• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

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

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
Uhmm we are still talking about home usage of relatively short interlinks and whether or not one can use coax instead of 'regular' coax-type cable ?
Not professional (balanced) audio with very long runs and multicable running along stage lighting cables.
Also not about anything well above 100kHz or even 1MHz.
Not talking about microphone cables either... just line level interlinks with RCA connectors.

Yes, twisted cable is a way of shielding for magnetic fields, yes twisted quad configs are also better.
Balanced is better when screened, yes some cheap interlinks may not even have a screen.

I would suggest that using decent (supple) coax will work fine for DC to 10MHz and not worse than 'normal' interlinks.

That's what the thread is supposed to be about. Not dickwaving.
 
Last edited:

Wombat

Master Contributor
Joined
Nov 5, 2017
Messages
6,722
Likes
6,459
Location
Australia
Very true. Maybe because, instead of opening new topics, same questions are being asked over and over again.

Limit thread replies to 50 posts. After all there is very little in audio that can't be worked out via internet searches. :facepalm:

Opening question: Have you looked for an answer before posting?
 
Last edited:

KSTR

Major Contributor
Joined
Sep 6, 2018
Messages
2,690
Likes
6,013
Location
Berlin, Germany
Any coax is a most excellent choice for unbalanced audio interconnect regardless of type, provided it has
- high coverage and continuity of the shield (spiral wire "shields" need not apply) to provide good electrostatic shielding
- high conductivity of the shield to reduce I*R error voltage drops from balancing currents between gear
- true concentric construction with stable geometry which yields very good cancelling of (far-field, homogenous) magnetic fields, similar if not better than wisted pair.

In both regards most any 50 or 75 Ohm rated RF coaxial cable with a braided shield (with ot without additional foil screen) is better that standard audio cables which often are of the spiral shield type that allows for a higly flexible cable.
 

rwortman

Addicted to Fun and Learning
Forum Donor
Joined
Jan 29, 2019
Messages
740
Likes
683
A quick survey of the market in audiophile interconnect cables should be sufficient evidence that almost any damned thing will work as long as it establishes a low resistance connection.
 

syn08

Senior Member
Joined
Aug 9, 2019
Messages
376
Likes
461
Location
Toronto, Canada
Yes. On another forum somebody organized a test where potatoes, mud and wire coat hangers were used as audio interconnections.

Indistinguishable from $1000 boutique cables.
 

Joachim Herbert

Senior Member
Forum Donor
Joined
Jan 20, 2019
Messages
452
Likes
670
Location
Munich, Germany
BTW I have seen units using BNC but AFAIK BNC is designed for 50 Ohm so that's not a clever choice.

There is BNC for 50 and for 75 Ohm.
 

Joachim Herbert

Senior Member
Forum Donor
Joined
Jan 20, 2019
Messages
452
Likes
670
Location
Munich, Germany
And once again, I was talking about pro audio cables.

Have not seen unbalanced connections in Pro Audio für quite a while. What are you talking about?
 

Joachim Herbert

Senior Member
Forum Donor
Joined
Jan 20, 2019
Messages
452
Likes
670
Location
Munich, Germany
Lots of semi-pro (i.e. low budget) equipment have RCA inputs.

So sub par performance must be expected anyway. Still do not get the point.
 

toshu

Member
Joined
Nov 19, 2019
Messages
13
Likes
6
I just realized that I am using this cable from my Anthem MRX 1120 to my Paradigm Servo 15a subwoofer. My wife my bed my system cross country and reassembled it while I was laid up after breaking my back.

Is this cable appropriate in this set up?
PXL_20210702_192638763.jpg
 

mhardy6647

Grand Contributor
Joined
Dec 12, 2019
Messages
11,212
Likes
24,172
"Semi-pro" is a marketing gimmick - equipment is either pro or it is not. I don't remember seeing RCA in broadcast radio/tv studios.

RCA (i.e., the Radio Corporation of America) was once de rigueur in studios of all kinds.
Today, of course, RCA is just a name.

https://worldradiohistory.com/Archive-Catalogs/Equipment_Catalogs_RCA.htm

Elvis hears himself on an RCA LC-1A monitor.
http://www.scottymoore.net/RCASpkr.html

1625335064594.png


1625335124051.png

1625335136373.png


In the reel to reel tape industry, there was a plethora of machines that straddled pro and consumer markets -- the term "prosumer" was often applied. TEAC/TASCAM had many such decks over the years.
The Technics RS-1500 family of prosumer decks has, in recent years, achieved wide popularity for the revitalized (and terrifyingly expensive) prerecorded tape market.
https://tapeproject.com/
Otari pretty much owned the "prosumer" market at the very end of the analog tape era; I think virtually every US radio station, large or small, had at least one. I know of one small station here in NH that had three of them ;)

DSC_9662 by Mark Hardy, on Flickr
(For the record: I gave away the two on carts and only kept the rack mount one, which was in slightly better condition.)

