Author Topic: Cable shielding audiophool or facts?  (Read 5782 times)

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Offline Richard Crowley

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Re: Cable shielding audiophool or facts?
« Reply #25 on: November 15, 2018, 06:30:45 pm »
You are all ignoring the elephant in the room. 



The show-stopping problem with this goofy scheme is that THERE IS NOT RETURN PATH FOR THE AUDIO CIRCUIT.  In an unbalanced circuit, the shield/screen IS the return path for the circuit. If there is no connection between the source shield/screen/return and the destination shield/screen/return, then THERE IS NO CIRCUIT HERE.

Telescoping shield is a long-established way of breaking a ground-loop problem between pieces of professional audio gear.  But IT ONLY WORKS WITH BALANCED CIRCUITS. Because the balanced pair inside the shield is the COMPLETE CIRCUIT which is INDEPENDENT from the shield/screen.



This audiophool scheme takes a perfectly legitimate technique (telescoping shield) and extends it to the absurd point of completely disconnecting the return path by having two disconnected overlapping shields which serves exactly NO useful purpose.

 
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Offline helius

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Re: Cable shielding audiophool or facts?
« Reply #26 on: November 15, 2018, 06:59:27 pm »
To be precise, the return path is through a lossy, low-quality distributed capacitor.
 

Offline Richard Crowley

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Re: Cable shielding audiophool or facts?
« Reply #27 on: November 15, 2018, 07:03:19 pm »
To be precise, the return path is through a lossy, low-quality distributed capacitor.
Right. Which "serves exactly NO useful purpose" at audio frequencies.
 

Online CatalinaWOW

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Re: Cable shielding audiophool or facts?
« Reply #28 on: November 15, 2018, 08:19:50 pm »
If reported correctly there is no return path through the cable.  In my mind the jury is out on that.   Who knows what the cable actually has in it.

The reality is that this will function in a great many systems, since they have a grounded chassis and will get a return through the earth ground.  Makes a joke of the shielding, but what did you expect?
 

Offline vk6zgo

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Re: Cable shielding audiophool or facts?
« Reply #29 on: November 16, 2018, 01:09:00 am »
You are all ignoring the elephant in the room. 



The show-stopping problem with this goofy scheme is that THERE IS NOT RETURN PATH FOR THE AUDIO CIRCUIT.  In an unbalanced circuit, the shield/screen IS the return path for the circuit.
Not necessarily, I have seen plenty of unbalanced circuits which use a pair of conductors & a screen.
But, of course, this doesn't make your comment invalid.
Quote
If there is no connection between the source shield/screen/return and the destination shield/screen/return, then THERE IS NO CIRCUIT HERE.

Telescoping shield is a long-established way of breaking a ground-loop problem between pieces of professional audio gear.
Interestingly, in my experience, it is fairly unusual in Broadcast work, except for low level circuitry like microphones & pickup cartridges for vinyl record replay equipment.
At the higher levels & better S/N ratios of audio reticulated around Studios, it is not necessary.
Quote

But IT ONLY WORKS WITH BALANCED CIRCUITS. Because the balanced pair inside the shield is the COMPLETE CIRCUIT which is INDEPENDENT from the shield/screen.



This audiophool scheme takes a perfectly legitimate technique (telescoping shield) and extends it to the absurd point of completely disconnecting the return path by having two disconnected overlapping shields which serves exactly NO useful purpose.
 

Offline Richard Crowley

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Re: Cable shielding audiophool or facts?
« Reply #30 on: November 16, 2018, 02:51:28 am »
Not necessarily, I have seen plenty of unbalanced circuits which use a pair of conductors & a screen.
But, of course, this doesn't make your comment invalid.
True enough.  But that is NOT the scheme presented by the OP. Else we wouldn't be still discussing this.

Quote
Interestingly, in my experience, it [telescoping shield] is fairly unusual in Broadcast work,
It is rather a common technique.

Refer to the "Bible" of the audio interconnection world, Rane Note 101 "Sound System Interconnection"
https://www.rane.com/note110.html

In Figure 4. Interconnect chart for locating correct cable assemblies...
Note in particular connection diagrams# 1, 2, 5, 6, 7, 8, 11, 12, 13, 14, 17, 18, 23, and 24
More than half of the diagrams show telescoping shield schemes where the shield is connected on one end only.
As you observed, ALL of them feature a second inside wire which provides the return path for the audio circuit.
And the examples here show both balanced AND unbalanced interconnections.

In ALL cases where a single-conductor shielded cable is used, the shield is connected on BOTH ends.
Note in particular, scheme # 20 which is RCA to RCA.



