Interesting and instructive story. If there are more "episodes", I'm all ears.
For example, tests that are out by 3 orders of magnitude and the explanations to justify it.
Or, tests which show differences between IC's where there aren't.
You end up chasing your tail.
jn
J.N.
My recount of the events is that there was a statement that coiling a microphone coil changed the sound and this was explained by a change (increase) in inductance.
You stated there is no change in inductance on a twisted pair cable.
I ran measurements that showed a small difference.
You complained that the comparison was invalid because I was not accurately measuring the inductance.
I repeated the test showing the actual inductance and the change. It was very small as previously mentioned and as expected. It was on the order of .5% for a twisted pair and 5% for twisted pair with the shield shorted to one side. (This data was in the image captions. If you hold your mouse over the image the caption appears.)
You now have done your own test, but the graphs you have presented were not of sufficient resolution to show the differences.
The very interesting result was the change in your measurement of resistance. I would expect skin effect to come in around 40-50 kHz for 22 gauge wire. (The wire diameter not really being exact.) Do you have an explanation for this or just an educated guess.
Now the result of wire changing characteristics due to coiling or handling are not exactly unknown. Cat 5 cable (It is a cable not a wire!) has twisted pairs. The improved version adds glue to keep the twists the same. That is because as you coil or bend the wire it stress the twists and adds a bias to the pairs depending on their location in the cable.
I also measured crosstalk between unconnected cables. You seem to believe this is not due to inductive coupling. What do you think causes this effect? (True it is very low, as low as -100 db/100' in some cables.)
Another issue involved is overall cable diameter. Portable microphone cable is often wound with two cord fillers to make the cable rounder. This does tend to increase the distance between adjacent coil wraps.
Of course some cable uses what is called "Star-Quad" where there are four wires twisted and these are then wired with two conductors becoming each side of the twisted pair. This construction provides better noise rejection. The shield stays the same as in other constructions.
Now why a 1000' foot coil of cable would produce poor results with a measurement microphone is interesting. The "Telegraphers Equation" would expect that a 120 ohm source and a 120 ohm load (The cable used has a nominal impedance of 110-120 ohms) should show a flat frequency response but with some uniform attenuation.
The first pass answer would be the microphone source was not 120 ohms but actually lower and the termination impedance was higher. A second issue would be slew rate limiting. At 50 pf/foot there would be 5 nF of capacitance, as the measuring microphone was phantom powered it most likely had a very limited current output. During testing high level signals are used to get adequate S/N ratios. So that seems to be a likely culprit. Now you used a stainless cylinder to test for solenoid effect. If I can find a metal spool I will try that to see what effect there is. Virtually all the wire comes on plastic spools today, so that may be a bit more difficult.
ES
My recount of the events is that there was a statement that coiling a microphone coil changed the sound and this was explained by a change (increase) in inductance.
You stated there is no change in inductance on a twisted pair cable.
I ran measurements that showed a small difference.
You complained that the comparison was invalid because I was not accurately measuring the inductance.
I repeated the test showing the actual inductance and the change. It was very small as previously mentioned and as expected. It was on the order of .5% for a twisted pair and 5% for twisted pair with the shield shorted to one side. (This data was in the image captions. If you hold your mouse over the image the caption appears.)
You now have done your own test, but the graphs you have presented were not of sufficient resolution to show the differences.
The very interesting result was the change in your measurement of resistance. I would expect skin effect to come in around 40-50 kHz for 22 gauge wire. (The wire diameter not really being exact.) Do you have an explanation for this or just an educated guess.
Now the result of wire changing characteristics due to coiling or handling are not exactly unknown. Cat 5 cable (It is a cable not a wire!) has twisted pairs. The improved version adds glue to keep the twists the same. That is because as you coil or bend the wire it stress the twists and adds a bias to the pairs depending on their location in the cable.
I also measured crosstalk between unconnected cables. You seem to believe this is not due to inductive coupling. What do you think causes this effect? (True it is very low, as low as -100 db/100' in some cables.)
Another issue involved is overall cable diameter. Portable microphone cable is often wound with two cord fillers to make the cable rounder. This does tend to increase the distance between adjacent coil wraps.
Of course some cable uses what is called "Star-Quad" where there are four wires twisted and these are then wired with two conductors becoming each side of the twisted pair. This construction provides better noise rejection. The shield stays the same as in other constructions.
Now why a 1000' foot coil of cable would produce poor results with a measurement microphone is interesting. The "Telegraphers Equation" would expect that a 120 ohm source and a 120 ohm load (The cable used has a nominal impedance of 110-120 ohms) should show a flat frequency response but with some uniform attenuation.
