[Voyst]

Hi everyone,
 
I know this subject has already been treated, and I wanted to go with 4pin XLR. But then I thaught, in the 2*3pin XLR configuration there is the "ground" wire connected only at one end which plays the role of a shield and which is not in the 4pin XLR. So I was wondering if the 2*3pin XLR was not better than the 4pin XLR solution because of this shield ?

In fact I am really curious about the real use of this third wire which is supposed to play the role of a shield. It is also recommended in the unbalanced interconnects ...
In this conference of the Rocky Mountain Audio Fest Joe Skubinski who works for JPS Labs says that it doesn't play the role of a shield.
 
So if someone could share his point of vue on the subject I would be grateful.
Thank you. 

 

[nikongod]

The 4-pin XLR has a perfect place to hook up a shield in the shell of the plug. 
Since it is not common to hook up pin 1 on 3pinXLR headphone outputs - grounding to pin1 is the same as not grounding! 
 
The third wire (pin 1) is not supposed to play the role of a shield, it is supposed to send a ground reference from device to device. The shell of the plug is supposed to play the role of the shield. 

 

[Voyst]

Quote:

Since it is not common to hook up pin 1 on 3pinXLR headphone outputs

If you look the schema of the wiring of the balanced Headphone of HeadRoom, there is a third wire connected to pin1. And it is said that it permits to reduce the effect of RF interferences.
 
 
You can also see lots of unbalanced interconnect cable designed with a third wire connected only to one end, which is supposed to play the rôle of a shield against RF. 

So I was wondering about the relevance of this third wire. Because if it really helps to reduce RF interferance, the 2*3pin XLR should be better thant 1*4pin XLR ... ?

 

[nikongod]

Quote:

You can also see lots of unbalanced interconnect cable designed with a third wire connected only to one end, which is supposed to play the rôle of a shield against RF. 

So I was wondering about the relevance of this third wire. Because if it really helps to reduce RF interferance, the 2*3pin XLR should be better thant 1*4pin XLR ... ?

 
A **Wire** does basically nothing to shield against RF. you need a braided metal, or wrapped foil shield to stop RF. At that point, yes, you ground one end. 
 
Are you surprised to hear that I would argue in favor of shielding? I love the idea of shielding cables, even output cables (gasp). The problem is that not everyone hooks up pin 1 on a 3pinXLR when used as a headphone output. The odds of you finding pin 1 hooked up are FAR lower than the odds of you finding the shell of the plug grounded to the chassis. So hook the shield to the shell of the 4-pin plug and be done with it.

 

[jcx]

shielding for headphone output cables isn't usually necessary - it does depend on amplifier EMI rejection quality - EMI intercepted by headphone cables as antenna won't create audible sound in the drivers by themselves
 
since cable stiffness, mechanical microphonics from heavy, stiff cable dragging on clothing, the weight pulling on cups are real audible detractions - and the extra shielding adds both - headphone cables seldom use shielding
 
( I always cringe when I see fat cable to the headphone - not that I don't cringe at any mention of aftermarket/diy headphone re-cables too )
 
( please accept my condolences for having listened to
 
Quote:

this conference of the Rocky Mountain Audio Fest

 
the short sample I could stand seemed like they were being careful not to sound like loons - but their profits, entire industry really does rely on FUD, marketing, mythology much more than engineering, psychoacoustic science )
 
 
any wires connected to the amp electronics can work as antenna to couple external EMI into the circuit where RF energy may be "detected" like a crystal radio and converted to audible signals, noise
 
it is fairly easy for the amp designers to include EMI protection on input and output
 
externally you can add common mode ferrite interference suppressors - helps knowing the EMI "threat" frequencies, some thing about the circuit EMI resistance, I/O impedances
 
http://www.audiosystemsgroup.com/AESPaperFerritesASGWeb.pdf
 
fortunately the "best" place for these is right up against the amp housing/connector so they shouldn't be a problem mechanically
 
 
amp input is usually much more sensitive to EMI and depending on system, power configuration there can also be conducted mode EMI
 
its way more worthwhile treating input, power before headphone cables given the common order of EMI problems in typical audio systems
 
superior EMI rejection for source-amp interconnect could use http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc

 

[cubiboy90]

  shielding for headphone output cables isn't usually necessary - it does depend on amplifier EMI rejection quality - EMI intercepted by headphone cables as antenna won't create audible sound in the drivers by themselves
 
since cable stiffness, mechanical microphonics from heavy, stiff cable dragging on clothing, the weight pulling on cups are real audible detractions - and the extra shielding adds both - headphone cables seldom use shielding
 
( I always cringe when I see fat cable to the headphone - not that I don't cringe at any mention of aftermarket/diy headphone re-cables too )
 
( please accept my condolences for having listened to
 
 
the short sample I could stand seemed like they were being careful not to sound like loons - but their profits, entire industry really does rely on FUD, marketing, mythology much more than engineering, psychoacoustic science )
 
 
any wires connected to the amp electronics can work as antenna to couple external EMI into the circuit where RF energy may be "detected" like a crystal radio and converted to audible signals, noise
 
it is fairly easy for the amp designers to include EMI protection on input and output
 
externally you can add common mode ferrite interference suppressors - helps knowing the EMI "threat" frequencies, some thing about the circuit EMI resistance, I/O impedances
 
http://www.audiosystemsgroup.com/AESPaperFerritesASGWeb.pdf
 
fortunately the "best" place for these is right up against the amp housing/connector so they shouldn't be a problem mechanically
 
 
amp input is usually much more sensitive to EMI and depending on system, power configuration there can also be conducted mode EMI
 
its way more worthwhile treating input, power before headphone cables given the common order of EMI problems in typical audio systems
 
superior EMI rejection for source-amp interconnect could use http://www.neutrik.com/en/xlr/emc-series/nc3mxx-emc

 
Basically to say, the pin 1 is only affected when used for connecting between devices - devices, headphone don't need it ?