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Author Topic: The old thread was locked this one will not be. Audiophile cable discussion.  (Read 11031 times)

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Offline Church-Audio

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Picking a few nits- I’m no EE, or even very circuit-wise so please correct any of my errors here.

Any analog signal passing device, in this case a piece of cable, which has measurable inductance, capacitance, and impedance will form a filter that determines the bandwidth and frequency response through the device (which are closely related but not identical measures).  A length of cable will have a bandwidth limit, which can be described more precisely as a frequency response measurement, as determined by those charateristics.  It’s interaction with the other devices before and after it forms other filters.

That the bandwidths of those filters are orders of magnitude larger and frequency responses orders of magnitude flatter than what is necessary for essentially completely unaffected analog audio signal transmission in competently designed equipment is a critically important point to make in this thread.  Yet that does not change the fact that these phenomena are real, measureable, and predictable.  That they are measurable to tolerances so far beyond any reasonable influence on human audibility bolsters the argument for scientific objectivity.  It does the argument no good to dismiss those charateristics as non-existant when they are simply inconsequential to the intended application in well designed equipment.

The important points in favor of your position (which I agree with) are that those characteristics are real, measurable, and inconsequential to audio transmission except in the specific cases you mention and in improperly designed and/or implemented equipment.

Would you say that's a correct assement?
Yes and it should be noted amplitude can also be effected by resistance of the cable IE signal loss. We can also get inducted noise that can play around with introducing distortion. But this would only be in an extreme case. IE feedback loop caused by a powerful signal that is the same as the signal present in the cable. This can cause problems in phase of the signal. Again most cables with a quality shield will not have this issue. And in speaker wires we do not have to worry about inducted signals at all obviously. Generally speaking capacitance in relation to the circuits the cable is being connected to can change or alter the frequency response by creating a simple filter. This would happen in the high frequency area not generally in the low frequency area.
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Offline Gutbucket

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No, because you need to know the source impedance to calculate the bandwidth.  Therefore the cable itself cannot have a bandwidth (within reason, say into the GHz range). 

The part I've bolded is one source of my confusion I think.  Doesn't that mean the cable itself is ultimately limited to a GHz range bandwidth that is so wide that it isn't significant for the application ("within reason")?   I'm attempting to drill down to basic principles here, rather than practical audio implementations.

That one needs to know the source impedance to determine bandwidth...  OK, that is determining the characteristics of the filters described by the interaction between the cable and the devices before and after it. I think I get that part.

[partly off-topic aside-]
Can a device have absolutely zero measurable source impedance?  Although I may be mistaken, I think I’ve read about amp designers playing with designs which achieve negative impedance, although not necessarily useful.  If so, wouldn’t that create runaway oscillation? I don’t think that would imply infinite bandwidth however.

Quote
However, when we get to digital/RF signal transmission there is usually a defined impedance, so for those cables (which also have to be designed with matching characteristic impedance) there is a given signal loss per length of cable.  Still not quite a bandwidth because it's dependent upon cable length.

I understand how signal loss is not the same as bandwidth.  Signal measured at two locations can have the same bandwidth but different levels. Conversely they could have the same level but different bandwidths (dependant on how level is measured, it would have to be a narrow bandwidth measure, well within the corner frequency limits of both).  What I don't get is why transmittable frequency range limits that are dependant on cable length (or not) would not be described as ‘bandwidth’.

Thanks for your help in understanding this.
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Offline raymonda

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Mogami advertises their platinum cable as having more frequency extension than any other cable before it. I guess according to what is being expressed here they are selling snake oil.

Offline Church-Audio

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Mogami advertises their platinum cable as having more frequency extension than any other cable before it. I guess according to what is being expressed here they are selling snake oil.
LOL no they are just saying its very low pf per foot in a way that most consumers can understand including idiotphiles.
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Offline Gutbucket

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Thank you very much for those clarifications, Jon.
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