100W amplifier that makes the blue traces.
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Scott
Thinking about it yes you must be right. I dont recall exactly the time delay but at the time of the experiment the delay was as predicted from the speed of signal propagation. In the intervening time I had forgotten the round trip so I was wrong in my example calculation assumptions but it doesnt change the principle nor what I saw ie the steps in the square wave front edge. Of course you do have to use a fast scope to see the staircase so square wavenplots produced in say mag reviews wouldnt show it. I think it was at least a 100MHz one perhaps even faster.
Need to repeat the experiment to establish the hard facts.
Thinking about it yes you must be right. I dont recall exactly the time delay but at the time of the experiment the delay was as predicted from the speed of signal propagation. In the intervening time I had forgotten the round trip so I was wrong in my example calculation assumptions but it doesnt change the principle nor what I saw ie the steps in the square wave front edge. Of course you do have to use a fast scope to see the staircase so square wavenplots produced in say mag reviews wouldnt show it. I think it was at least a 100MHz one perhaps even faster.
Need to repeat the experiment to establish the hard facts.
Ah...you have mis-interpreted my amusement.
I am enjoying the attempts to discuss elegantly, the issue from both sided of the fence.
Both sides are missing the boat.
You are correct, assuming a prop delay of 15 nSec for the length.
I agree with you. The ringing of the speaker line in that fashion will do nothing that the load can see.
Why was the load put higher than the line??? What a messy model, and not consistent with the actuals..
I believe you meant magenta trace.
Why oh why is it anyone would assume that one needs nanosecond risetimes to have reflections on a two meter cable??
Cheers, John
My question was meant to be: What is low frequency transmission line theory?
Cheers, John
Just what i said. And a quite fast amp to get such slew rates ;-)
Will ask some mosquito friend of mine if he can ear such frequencies. The one who complain about my tweeters.
Measurements of 12m DNM cable (420 ohms)
The first picture is the test setup. It doesn't matter what the source (amplifier) impedance is. Ten ohms was used for convenience to show the reflected signal at the source. The source impedance can be between zero ohms and infinity, and the results at the SPEAKER end are the same.
The second picture shows the slow rise time at the speaker end (as shown by a 100Mhz scope) and the third picture shows the reflection ripples at the speaker. The simulations are theory to show that there is a difference between lumped and distributed and the scope pictures show reality.
Following, on the next post, are scope pictures of impedance matched cable.
The first picture is the test setup. It doesn't matter what the source (amplifier) impedance is. Ten ohms was used for convenience to show the reflected signal at the source. The source impedance can be between zero ohms and infinity, and the results at the SPEAKER end are the same.
The second picture shows the slow rise time at the speaker end (as shown by a 100Mhz scope) and the third picture shows the reflection ripples at the speaker. The simulations are theory to show that there is a difference between lumped and distributed and the scope pictures show reality.
Following, on the next post, are scope pictures of impedance matched cable.
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You would think the first thing you learn in transmission line theory would be when it is applicable.
"In many electric circuits, the length of the wires connecting the components can for the most part be ignored. That is, the voltage on the wire at a given time can be assumed to be the same at all points. However, when the voltage changes in a time interval comparable to the time it takes for the signal to travel down the wire, the length becomes important and the wire must be treated as a transmission line. Stated another way, the length of the wire is important when the signal includes frequency components with corresponding wavelengths comparable to or less than the length of the wire.
A common rule of thumb is that the cable or wire should be treated as a transmission line if the length is greater than 1/10 of the wavelength. At this length the phase delay and the interference of any reflections on the line become important and can lead to unpredictable behavior in systems which have not been carefully designed using transmission line theory."
How many orders of magnitudes is a 10 ft cable carrying 20khz away from this.
"In many electric circuits, the length of the wires connecting the components can for the most part be ignored. That is, the voltage on the wire at a given time can be assumed to be the same at all points. However, when the voltage changes in a time interval comparable to the time it takes for the signal to travel down the wire, the length becomes important and the wire must be treated as a transmission line. Stated another way, the length of the wire is important when the signal includes frequency components with corresponding wavelengths comparable to or less than the length of the wire.
A common rule of thumb is that the cable or wire should be treated as a transmission line if the length is greater than 1/10 of the wavelength. At this length the phase delay and the interference of any reflections on the line become important and can lead to unpredictable behavior in systems which have not been carefully designed using transmission line theory."
How many orders of magnitudes is a 10 ft cable carrying 20khz away from this.
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The theory of the reflexion of electrons on line extremities witch makes you able to build an echo chamber with only 5 meters of cables.
Absolutely correct.
That depends on the line to load ratio.
If the load matches the line on a 10 foot cable, the difference between what the load sees and what the source is trying to transmit, is separated by the propagation velocity times the length. That is all. For a standard coax, that would be about 20 nanoseconds of delay. NOTHING else happens.
If the load is two orders of magnitude lower in impedance than the line, this relationship no longer holds.
This common rule of thumb is based on the assumption that the load impedance is at or near the line impedance.
To attempt to use this simplistic rule of thumb on a grossly mismatched line to load setup is terribly erroneous.
Please learn the material first..your attemps at wit are straining a bit.
Cheers, John
On the speaker point of view, the only interesting thing is Current.
Please answer this question: what will be the level of the current in the moving coil at such a frequency ?
And this one: Can-you apply hundred (or thousend) time this tension at such frequency and show us (via some laser interferometric measure) the cone movement of the fastest tweeter. ?
As long as it stays in the audio frequencies domain. Read and argue the previous, please. Please, learn (or consider) acoustic and mechanic material.
That was the sens of my (i agree ) bad joke.
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