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Using a 75 ohm RCA video cable for as an analog audio cable.

BDWoody

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#41
Yes, I see a lot of humbleness around.
You mean since Thursday at about 9:00 when you first joined, and basically started by telling us all how special you are (even though you hated to do it...), then moved on to just throwing out this generally arrogant and dismissive spew as if you were here to straighten us all out, without really having any idea of who anybody is or what their background may be?

Wow...wonder why?
 

DonH56

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#43
I usually hate doing this, but know that amazingly enough I have a PhD in EE and I think I know a little about Mr. Maxwell and his gang of merry men, together with some other things in solid state physics. Over 100 peer reviewed published papers, academy membership in Europe, teached all over the world. Then I gave up some 30 years ago and entered the corporate world, for no other reason than money, now happily waiting to retire in a few years.
There's no real way to assess the level of expertise of any given poster based on a few posts. Nor any real way to prove it based upon a few lines and an anonymous user name, for that matter; we know each other from our posts and in some cases off-site interactions personal and professional. Audio is not my day job, but we have some real experts in that field who contribute, so automatically assuming ignorance and/or stupidity on the part of other posters is a mistake. Nor am I an EM expert; I am sure I have far less knowledge than you about Maxwell et. al. but I am not completely ignorant as you appear to imply. Nor are others on the forum; there is a wide range of expertise.

Does this make me an audio forum "Technical Expert"? Nope, and honestly I couldn't care less about such tags.
Or civility? Could you, instead of denigrating anyone you consider beneath you, compose some posts explaining the importance of shielding and describe what sort of cables we should be using and why? Instead of just explaining why I am such an idiot compared to you, teach myself and others, share your knowledge? That is what ASR is about.
 

DonH56

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#45
Assuming that RFI/EMI shielding for audio is the only thing that matters is flat wrong. Could be true for home users, but not in general. Let me know if quotes are required.
Never said that. My statement did not say that was the only purpose, and I was a little surprised that was the way you took it in preceding posts. In event, there's no point in continuing with this. "You don't have to put out another's candle to make your own shine brighter." - Bill Adam
 

syn08

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#46
You may want to re-read how this shit show started.

I posted an innocent question about Al foil shielding properties, you replied with quotes to at best high school level material and ended with "This place is hardly worth visiting lately" which translates in "here's another idiot that can't tell his ass from a hole in the ground and is abusing this forum and my patience" and that without having the foggiest idea who you are talking with. I tried to stay calm, but...
 

BDWoody

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#48
Wow, I think I reached the status of MHM (Most Hated Member) in 48 hours. Can I get a tag please :D?

Nevermind...
If that was your goal, then congratulations, but maybe take a deep breath before you just act like a vinegar and water rinse...

This is generally a pretty collegial group...stop acting like you're the visiting dignitary and maybe you'll get a more collegial response. Maybe that's just not your style...

Either way, welcome. Happy to learn if you have something of value to share. Not most hated, just a pretty obnoxious way to start is all...

Cheers.
 

DonH56

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#50
Below is how it started. I thought I posted a reasonable response to an unknown poster of indeterminate knowledge. You ran with that and apparently took it as a personal attack? It was not and I am sorry if you took it that way. I am not sure anyone questioned the technical part of your posts, just the way you treated everyone else like idiots.

I always questioned the shielding properties of some coax cables I've seen, when used for analog audio purposes. A thin foil of aluminum and a rather sparse mesh of wires doesn't really help. Add to this the rigidity of the RG-59, RG-60, or even RG316 coax (making it rather inconvenient to use) and you'll find why I usually don't use or recommend using coax cables for audio. Some brand names could certainly be better than the next no name junkstore grade coax, though.

Just look at the heavy shielding of a pro grade audio cable and you'll understand what I am talking about.
The Al foil provides 100% shielding, something harder to achieve with braided copper (or whatever), so that is a good thing. To achieve similar shielding with braids typically requires dual wraps, two layers wrapped at right (90 degree) angles, so make the coax thicker. You can buy RG-59 variations in a wide variety of types having different flexibility, shielding, etc.

For cables that are frequently flexed, the foil can develop splits and tiny openings, so in those cases (which includes interconnects that are fairly frequently moved and pro audio cables used for live sound) braid (and stranded center conductors) works better for longevity (not necessarily for shielding but the good ones are 98% or better). I have a bunch of mic and instrument cables that use thick but flexible outer layers, braided shields, foamed poly or similar flexible inner dielectric, and stranded center conductors. And some less-flexible but better-shielded patch cables for the rack since they are not usually moved and (rarely) stepped upon. At work we have fairly standard RF cables, some with armor to withstand abuse during handling, and some gorgeous very thick yet very flexible lab standard cables that rival some audiophile cables in expense ($10k~$20k for 1 m). Since it is a noisy environment foil shielding foil shielding is common but with a full braid for reliability. I have seen cheaper cables using foil without, or very little, braid but those are not meant for day-to-day lab use.

