Canare also use a carbon-plastic layer, IIRC. You have to be sure to cut it back.
Just tried my 40yr. old 1/8W carbon comp (1K) at full line level, nothing interesting (certainly no seconds) thirds just above noise maybe. Nothing else at all.
60's what's that supposed to mean? Especially after that AudioXpress article with as much confounding noise and tones issues as possible. We didn't have a differential out low distortion oscillator in 1982 now you can do it with a sound card. Save for a little line incursion I like to see nothing but noise and what I am looking for.
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An imperfect RF cable can be directional because it is a significant fraction of a wavelength. An audio interconnect is not.simon7000 said:
What is full line level? 100 mV, 774.597mV. 1 V?
Send me one.
The whole point is that the bridge reduces the fundamental so you can see the harmonics. 16 bits at 10kHz sampling rate should be enough. Although I would do 64K averages to clean up the noise.
The resistor bridge test with null balancing is a dead simple classic. There are more than a few people now using it.
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Just discovered the term Passive Intermodulation, PIM (not Phase ...). This has been mentioned a couple of times on diyAudio, but then seems to be quickly discarded. Reading the material, it's like meeting an old friend, my head's bobbing in recognition of the symptoms ... people will argue that this is all -150dB down stuff, and only matters for high RF - well, my ears tell me otherwise, I only get the sound that satisfies me when I worry about such things ...
Interestingly, only very expensive, sophisticated testing gear will pick up the degradation caused by this behaviour - now, where have I heard that before ... 😉, 🙄
Interestingly, only very expensive, sophisticated testing gear will pick up the degradation caused by this behaviour - now, where have I heard that before ... 😉, 🙄
Yeah, need to be sure it doesn't contact the center conductor.
By the way, what I meant when I said fancy was the carbon fiber braid, which is a bit more exotic than conductive plastic.
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I have no experimental data. I just have to get by with some understanding of transmission lines. Without understanding, experimental data contains no information.simon7000 said:
It depends on your definition of directionality, but strictly speaking, no: linear networks are reciprocal, and that includes cables.
If you mean some sort of asymetry, that's another story, but it is not actual directionality.
Some understanding of transmission lines should let you know why the theory does not apply to audio interconnects.
At some point in your education you should have learned that even when you are using an applicable theory it still diverges from reality at some point. It is examining those divergences that leads to increased understanding.
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Nothing is perfectly linear. The better your test equipment and method the finer the detail you can observe.
The high frequency approximation used by RF engineers does not apply to audio interconnects, which is not appreciated by some people - many do not even realise that the HF approximation is not the full theory as most undergraduate EEs are not taught it. However, the full theory does apply and leads to the conclusion that audio interconnects are too short for anything complicated to happen. Thus we can use the 'short cable' approximation rather than the RF 'low-loss cable' approximation.simon7000 said:
I agree entirely. That is why in some cases an understanding of the basic physics is better than the approximations often taught to EEs. However, many people on here know less than typical EEs, not more.
But almost everything is sufficiently linear that perturbation theory works fine. That includes cables. For an audio cable to be directional you would have to have some effect which is sensitive to both voltage and current, such as magnetoelectric coupling in the insulator. This would then allow the cable to detect the direction of power flow.
For an RF cable to be 'directional' you simply need a small taper of characteristic impedance from one end to the other, and for the cable to be long enough compared to a wavelength for this to be noticeable.
My experience is that other people around me can pick up the 'good' sound - they may not be able to point precisely to the attributes or characteristics that make it so, but they certainly know that there is a difference, when it's 'off-colour' !
A giveaway is being able to run at high volumes, and no-one comments or complains - the sound doesn't have an artificial, 'look at me!' quality - it sounds "normal", like real life sounds ...
A giveaway is being able to run at high volumes, and no-one comments or complains - the sound doesn't have an artificial, 'look at me!' quality - it sounds "normal", like real life sounds ...
Probably by me.
150db down is close to the limit of a GOOD connector and is hard to measure. I have seen worse than 100dB down. There is no reason why PIM should only apply to RF, speaker cables run at similar currents and nonlinear contact resistance does not care abour frequency
True, but cables, even ordinary ones, are amongst the most linear of components (compared to to capacitors, inductors, even connectors) and at the operating level of a VNA, they are not going to produce anything detectable.
Any observed directionality is likely to be caused by a second order interaction between asymetry (which is easily observable) and some other effect, like impedance mismatch.
When you see such an effect, try to change the output power of the VNA: if it is caused by non-linearities, it will exhibit a strong dependency to power.
If the "directionality" remains the same when you increase or decrease the power by 6dB, it simply means it is a linear artifact
The connectors are never exactly 50R and usually different. So when the cable is more than about 10% of a wavelength long the direction affects the impedance measured. This is not relevant to audio
Yes. The lumped approximation is good enough for audio, unless we are speaking of long telephone lines.
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