More on-topic ;) I am sure there are some unbalanced connections in some studios. :)
 
Last edited:

mansr

Major Contributor
Joined
Oct 5, 2018
Messages
4,685
Likes
10,700
Location
Hampshire
I just realized that I am using this cable from my Anthem MRX 1120 to my Paradigm Servo 15a subwoofer. My wife my bed my system cross country and reassembled it while I was laid up after breaking my back.

Is this cable appropriate in this set up?View attachment 138908
Should be fine. I use "video" cables for audio all the time. If anything, they're better than they need to be, video signals having a bandwidth of many megahertz.
 

Audiofire

Addicted to Fun and Learning
Forum Donor
Joined
Feb 8, 2022
Messages
625
Likes
347
Location
Denmark
In your opinion, the Al foil in a coax cable provides shielding against what?
Great, now use one of those texts on EM theory and calculate how effective is a .1mm aluminum foil against low frequency magnetic fields (like mains hum). Hint: zero, zip, nada. Repeat for the high frequencies these cables were designed for and you'll find it is rather effective, at least that's what Faraday says based on the eddy currents effect.

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.
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.

"Aluminum foil is a good conductor and nonmagnetic; therefore, it can reflect almost any exposure to electric waves, thus providing protection against EMR (Ott, 1976; Pratap et al., 2014). Aluminum foil can reflect about 90% of electromagnetic waves at wavelengths of 200nm (nanometers) up to 1μm (micrometer), increasing to about 99% at wavelengths above 1μm, and may weaken more than 80dB (decibels) of EMR at frequencies over 100MHz. The magnetic field will lose about 63% of its energy with a single sheet of aluminum foil (Pratap et al., 2014)."

Source (attached, with peer review):
Rambung, E., P. Kalanjati, V. and Abdurachman, . Aluminum Foil Shield Diminishes the Electromagnetic Radiation of Mobile Phones in the Cerebellum of Adult Male Rats. In Proceedings of Surabaya International Physiology Seminar (SIPS 2017), pages 97-98.


So a single sheet of aluminum foil can attenuate 99% of everything from 0 Hz all the way up to infrared radiation, which has a wavelength of about 1 μm. Shouldn't you have known that for years if you have a PhD in electrical engineering? I think the trick here is that one should avoid placing a huge amount of power cables, or massive transformers, magnets etc. right next to audio cables...

So yeah, your message could easily be interpreted as patronizing.
 

Attachments

  • Aluminum Foil Shield Diminishes the Electromagnetic Radiation of Mobile Phones in the Cerebell...pdf
    187.9 KB · Views: 171
  • Peer Review - Aluminium Foil.pdf
    1.6 MB · Views: 56
Last edited:

Audiofire

Addicted to Fun and Learning
Forum Donor
Joined
Feb 8, 2022
Messages
625
Likes
347
Location
Denmark
"Aluminum foil is a good conductor and nonmagnetic; therefore, it can reflect almost any exposure to electric waves, thus providing protection against EMR (Ott, 1976; Pratap et al., 2014). Aluminum foil can reflect about 90% of electromagnetic waves at wavelengths of 200nm (nanometers) up to 1μm (micrometer), increasing to about 99% at wavelengths above 1μm, and may weaken more than 80dB (decibels) of EMR at frequencies over 100MHz. The magnetic field will lose about 63% of its energy with a single sheet of aluminum foil (Pratap et al., 2014)."

Source (attached, with peer review):
Rambung, E., P. Kalanjati, V. and Abdurachman, . Aluminum Foil Shield Diminishes the Electromagnetic Radiation of Mobile Phones in the Cerebellum of Adult Male Rats. In Proceedings of Surabaya International Physiology Seminar (SIPS 2017), pages 97-98.


So a single sheet of aluminum foil can attenuate 99% of everything from 0 Hz all the way up to infrared radiation, which has a wavelength of about 1 μm. Shouldn't you have known that for years if you have a PhD in electrical engineering? I think the trick here is that one should avoid placing a huge amount of power cables, or massive transformers, magnets etc. right next to audio cables...