Flexibility is a function of many things, including the type, number and thickness of the shielding, type and thickness of the center conductor, type of dielectric (insulation inside), and type and thickness of the external sheath (insulation on the outside plus any additional armor). You can buy RF cables in a huge range of flexibilities from small coax that behaves like a thick floppy string, so a range of standard coax from flexible to very stiff (some cables are armored, i.e. include a semi-flexible plastic or metal protective layer, to guard against abrasion and excessive flexure), to semi-rigid that is basically bendable conduit (metal tubes), to hard coax that is like thick pipes.

BTW coax describes the construction: a center conductor with cylindrical insulation layer and outer cylindrical shield layer, with perhaps an outermost insulating layer for protection. The vast majority of audio interconnects are coax in nature, including pro-grade audio cables, exceptions being the twisted-wire and flat cable some manufacturers sell. Speaker cables are usually twin-lead (zip-cord) cables.

FWIWFM - Don
 

syn08

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#52
Below is how it started. I thought I posted a reasonable response to an unknown poster of indeterminate knowledge. You ran with that and apparently took it as a personal attack? It was not and I am sorry if you took it that way.
No, I took an issue with your statement "The Al foil provides 100% shielding, something harder to achieve with braided copper (or whatever)" which is in general flat, 100%, wrong, in particular in audio. Hence my polite and innocent question trying to clarify what you mean.
 

DonH56

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#53
No, I took an issue with your statement "The Al foil provides 100% shielding, something harder to achieve with braided copper (or whatever)" which is in general flat, 100%, wrong, in particular in audio. Hence my polite and innocent question trying to clarify what you mean.
Not in my world doing mainly RF stuff. Braided copper does not provide adequate shielding unless double-wrapped and sometimes not then as the wraps tend to slip in use. Measured coupling in and leakage out is in general lower with foil (or other "solid") shielding, often much lower. For the lowest-noise measurements and best isolation of GHz signals we use semi-rigid coax. Regular braided coax lets far too much noise through. When using braided coax, typically an additional, isolated shield layer is added to help control signal ground currents independent of the outer shield. That is what a lot of folk call "quad" shielding.

My mistake was immediately thinking of the RF shielding aspects, probably because I was just helping someone dealing with an RFI problem, and not considering other aspects that you pointed out. As for the rest, well, as you said it's there for all to see, and I plan to let this one go.
 

simbloke

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#54
Don't want to patronize you, but if you decide to keep visiting this place, some reading about the differences between RF shielding and magnetic shielding would be in order.
But you did anyway. By suggesting that a member that has made thousands of posts over more than 3 years should reconsider his position now that you are here.
 

syn08

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#55
Not in my world doing mainly RF stuff. Braided copper does not provide adequate shielding unless double-wrapped and sometimes not then as the wraps tend to slip in use. Measured coupling in and leakage out is in general lower with foil (or other "solid") shielding, often much lower. For the lowest-noise measurements and best isolation of GHz signals we use semi-rigid coax. Regular braided coax lets far too much noise through. When using braided coax, typically an additional, isolated shield layer is added to help control signal ground currents independent of the outer shield. That is what a lot of folk call "quad" shielding.

My mistake was immediately thinking of the RF shielding aspects, probably because I was just helping someone dealing with an RFI problem, and not considering other aspects that you pointed out. As for the rest, well, as you said it's there for all to see, and I plan to let this one go.
See? We can 100% agree on a technical side :D. Game over :D.
 

Xulonn

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#56
What an ugly conversation! Reminds me of my first post here - which lead to an even worse reaction than in this thread. It took a while to recover and demonstrate that I was a decent human being, but I managed to pull it off - I think...

(I searched for a humorous meme graphic about pompous fools, but the Google Image search results were too cluttered with pictures of Donald Trump, so I gave up.)

I have known many engineers and scientists with pleasant and engaging personalities who can communicate respectfully with both non-experts and fellow experts. But occasionally, I encounter one who is just the opposite.

In spite of the unpleasantness, I did learn a bit about cables and shielding.
 

Wombat

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#57
RFI/EMI -- radiated signals, like radio frequency interference and electromagnetic interference. Noise.

Not my opinion, see any text on electromagnetics.

This place is hardly worth visiting lately.
I know how you feel. :confused:
 
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restorer-john

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#58
Don't want to patronize you, but if you decide to keep visiting this place, some reading about the differences between RF shielding and magnetic shielding would be in order.
Speaking of reading, I suggest you review some of Don's 2867 posts on this site. A contrite and timely public apology may be forthcoming methinks.
 
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#59
But you did anyway. By suggesting that a member that has made thousands of posts over more than 3 years should reconsider his position now that you are here.
'Apophasis ... To borrow the definition from Chambers, it means "effectively saying something by stating that you will not mention it."
It is a commonly-used word in theology: a description of God is apophatic when He is described using what He is not.'

Perhaps we should be more welcoming of divinities, minor or otherwise, when they announce themselves in our midst.
 
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