posted
I usually don't take it much into consideration, to be honest, I kind of ignore cables altogether unless I get a bunch of noise... However, I find many braid patterns to be pretty similar when viewed either direction, so I don't imagine their generated fields would differ too much...
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
Since the signals are AC there really isn't a signal flow. Any magnetic fields are going to vary depending on whether the signal is positive or negative. If you install a cable in one direction you will have different fields for the positive and negative, if you install the cable inthe opposite direction you will have the same fields but at opposite voltages.
posted
Although capacitance in a cable may have negligible effect on DC or 60 cycle AC cable circuits used for power or control, it does have affect on higher frequency AC voltages. If current in two parallel conductors is flowing in opposite directions, the magnetic fields would also flow in opposite directions, and a natural repulsion would be created. The degree of repulsion depends on the magnitude of the current.
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[This message has been edited by Eli47 (edited 07-08-2001).]
Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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posted
Eli- What you state is true, yes, but questions abound.
1) The voltage of upper frequencies and the capacitance of wire are REALLLLLLLLLLLY small numbers.. If considered, the current must be even smaller. Therefore, the induced magnetic fields would be scientific notation size small. This small won't have an effect on what I consider to be the important range (less than 50khz) that is noticeable, audible, or particularly measureable.
2) The repulsion is of two physical fields and the conductors themselves would undergo nano-vibrations.. But this force would readily be absorbed by the wire coatings, so what does the actually physical force have to do with anything? It wouldn't even be on a magnetostriction scale.
3) The wire braiding causing controlled magnetic fields would have more effect on the inductance of the circuit than the capacitance, I would hazard to guess. Therefore the wire effects on the signal due to braiding would be due to induction rather than capacitance, right? The capacitance of the conductor itself given length would probably be a magnitude or several higher than the capacitative effects due to braiding.. I think
4) Can we get copper to emit light by passing an alternating signal through it, or simple DC? Which would would emit light at a lower energy cost ? Just wondering
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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posted
I guess it comes down to the question of the directionality of signal flow, in relation to what is termed as "directional cable". On several wires including speaker wire I found arrows pointing in the same direction of the braiding. If manufacturers are getting that picky, it makes one wonder. Shadow you made some good points, which as Kappa mentioned may be well beyond my abilities to answer, but hopefully someone can expand on this.
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Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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posted
The repulsion (or sometimes attraction) is also going to vary due to the frequency being fed through the conductors. Being as how music is made up of many complex combinations of different frequencies and not pure tones, you can forget about calculating the effect. And as Shadow Star said, the voltage of the signal and the capacitance of the wire would be really small at the upper frequencies. As such, wouldn't it make sense to seperate the conductors just enough to overcome their repulsion or attraction rather than weave them together?
I guess one way to see if there is a difference would be to scope a signal before and after it runs though a directional cable in either direction. But I doubt our equipment would be able to measure a difference that small. As such, I don't think my listening equipment (my ears)would be able to pick up a difference not measureable.
Interesting question, someone with a little more knowledge could maybe shed some light here.
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Posts: 490 | From: Fort Frances, Ontario, Canada | Registered: May 1999
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I was just having this discussion with a former installer not too long ago. He told me that some of the directional cables had diodes in line. I myself doubt this because i've disected a couple so called "directional" cables and found no such evidence. Wouldn't a diode only be applicable if the signal was totally DC biased (which I don't this is ever used)?
posted
A music signal is alternating current.. Although the total movement of current is usually around zero after one wave period, the current direction DOES vary by approximately 180^, doesn't it? Therefore, putting a diode in line would probably screw an AC carrying device up pretty good, dontcha think? You might want to go smack your installer dude, phys6
Although, I COULD be missing something.
Eli- Heres my take on cable effects-- The highly sensitive instruments that measure cable properties cannot detect much difference in average length cables. Now, after hooking these cables up to a speaker (which is NOT a precision device when compared to a costly Oscope!) and then listening to them, I can say with certainty that anything considered negligible BEFORE the speaker is certainly negligible AFTER the speaker.. Couple that to hearing loss, room effects and psychoacoustics, and you have some misconceptions that I must consider superfluous.
ShadowStar
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Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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You're correct Shadow Star. A diode restricts, or completely stops the flow of current in one direction. Therefore, you'd only get the positive ( or negative depending on which way the diode was installed) half of the wave.
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Posts: 490 | From: Fort Frances, Ontario, Canada | Registered: May 1999
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You could, and possibly would have a diode in a digital cable like the coaxial digital output of a DVD player being as how a digital signal toggles between 0 and usually 5V and never into a negative voltage. Therefore a cable designed for such use could not be used for an analog audio signal.
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[This message has been edited by Inno (edited 07-20-2001).]
Posts: 490 | From: Fort Frances, Ontario, Canada | Registered: May 1999
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