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Old 30th December 2009, 10:55 AM   #1
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Default why use CAT5 cable?

i was just wondering whilst taking an outing through FR forum, Why is it alot of people seem to use CAT5 cabling?

I mean yes its good copper, probably as thick as necessary, but doesnt stranded copper carry high frquencies better(surface 'skin' effect)?

I tend to use 16-18 gauge mains cord or similar gauge cheap 'speaker' wire, and tend to look for a reasonable gauge and many strands as a prerequisite.

Is it capacitance that makes the difference? and if so, why not just 'unzip' the two halves of the cable.....

Anything i havent thought of that deserves a mention?
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Old 30th December 2009, 11:09 AM   #2
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Fashion. Convenience. Cost.

I use it in my preamp cabling because it's tightly twisted and (if you buy the right kind) well-shielded. For speakers, it's no better and no worse than the equivalent gauge of zipcord. Use what you like and let the fashionistas rail at you about "hooded trebles" or "refulgent midrange."
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Old 30th December 2009, 11:12 AM   #3
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Stranded copper only has better skin effect properties if each strand is insulated from each other (like Litz wire). Otherwise, stranded just acts like solid of just slightly smaller gague.

I can't hear the difference, but a friend I highly respect says there is one and with his proven skills, I have no reason to doubt him.

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Old 30th December 2009, 11:17 AM   #4
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lol fashion sounds about right........

And yes the effect of SA would be greater in Litz wire, but im sure that many strands still have greater SA than a solid conductor, though not as great a difference as the simple numbers would have me believe, since a portion of each strand is touching its neighbour...

Ill just stick with some low C thick gauge cable i think,,,unless i can afford solid silver cable sometime in the future
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Old 30th December 2009, 12:34 PM   #5
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Low cost, fashion (largely caused by some DIY articles from a few years back that were based on dodgy physics) etc.

Skin effect is usually irrelevant at audio frequencies. See Skin Effect Relevance in Speaker Cables — Reviews and News from Audioholics and Skin Effect and cable impedance

As illustrated in the former, AC & DC losses associated with a 10ft length of 12ga zip wire is in the region of 0.18dB at 20KHz. You're more likely to suffer audible HF issues through excessive wire inductance (note: I am not advocating daft hyper-low inductance designs that push capacitance through the roof) than skin effect per se, especially over long runs.
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Old 30th December 2009, 04:15 PM   #6
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Extremely good wire for almost no cost because we can ride on the backs of billions of miles made for the computer industry.

As important as the wire is the dielectric. Plenum grade CAT5 uses teflon.

Particularily with amplifiers with low output impedance, the higher resistance of the skinny wire can knock back the damping factor, which has some positive benefit with some FR speakers.

dave
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Old 30th December 2009, 04:19 PM   #7
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Quote:
Originally Posted by Scottmoose View Post
As illustrated in the former, AC & DC losses associated with a 10ft length of 12ga zip wire is in the region of 0.18dB at 20KHz.
Assumes a perfect voltage amplifier.

Of more importance (likely) than any HF level loss, is any time delay introduced as the human hearing mechanism is more sensitive to this than HF frequency response (and this capability degrades much slower as we age than frequency detection capabilities)

How audiable this is in cable is still hotly debated.

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Old 30th December 2009, 04:47 PM   #8
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Quote:
Assumes a perfect voltage amplifier.
Right, it's the worst case. With a less-than-perfect voltage amplifier, the minuscule loss gets even smaller. And with normal tweeter impedance rise, smaller yet. I ran through those calculations in another thread.
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Old 30th December 2009, 05:36 PM   #9
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Quote:
Originally Posted by planet10 View Post
Assumes a perfect voltage amplifier.
dave
Also assumes a purely resistive load and that skin effect rather than inductance due to geometry is the primary impedance at 20 kHz, both extremely questionable.
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Old 30th December 2009, 05:40 PM   #10
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Quote:
Originally Posted by planet10 View Post
Extremely good wire for almost no cost because we can ride on the backs of billions of miles made for the computer industry.

As important as the wire is the dielectric. Plenum grade CAT5 uses teflon.

Particularily with amplifiers with low output impedance, the higher resistance of the skinny wire can knock back the damping factor, which has some positive benefit with some FR speakers.

dave

I can see that increasing the impedance seen by the speaker maybe a beneift to FR owners(not me unfortunately) just as using small R to increase the Qts of a driver may also be a benefit if used judiciously.#

However, im not all that sure i rate PTFE insulation anyway.....I wouldn't claim to be an expert but in the applications i see it used(namely for insulating electrical generator bearings from circulating AC currents), its non slip behavior is more important, and indeed more consistant than its insulation properties.

More importantly, as low as the capacitance may be, i cant help but think that the closer proximity of adjacent conductors would increase capacitance greatly, when compared to my 0.50/metre speaker cable which the conductors are spaced about 3mm apart.

On the subject of inductance, all have valid points i believe.

Yes no one here has a perfect voltage amp. We have POWER amps. voltage stage, current stage, or a variation of. IMHO the perfect amp is meaningless, higher wire res will increase volts decrease current flow regardless. the net product is less power. END OF. decrease in power, decrease in output amplitude from drivers. fractions of a dB are pretty meaningless too as i question the beliefs of some that they can hear this(noone here has said they can lol)

but back to inductance...sorry.

according to what i know of inductors from winding my own, smaller gauge yields higher L than larger gauge wire; that is for a given coil diameter and length of wire.

Surely then, this would mean that cat5 would in fact be MORE inductively reactive than other larger gauge cabling, particularly if twisted as i know many people advocate. you may as well try coax TV cable IMO, harsh as that may sound...

common mode noise..........lol if low level signal and a balanced system then yes but at speaker levels...questionable. sorry just reading some snake oil peddlers opinions ,,, side tracked again.

The only reason i can see to use Cat5(or 6 etc) would be its price, although i don't think its a lot cheaper than 0.50/metre, unless you're getting 100m or 1km at a time...is it really any better than 'el cheapo boggo' standard twin mains flex? i doubt it. unless you can get the CAT5 free. since i can get plenty of silicone rubber insulated 13amp twin core, For free no less, then i think i may stick to that stuff, unless there is some really good reason for me to use a weak solid core cable, with ultra thin insulation

No offense meant Dave, you speak a lot of sense on here most of the time, and i respect that. I even respect the strange, mad, verging on 'snake oil' support you give to enable; merely as i haven't tried it and cant dispute it, as there is a gnat's wings chance it might well work at least slightly.

However, i cant support the opinion that CAT5 would be beneficial over plain 2 core mains--not at least without real evidence, for the reasons above.
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Last edited by mondogenerator; 30th December 2009 at 05:52 PM.
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