« Last Edit: November 16, 2018, 02:59:21 am by Richard Crowley »
 
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Offline FriedMuleTopic starter

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Re: Cable shielding audiophool or facts?
« Reply #31 on: November 16, 2018, 02:23:37 pm »
What if you made a outer shield (anode) with no connection at all and a inner shield (cathode) only connected to one unit.
In that way, would the outer shield be charged by the RF and EMF from the air and the inner shield would act as the cathode, sinse the charged anode can't discharge
it would get saturated and block for every additional "charge" from the outside?
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Offline Richard Crowley

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Re: Cable shielding audiophool or facts?
« Reply #32 on: November 16, 2018, 04:12:26 pm »
A cable is not a capacitor (except accidentally).
A cable is supposed to CONDUCT a signal from one end to the other.
In order to have a CIRCUIT, there must be a complete path from the source all the way to the destination.
BOTH the inner ("signal") conductor AND the outer ("shield/screen/ground/return") conductor must go all the way through.

Again, I urge you to draw out your proposed scheme and show us the signal path including the return.
Until you do this, you can throw together any number of fantastic words but they mean nothing.

Show us the circuit.  Else this conversation has gone on far longer than it deserved.
 

Online RandallMcRee

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Re: Cable shielding audiophool or facts?
« Reply #33 on: November 16, 2018, 04:13:11 pm »
I think you all are going off on wild-goose chases. You are just speculating about that cable. The OP has not even given us a schematic. This is the beginner's section. The OP (no offense) seems not to have investigated the actual cable in any detail. We should not be disparaging something without evidence and throwing around wild accusations.

That is why my original responses are so brief.

Whenever I have investigated these audiophool cables I have usually found solid engineering mixed with exotic materials: the engineering makes it work and the gold/silver/palladium sells it. But now I am speculating!.




 

Online ebastler

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Re: Cable shielding audiophool or facts?
« Reply #34 on: November 16, 2018, 04:32:39 pm »
Sorry for my bad wording, what I mend was: "I think that audiocable goes to ground via the outside shield that also are used as the negative wire and often connected to the case?"

I think it's clear by now, but just to state it explicitly:

The shielding approach which you proposed in your initial post does not provide a gound connection via the outside shield(s). Because each of the shields is connected on one end only, they obviously do not provide a continuous ground connection between the two devices. Hence, this does not work unless there is another, proper ground connection inside the cable.
 
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Online CatalinaWOW

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Re: Cable shielding audiophool or facts?
« Reply #35 on: November 16, 2018, 05:18:57 pm »
Just remember, the OP is self identified as limited knowledge and is reporting what an audiophool has told him about something he heard is a wonderful technique.  Why would you expect the drawing OP did to have any resemblance to the original cable? 

Take a low information content source and pass it through two low bandwidth channels and then spend a lot of energy debunking the output.  Makes sense to me.
 

Offline coppercone2

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Re: Cable shielding audiophool or facts?
« Reply #36 on: November 16, 2018, 05:27:39 pm »
Ok so is it any different then what people to do to fudge usb grounds?

How electrically similar is this to having two shielded cables going between two boxes but only connected to one box and connected to the other box by a small capacitor?

It kinda sounds like it will resonate. You are linking the grounds through a rudimentary distributed high pass filter. The nondistributed model is cable L and R to set impedance then pass capacitance into a lower impedance since the chassis impedance should be lower then the cable unless its some shady ass glued conductive plastic etc.

But its distributed.

In my opinion it smells like a last ditch bs hack but idk for sure.

By controlling the amount of nesting eg protrusion you set the filter parameter impedance and coupling too.

Not sure why to do this. The energy might go through your ground instead.
« Last Edit: November 16, 2018, 05:39:13 pm by coppercone2 »
 

Offline Richard Crowley

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Re: Cable shielding audiophool or facts?
« Reply #37 on: November 16, 2018, 05:40:43 pm »
Ok so is it any different then what people to do to fudge usb grounds?
USB uses a balanced, differential data signal pair (D+ and D-)
The signal is NOT ground-referenced, so (theoretically) it does not require a ground connection.
This is exactly like balanced-pair audio connections shown in my illustration where the cable is "2-conductor shielded cable"

Quote
How electrically similar is this to having two shielded cables going between two boxes but only connected to one box and connected to the other box by a small capacitor?
That is called "telescoping shield" at least in audio circles.
It is illustrated in the illustration as # 1, 2, 5, 6, 7, 8, 11, 12, 13, 14, 17, 18, 23, and 24
Connecting a small capacitor (active at RF but not audio frequencies) at the unterminated end is also regular practice, especially in conditions where places where RFI is a problem.  (Like broadcast transmitter sites, etc.)

Quote
It kinda sounds like it will resonate. You are linking the grounds through a rudimentary distributed high pass filter
But its distributed.
No, it is not any kind of filter.  Draw out your proposed circuit with the "filter" and show us.
Words mean nothing at this point in the discussion.  It is monumental BS.
 

Offline coppercone2

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Re: Cable shielding audiophool or facts?
« Reply #38 on: November 16, 2018, 05:43:20 pm »
Your shield impedance depends on the capacitance so its a high pass filter with impedance set by l of the lenght if you imagine it as nondistributed.