The first pass answer would be the microphone source was not 120 ohms but actually lower and the termination impedance was higher. A second issue would be slew rate limiting. At 50 pf/foot there would be 5 nF of capacitance, as the measuring microphone was phantom powered it most likely had a very limited current output. During testing high level signals are used to get adequate S/N ratios. So that seems to be a likely culprit. Now you used a stainless cylinder to test for solenoid effect. If I can find a metal spool I will try that to see what effect there is. Virtually all the wire comes on plastic spools today, so that may be a bit more difficult.
ES
When I measure significant differences in higher order harmonic distortion, consistently, with some cables with virtually nothing, and other cables with a lot, I don't consider the results 'garbage'. SOMETHING is going on, and it is not just some sort of ground loop. Exactly WHAT was creating the distortion was a mystery, and my first attempts to define its source were probably inaccurate, but the distortion was generated by the cable, somewhere. The point is: There was a consistent measurable difference for cables tested at a particular time period. It is true that over the years, it was difficult to exactly duplicate the EXACT results of measurements in the past, but differences still appeared with the same test equipment. I gave up arguing about it, because my measuring target was always changing somewhat, and the attacks that I got from JN and others made it impossible to go any further without improved test equipment, AND with equipment that did not HIDE the distortion.
Indeed it was "something." The problem was that since that "something" didn't comport with preconceptions and desires, you didn't go any farther to fix the experimental issue.
You explained it as an increase due to solenoidal inductive increase, you stated that the equation for a solenoid held, where L was proportional to the number of turns. You also stated this was why you measured 7 millihenries.
I coiled a 50 foot cable, and even when I measured only one conductor, using it exactly like a solenoid, I got nowhere near 7 millihenries. 120 micro.
I stated that there is no inductance increase because the twisted pair net centroid current is zero. You still held to the belief that coiling it increased the inductance as turns squared.
A difference of .5% between two measurements that are one thousand times larger than reality?? Really, you want to stick to that?
And as you later posted in pics, you were certainly NOT measuring accurately. Indeed, a thousand times out of whack is not even measuring.
Historically speaking, I view your data as suspect. You provide no details, no frequencies, no error bands, we've absolutely no idea if you are even measuring inductance. That's how bad your technique has been to date.
Really? You want to go with that as well? My inductance data between coiled and uncoiled is identical to 5 digits, and you're going to go with "not sufficient resolution" on a graph?
Try again.
Sheesh, and I was thinking about normalizing all the data so I could put them on the same graph. Man, you'd have come up with another silly excuse.
It is important to understand what you are looking at, and explain exactly which graph you are speaking of.. I'll explain.
The graph of the twisted pair pin2 to pin 3 does exactly that, but it is primarily proximity effect which is changing the current centroid locations. The inductance begins to change significantly above 100 KHz, as the centroids get closer together. On the solenoidal pin 2 only graph, blue line, note that the resistive increase is suppressed out further because there is less proximity occurring as there is no return conductor twisted to it.[/quote]
Read up on cat5e. They use orthogonal twisting of the 4 pairs to reduce magnetic crosstalk. There is an industry standard specification on the twist pitch tolerance.
Ed, we have no idea what you measured. You provide absolutely no details, no setup, just statements and/or unexplained pics. But the bottom line, is it is NOT solenoidal coupling. You need to lay two cables in a straight line, side by side...and measure coupling vs position where you slide one cable relative to the other. You will find that the coupling changes as a sine function related directly to the twist pitch of the cable. I put that description in my gallery, showing the relationship using a non random spooling of the cable..
I see you've been reading what I already posted. Don't worry, I remember what I wrote.
I use star quad arrangement to minimize loop coupling with 4 conductors twisted and two circuits. If you use star quad with a single circuit, it changes the wire field from that of that of a dipole with external field dropping as 1/R, to a quadrupole field that drops off as 1/R2
Sigh...
Go back and review the telegraphers equation. To wit, look for the prop velocity as a consequence of the per foot resistance and the per foot conductance. The R and G part of the equation. At audio frequencies, the propagation velocity is heavily frequency dependent unless there is a correct balance between RLCG. That is why undersea cables in the old days used mu metal.
I'll ignore the rest of that explanation, as it's moot.
It may be more important for you to make sure you're reading inductance correctly. So far, what I've seen from you hasn't floated my boat. You need a better meter.
If it is applicable to your business, and if you so desire, perhaps a set of very well controlled tests using known samples for reproduceability (sp) could be arranged.
jn
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Really? And you proved tested that how??
