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

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#21
Thank you, it's good to know experts like you are available to help cure my ineptitude and ignorance of such electrical things.
You are welcomed :D. I am sure you would also appreciate the information that the skin depth in copper @10KHz is about 0.6mm and @100KHz is 0.2mm :D.

So you still recommend coax cables for audio, right?
 

solderdude

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#22
In typically applications, non-magnetic materials like copper or aluminum have virtually no effect on low-frequency magnetic fields.
 

DonH56

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#23
You are welcomed :D. I am sure you would also appreciate the information that the skin depth in copper @10KHz is about 0.6mm and @100KHz is 0.2mm :D.
Amazingly enough I actually have some understanding of skin depth and even wrote a little article about it and its irrelevance to audio many years ago. I think Amir copied it over here.

So you still recommend coax cables for audio, right?
Yes, to shield from RFI/EMI at higher than audio frequencies, as has always been their purpose. Plus they are convenient. I never said they did anything for low-frequency EM fields. For that matter neither Al nor Cu provide effective magnetic shielding anyway (non-ferrous). For magnetic shielding there are cables with mu-metal and other materials in widespread use.

In any event trolls and insults have taken over ASR, alas. Guess I should be happy to have joined JJ and Floyd in garnering such attacks.
 
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#29
Take a look at the Technical Expert tag by DonH56's username. It does mean something. Then realize when he responds we are getting advice from a knowledgeable person for which we should be happy.
I'm not debating anybody's qualifications, not sure where you got this idea?

Otherwise, for my education, individuals wearing the "Technical Experts" tag on this forum are necessary always right? Good to know for avoiding any future interactions other than pats on their expert shoulders.
 

M00ndancer

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#30
Don knows his shit.
True, and the RG-58 cable in question works fine.
FWIW, before I went balanced all the way, I used cheap coax and good connectors and didn’t have any issues.
I still use cheap homemade RG58 RCA cables w/o issues. It's really interesting that some people don't get it. Almost any crap cable works fine. Audio is not high frequency media like video.
 

solderdude

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#31
They do, if thick enough. His name is Faraday, Michael Faraday.
yes, but is there really a relevant difference in thickness between a copper shield and aluminium shield between audio cables and video cables ?
A difference thick enough to provide magnetic screening ?
We are talking about 'regular' coax type interlinks for audio right ?
Not talking about differences between say screened quad cable and 'normal' audio cable.
Also we are talking about lengths of a few meters max I suppose connecting regular (RCA) and line level audio equipment.

I don't think it is wise to run audio cables near mains cables or other devices that create substantial fields anyway unless they are purpose designed for it.
 
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#32
FWIW, before I went balanced all the way, I used cheap coax and good connectors and didn’t have any issues.
Cheap doesn't mean necessary bad, it's all in the cable construction. I can send you a piece of alleged LMR195 that's the worst audio cable I've ever seen. And once again, I was talking about pro audio cables. For home use, I'm sure every half assed shielded cable would do just fine. Yes, balanced is the ultimate solution.
 

M00ndancer

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Otherwise, for my education, individuals wearing the "Technical Experts" tag on this forum are necessary always right? Good to know for avoiding any future interactions other than pats on their expert shoulders.
Being humble and courteous goes a long way. If you dispute, be polite about it.
 
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#34
I still use cheap homemade RG58 RCA cables w/o issues. It's really interesting that some people don't get it. Almost any crap cable works fine.
Almost true. I tried at home audio interconnections with 3ft. of twisted wire (single ended) and found no differences to shielded cable. Incidentally, a pair of twisted wiress are more immune to stray magnetic fields than a regular coax, Mr. Maxwell knows why.
 

SIY

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#35
Cheap doesn't mean necessary bad, it's all in the cable construction. I can send you a piece of alleged LMR195 that's the worst audio cable I've ever seen. And once again, I was talking about pro audio cables. For home use, I'm sure every half assed shielded cable would do just fine. Yes, balanced is the ultimate solution.
Worst I ever used was a high end teflon and silver combo. Remarkably triboelectric.

Pro use is pretty much 100% balanced. I use low noise mike cable for that.
 
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#37
Worst I ever used was a high end teflon and silver combo. Remarkably triboelectric.

Pro use is pretty much 100% balanced. I use low noise mike cable for that.
Don't tell me about teflon in audio, triboelectricity, capacitors changing value when finger pressed, PCBs that peel at the first soldering, etc... Keep it for JC :D.

Not always, but even the balanced cables are heavily shielded, nowhere near coax. I'll take a picture of some samples that I have.
 
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#38
An aluminum foil shield would be better for interference above 50 MHz.
A braided copper shield would be better for interference below 1 MHz.
A braided copper shield would also be better for Common Impedance Coupling noise.
So in most cases a braided copper shield would be better for a RCA analog audio interconnect.
 
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#39
Amazingly enough I actually have some understanding of skin depth
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. Does this make me an audio forum "Technical Expert"? Nope, and honestly I couldn't care less about such tags.

Now, for those saying that "materials like copper or aluminum have virtually no effect on low-frequency magnetic fields" here's an example. Attached is a photo of my self made precision x1000 low noise (0.35nV/rtHz) JFET based measurement preamp. Guess why it is shielded in half an inch of aluminum? If you don't, the second attachment will clarify it. As you can see, the (input shorted) 60Hz component is at -105dB at the amplifier output. Subtract the 60dB of gain and you'll get an equivalent of 6nV at the input. The third harmonic at 180Hz is easier to shield, since the skin depth goes down with SQRT(f) so the input equivalent is around 1nV.

That's pretty good for a chunk of aluminum, isn't it? BTW, shielding the same in a 1/16" aluminum sheet case provides virtually zero magnetic shielding and the 60Hz harmonics are visible up to 100KHz as an annoying "grass".

Of course, this is an extreme case, definitely not relevant for your home audio setup, but then you'll be surprised how many expensive MC head amps have improper shielding resulting at least in annoying hum.

And another BTW, you will notice at the left side of the shielded enclusure a chunk of blue really good shielded audio cable. It's about 7mm thick and in this case it is terminated with a BNC. Any coax will collect a huge amount (at this scale) of hum through magnetic induction. Not this one. The right side SME terminated cable is RG316 coax, since at the output level any magnetic fields effects can be safely ignored.

P.S. For the sake of completness, I'm attaching the results for a same length (1ft.) piece of (good quality Belken) RG6 cable, terminated in short. I kept the top reference at the same (-105dB) for easy comparison (although the 60Hz component is now off scale). Look at the levels of 60Hz odd harmonics up to the 9th and compare with the previous result for the good audio shielded cable. I can't think of a better proof that coax cable at audio frequencies is far from ideal.
 

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Blumlein 88

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#40
I'm not debating anybody's qualifications, not sure where you got this idea?

Otherwise, for my education, individuals wearing the "Technical Experts" tag on this forum are necessary always right? Good to know for avoiding any future interactions other than pats on their expert shoulders.
Well, I've not seen anything Don posted that was wrong in this thread. Yet you used a tone of informing an uninformed student regarding skin depth. It smacked of being dismissive in the way it was phrased. As have a few other of your posts.

Now you put words into my mouth about assuming Technical Experts are always right. You don't have to do that, but you might want to think twice about replying in short quips as if they were ignorant of basic principles.
 
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