By shady usb ground i meant when people put like a 5k resistor between usb grounds. This is the same thing but you are putting a freq dep element c rather then r
 

Offline coppercone2

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Re: Cable shielding audiophool or facts?
« Reply #39 on: November 16, 2018, 05:47:02 pm »
Untelescope them in your mind till the overlap is almost nothing and you will see it as two inductors connected by a cap
 

Offline janoc

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Re: Cable shielding audiophool or facts?
« Reply #40 on: November 16, 2018, 06:01:42 pm »
To be precise, the return path is through a lossy, low-quality distributed capacitor.

Nope. At audio frequencies the impedance of such capacitor would be such that it wouldn't have any chances of meaningfully working. The setup would only work if both devices are powered from mains and then the circuit closes through the mains - with all of the wonderful consequences of that, such as hum, noise, distortion, etc.

If even one side of the setup would be a battery powered device (let's say a phone having the cable stuck in its phono jack), you would hear zilch.
 

Offline FriedMuleTopic starter

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Re: Cable shielding audiophool or facts?
« Reply #41 on: November 17, 2018, 12:46:58 am »
I have talked to the audio-addicted and tried to understand what he is talking about.
I am not sure about that but I have made a crude drawing.
« Last Edit: November 17, 2018, 12:51:27 am by FriedMule »
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Offline xavier60

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Re: Cable shielding audiophool or facts?
« Reply #42 on: November 17, 2018, 02:04:53 am »
Ground loops are not a problem if resulting voltage drops do not become an input noise signal.
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Offline vk6zgo

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Re: Cable shielding audiophool or facts?
« Reply #43 on: November 17, 2018, 03:36:44 am »
Not necessarily, I have seen plenty of unbalanced circuits which use a pair of conductors & a screen.
But, of course, this doesn't make your comment invalid.
True enough.  But that is NOT the scheme presented by the OP. Else we wouldn't be still discussing this.

Quote
Interestingly, in my experience, it [telescoping shield] is fairly unusual in Broadcast work,
It is rather a common technique.

Refer to the "Bible" of the audio interconnection world, Rane Note 101 "Sound System Interconnection"
https://www.rane.com/note110.html

In Figure 4. Interconnect chart for locating correct cable assemblies...
Note in particular connection diagrams# 1, 2, 5, 6, 7, 8, 11, 12, 13, 14, 17, 18, 23, and 24
More than half of the diagrams show telescoping shield schemes where the shield is connected on one end only.
As you observed, ALL of them feature a second inside wire which provides the return path for the audio circuit.
And the examples here show both balanced AND unbalanced interconnections.

In ALL cases where a single-conductor shielded cable is used, the shield is connected on BOTH ends.
Note in particular, scheme # 20 which is RCA to RCA.





At least in Oz, Broadcasting organisations are obviously apostate and don't read your "Bible". ;D
Numbers 21  & 22 are the default, with the others used in special circumstances as per my previous post.
 

Offline Richard Crowley

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Re: Cable shielding audiophool or facts?
« Reply #44 on: November 17, 2018, 05:27:46 am »


That drawing shows an explicit send and return loop/circuit for the audio (red & blue wires).
That is very different than what the OP originally showed us.  That is why I kept insisting on a diagram.

That is essentially circuit #6, 12, 17, 18 etc.
But with an extra telescoping shield from the other end.

Quote
Would that have any effect on EMI or RF?
Very doubtful. And certainly not worth the expense/effort .

Just another exhibit in the museum of audiophool hyperbole. 
Take some conventional engineering practice and extend it well into absurdity.
And then, of course, you can charge ridiculous prices to convince people it is some new magical scheme.
Audiophoolery is a cross between cognitive bias and medicine-show snake-oil quackery.

Audiophools have NEVER been able to demonstrate objective evidence of any of their claims.
 
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Offline FriedMuleTopic starter

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Re: Cable shielding audiophool or facts?
« Reply #45 on: November 17, 2018, 10:11:25 am »
I have ever only heart one reason for buying expensive cables that I thought made some sense:

If you have a great looking system and then put some cheap looking wires on, it looks wrong, therefore nice looking cables to make it all look great. It's like a great turkey made of a great cook and then only add mashed potatoes and ketchup, the turkey doesn't taste the same.
« Last Edit: November 17, 2018, 10:15:29 am by FriedMule »
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Offline Gyro

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Re: Cable shielding audiophool or facts?
« Reply #46 on: November 17, 2018, 10:36:44 am »
Iirc, configurations 5/6/11/12 in the above diagrams is where the much maligned and misunderstood 'Directional' audio interconnects came from.

I believe they used twisted pair screened on unbalanced RCA jacks, with the screen connected at the source end only.
« Last Edit: November 17, 2018, 10:38:40 am by Gyro »
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Offline Bud

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Re: Cable shielding audiophool or facts?
« Reply #47 on: November 17, 2018, 02:19:22 pm »
Just a general comment that single or double shield effectiveness of a specific cable you can look up in the cable datasheet. A reputable manufacturer specifies it there.
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Offline FriedMuleTopic starter

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Re: Cable shielding audiophool or facts?
« Reply #48 on: November 17, 2018, 06:00:18 pm »
Bud, no doubt about that, but now we are talking about a high end cable and not something anyone have ever written any data on, except the marketing on there advertisements:-)
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