Face it John, you got bit chasing your tail. And don't bother with that garbage of "other equipment hides the distortion" schtick..
Yah, that's what a ground loop does. You're the only one mystified. To wit, this:
Questioning abysmally poor testing is not an attack. Nor is trying to teach you what you are doing wrong.
Whoops too late...there's the "equipment hides the distortion goop.
jn
JN
You can take everything out of context as much as you want to. Anyone can go back and read forward. I showed a difference, Demian asked a question about the absolute number and I gave him the inductance. You complained that the relative difference was not absolute, so I repeated the experiment with absolute values.
You said you didn't want to give numbers, then showed a graph. Now even your measurements show changes from coiling.
Now one of my favorite HP quotes taken slightly out of context "The TRUE value has only academic interest."
You can take everything out of context as much as you want to. Anyone can go back and read forward. I showed a difference, Demian asked a question about the absolute number and I gave him the inductance. You complained that the relative difference was not absolute, so I repeated the experiment with absolute values.
You said you didn't want to give numbers, then showed a graph. Now even your measurements show changes from coiling.
Now one of my favorite HP quotes taken slightly out of context "The TRUE value has only academic interest."
The last time you asserted that, I linked to all your posts where you stated what I noted you did. Nice try.
What did you just say??? I complained that the relative difference was not absolute???
Where are you getting this????
I said....your measurements are over a thousand times higher than reality. You have no idea what your meter is telling you.edit: and in case you missed it, your meter was telling you that you were using the wrong settings...well, the instruction book said so as well.
What blubbery. John asked for numbers while I was inputting them into excel, so I busted his chops.
Go back and actually read the posts. Especially your own.
Yah, if you look really close, you can see the red markers JUUUUSt under the green ones. Obviously, accuracy to 5 decimal places isn't enough???
Isn't that what management said about the outside temperature just before the challenger lifted off?
Ed..instead of attacking the problem as a so called "practical engineer", how about attacking the problem as a real one?
jn
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Here ya go ed. This is from wiki.
I've hilited in red the relevant items for you.
Now, with this in mind, think about what happens when a mike cable is coiled heavily upon its self. Think about how each twisted pair can see the shields of the other wraps of cable.
This is what I spoke about when I talked about mu metal and undersea cables. For a while, undersea cables were the largest user of mu metal.
Happy reading.. jn
ps. Sorry the equations don't carry through. Best go to the wiki site.
pps. If you ever have a customer who complains about distortion in a longline twisted pair cable, make sure they didn't put it into metal conduit, or if in a metal ladder tray, make sure it's not snugged up against a partition wall or the tray wall. The proximity can alter the dispersion characteristics of the cable. And trust me, NEC doesn't mention it anywhere in 2005 or 2008 or 2011.
Heaviside condition - Wikipedia, the free encyclopedia
A signal on a transmission line can become distorted even if the line constants, and the resulting transmission function, are all perfectly linear. This happens in two ways: firstly, the attenuation of the line can vary with frequency which results in a change to the shape of a pulse transmitted down the line. Secondly, and usually more problematically, distortion is caused by a frequency dependence on phase velocity of the transmitted signal frequency components. If different frequency components of the signal are transmitted at different velocities the signal becomes "smeared out" in space and time, a form of distortion called dispersion.
This was a major problem on the first transatlantic telegraph cable and led to the theory of the causes of dispersion being investigated first by Lord Kelvin and then by Heaviside who discovered how it could be countered. Dispersion of telegraph pulses, if severe enough, will cause them to overlap with adjacent pulses, causing what is now called intersymbol interference. To prevent intersymbol interference it was necessary to reduce the transmission speed of the transatlantic telegraph cable to the equivalent of 1⁄15 baud. This is an exceptionally slow data transmission rate, even for human operators who had great difficulty operating a morse key that slowly.
For voice circuits (telephone) the frequency response distortion is usually more important than dispersion whereas digital signals are highly susceptible to dispersion distortion. For any kind of analogue image transmission such as video or facsimile both kinds of distortion need to be eliminated.
Derivation[edit]
The transmission function of a transmission line is defined in terms of its input and output voltages when correctly terminated (that is, with no reflections) as
\frac{V_\mathrm{in}}{V_\mathrm{out}} = e^{\gamma x}
where x represents distance from the transmitter in meters and
\gamma = \alpha +j \beta \,
are the secondary line constants, α being the attenuation in nepers per metre and β being the phase change constant in radians per metre. For no distortion, α is required to be constant with angular frequency ω, while β must be proportional to ω. This requirement for proportionality to frequency is due to the relationship between the velocity, v, and phase constant, β being given by,
v = \frac{\omega}{\beta}
and the requirement that phase velocity, v, be constant at all frequencies.