So yeah, your message could easily be interpreted as patronizing.
The references in the quote are:
Ott H, 1976. Noise Reduction Techniques in Electronic Systems. United States: Wiley Interscience.
Pratap S, Khatri J, Jain P, dan Banga D, 2014. Electromagnetic Stress – A Danger to Human Health. International Journal of Emerging Technologies in Computational and Applied Sciences. 14(832): 305-309.

Source:

The following seems to be an old draft of the document and the quote is a little different with an additional source:
Cheung, C. S., 2009. ‘Shielding Effectiveness of Superalloy, Aluminum, and Mumetal Shielding Tapes’. Sunnyvale, California. The Faculty of California Polytechnic State University at San Luis Obispo.

"Aluminium foil (AF) is a mild, thin and low-cost conductor material that can be considered to be a shield against electromagnetic wave radiation (Pratap et al., 2014). The effectiveness of the shield is determined by the amount of reflection loss, absorption loss, and internal reflection loss proportional to the high electrical conductivity and low magnet permeability (Cheung, 2009). AF has an electrical conductivity of 0.63 S/m and a magnet permeability of 1 H/m (Cheung, 2009). The effectiveness of AF against electromagnetic wave radiation is still not known"

Source:

I certainly don't have a PhD in electrical engineering. I am just interested in "some reading about the differences between RF shielding and magnetic shielding". The new document does confirm that magnetic shielding of aluminum foil only becomes really effective at 100 kHz and above, so the message from our PhD user is not necessarily patronizing and could merely be interpreted as such. And here is a relevant quote from the new source:

"In terms of magnetic field, Faraday’s principle does not apply, for magnetic charges do not exist. Nevertheless, magnetic material with high permeability ( µ >> 1) and of ample thickness can create magnetic field attenuation by means of forming a low-reluctance path that draws the material’s magnetic field. On the other hand, thin conductive materials with low permeability also have the capability to provide shielding effectiveness for magnetic field. The shield made of the material will form an alternating magnetic field that generates eddy current on the shield to provide shielding effectiveness. Eddy currents produce this alternating magnetic field of opposing orientation inside the shield. As a result, as frequency increase, shielding effectiveness will increase proportionally as well.

"In cases in which reflection loss is low, metals with higher permeability and increased thickness can be utilized in order to amplify shielding effectiveness.

"In the magnetic field, the impedance of the shield and the impedance of the field are close to equilibrium at low frequencies. This produces a minimum reflection loss. As frequency increases, so does reflection loss in the magnetic field. Thus, reflection loss is nearly directly proportional to frequency.

"In the electric field, the opposite is true; the higher the frequency, the closer the impedances of the shield and the field are to equilibrium, and the smaller reflection loss becomes. Hence, reflection loss is nearly inversely proportional to frequency in the electric field.

"The shielding effectiveness of superalloy, aluminum, and mumetal shielding tapes satisfies the 40 dB shielding requirement as specified in the EMC Specifications of Military Standard Handbook 419A depending on the frequency and the SGEMP fields."

Source:

So the cable must be designed and constructed for a specific characteristic impedance, and the connectors are designed to match that impedance over the desired bandwidth. BNC connectors for 75-ohm applications are designed slightly differently than the normal (50-ohm) versions, true. And as you go up in frequency connectors become more critical as cavity resonances in the connector itself start to cause problems.
But the characteristic impedance of both the cable and the connectors does not matter at audible frequencies, and a cable that is less than a few kilometers/miles long from what I understand. I can even use no connectors at all and solder the conductors in unbalanced interconnects directly to the circuit. Am I right?

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?
I found a flexible 75 ohm video cable with a 24 AWG bare copper conductor in Germany, it's called Cordial CVM 06-37. Perfect for an unbalanced interconnect and the copper braid can be used for the neutral wire. 15 layers of aluminum foil on top of the insulation (terminated at earth reference on one end) should be plenty, which is what the length of a normal 30 cm roll gives (6.1 mm*pi=19.2 mm, 300 mm/19.2 mm=15.6). Fastened and insulated with electrical tape. Don't know, but you could be able to do the same in North America. I believe coax is the best option with this configuration (like Atlas Ailsa Achromatic RCA, just look at the price of that snake oil).

After this, I'm starting to question what is considered "of value" here. Any help would be appreciated.
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.
 
Last edited:

egellings

Major Contributor
Joined
Feb 6, 2020
Messages
4,004
Likes
3,244
75 ohm cable will be okay for audio, as characteristic impedance of a cable does not come into play at such low frequencies as found in analog audio signals.
 
Top Bottom