The relationship between the primary and secondary line constants is given by
\gamma^2 = (\alpha +j \beta)^2 = (R+j \omega L)(G + j \omega C)\,
which has to be of the form \scriptstyle (A+j\omega B)^2 in order to meet the distortionless condition. The only way this can be so is if \scriptstyle (R+j \omega L) and \scriptstyle (G + j \omega C) differ by no more than a constant factor. Since both have a real and imaginary part, the real and imaginary parts must independently be related by the same factor, so that;
\frac {R}{G} = \frac {j \omega L}{j \omega C}
and the Heaviside condition is proved.
I've hilited in red the relevant items for you.
Now, with this in mind, think about what happens when a mike cable is coiled heavily upon its self. Think about how each twisted pair can see the shields of the other wraps of cable.
This is what I spoke about when I talked about mu metal and undersea cables. For a while, undersea cables were the largest user of mu metal.
Happy reading.. jn
ps. Sorry the equations don't carry through. Best go to the wiki site.
pps. If you ever have a customer who complains about distortion in a longline twisted pair cable, make sure they didn't put it into metal conduit, or if in a metal ladder tray, make sure it's not snugged up against a partition wall or the tray wall. The proximity can alter the dispersion characteristics of the cable. And trust me, NEC doesn't mention it anywhere in 2005 or 2008 or 2011.
Heaviside condition - Wikipedia, the free encyclopedia
A signal on a transmission line can become distorted even if the line constants, and the resulting transmission function, are all perfectly linear. This happens in two ways: firstly, the attenuation of the line can vary with frequency which results in a change to the shape of a pulse transmitted down the line. Secondly, and usually more problematically, distortion is caused by a frequency dependence on phase velocity of the transmitted signal frequency components. If different frequency components of the signal are transmitted at different velocities the signal becomes "smeared out" in space and time, a form of distortion called dispersion.
This was a major problem on the first transatlantic telegraph cable and led to the theory of the causes of dispersion being investigated first by Lord Kelvin and then by Heaviside who discovered how it could be countered. Dispersion of telegraph pulses, if severe enough, will cause them to overlap with adjacent pulses, causing what is now called intersymbol interference. To prevent intersymbol interference it was necessary to reduce the transmission speed of the transatlantic telegraph cable to the equivalent of 1⁄15 baud. This is an exceptionally slow data transmission rate, even for human operators who had great difficulty operating a morse key that slowly.
For voice circuits (telephone) the frequency response distortion is usually more important than dispersion whereas digital signals are highly susceptible to dispersion distortion. For any kind of analogue image transmission such as video or facsimile both kinds of distortion need to be eliminated.
Derivation[edit]
The transmission function of a transmission line is defined in terms of its input and output voltages when correctly terminated (that is, with no reflections) as
\frac{V_\mathrm{in}}{V_\mathrm{out}} = e^{\gamma x}
where x represents distance from the transmitter in meters and
\gamma = \alpha +j \beta \,
are the secondary line constants, α being the attenuation in nepers per metre and β being the phase change constant in radians per metre. For no distortion, α is required to be constant with angular frequency ω, while β must be proportional to ω. This requirement for proportionality to frequency is due to the relationship between the velocity, v, and phase constant, β being given by,
v = \frac{\omega}{\beta}
and the requirement that phase velocity, v, be constant at all frequencies.
The relationship between the primary and secondary line constants is given by
\gamma^2 = (\alpha +j \beta)^2 = (R+j \omega L)(G + j \omega C)\,
which has to be of the form \scriptstyle (A+j\omega B)^2 in order to meet the distortionless condition. The only way this can be so is if \scriptstyle (R+j \omega L) and \scriptstyle (G + j \omega C) differ by no more than a constant factor. Since both have a real and imaginary part, the real and imaginary parts must independently be related by the same factor, so that;
\frac {R}{G} = \frac {j \omega L}{j \omega C}
and the Heaviside condition is proved.
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Yah, its been what, a year?? As in, Dec 30 2013 to jan 2 2014.
I said I'd measure a red mike cable "next year"...last year. But it had to wait for my lunchtime..
I also busted your chops because you apply a different set of hurdles to your buddies, as opposed to those who do actual engineering for a living.
I'm sick and tired of your "high end audio" schtick, where all engineering is abandoned when it doesn't support a wild A guess.
I've no problem with you and your buddies not understanding physics or engineering concepts discussed here. But making up lies about others isn't going to cut it.
jn
ps. If I didn't think much of you, I'd never have busted your chops. I'd have ignored you.
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