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Balanced XLR interconnect: where to attach the sheild?

post #1 of 10
Thread Starter 

 

I'm building my first set of balanced XLR interconnects and I want to know if I should attached the shield to both ends of the cable?  I saw the cable building schematics on the Rane website where both ends of the shield are connected but I remember reading that some people advocate attaching the shield at the source end only.  I'm a bit unsure as to which approach to take.  I don't want to experiment and try it both ways - I just want to build the cable and be done with it.

 

**Note: I know which pin to connect the shield to, I just want to know if I should connect it at both ends.

 

I tried to find the answer using the search button but I really couldn't find a direct answer.


Edited by skaelin - 11/30/10 at 11:23am
post #2 of 10

well actually, if you are only using this for balanced analogue connection, I would suggest its a better idea to not connect it to a pin (pin 1) at all, but rather to the cable connector shield (at both ends) this way the noise is shunted to the chassis ground of the gear you are connecting, which should be isolated from signal ground (and star ground) by a ground loop breaker. this way it isnt fed into signal ground or even power supply ground. connecting at only one end is for people who dont have their grounding set up correctly and simply creates an aerial and unwanted useless capacitance.

 

now if you plan to use the cables also for AES balanced digital connection, then you should use pin 1 (at both ends) because the reciever looks for the ground reference on pin 1 and will not work without it.

post #3 of 10
Thread Starter 

So are you saying that I should not connect the shield at pin 1 on both ends?

post #4 of 10

 

I use solid core twisted pairs for XLR with NO shield at all.

 

You do not need a shielded cable.

post #5 of 10
Quote:
Originally Posted by ford2 View Post

 

I use solid core twisted pairs for XLR with NO shield at all.

 

You do not need a shielded cable.



that really depends on what the purpose is and as a blanket statement, completely untrue.... if your gear has very good CMRR, the cable run short and the shielding system used too capacitive, then sure often its best with no shield. 

 

 

 

Quote:
So are you saying that I should not connect the shield at pin 1 on both ends?

 

huh?? no I was suggesting to not use pin 1 at all for an analogue balanced cable, but rather to connect at both ends to the connector shield, which isnt a pin at all and should only connect to the chassis. using pin 1 just shunts noise to signal, or power supply ground unnecessarily) both one in the same thing anyway)

 

not all XLRs have this barrel/shield connection, but most do. only use pin 1 (connected at both ends always) if the cable is also to be used for AES/EBU digital cables, because it wont work at all otherwise, but for analogue forget pin 1. NEVER connect only at the source, the only reason that should ever happen is if your gear has badly designed grounding and connecting the 2 components together causes a ground loop, in this case you would be better served sorting out the cause of the grounding issue than pretending its not there and floating the shield at one end


Edited by qusp - 12/1/10 at 4:40am
post #6 of 10
Thread Starter 
Quote:

connect both ends to the connector shield, which isnt a pin at all and should only connect to the chassis. using pin 1 just shunts noise to signal, or power supply ground unnecessarily) both one in the same thing anyway)

 


OK, so I think you are referencing the small rectangular metal tab (pin 4?) extending from the inside of the connector, right?

 

If that's correct, then I should connect both ends of the shield to this small metal tab on each end of the cable, right?

post #7 of 10
Quote:
Originally Posted by qusp View Post



Quote:
Originally Posted by ford2 View Post

 

I use solid core twisted pairs for XLR with NO shield at all.

 

You do not need a shielded cable.



that really depends on what the purpose is and as a blanket statement, completely untrue.... if your gear has very good CMRR, the cable run short and the shielding system used too capacitive, then sure often its best with no shield. 

 

 

 

 


Both You and I know that it was never intended as a blanket statement and only a fool would think such.
 

post #8 of 10

well without knowing the gear in question, it can only be taken as such

post #9 of 10

In general, the shield is connected at only one end.

Which end depends on your gear and the cables usage.

If in doubt, try it both ways and see which way works better.

Whichever unit has the best ground would be the shield

connected end. For example...connect a microphone to

an amp, shield goes at the amp. Connect a battery powered

device to a wall powered device with a three prong cord,

shield goes to the wall powered device.
 

Quote:
Originally Posted by skaelin View Post

 

I'm building my first set of balanced XLR interconnects and I want to know if I should attached the shield to both ends of the cable?  I saw the cable building schematics on the Rane website where both ends of the shield are connected but I remember reading that some people advocate attaching the shield at the source end only.  I'm a bit unsure as to which approach to take.  I don't want to experiment and try it both ways - I just want to build the cable and be done with it.

 

**Note: I know which pin to connect the shield to, I just want to know if I should connect it at both ends.

 

I tried to find the answer using the search button but I really couldn't find a direct answer.

post #10 of 10
Quote:
Originally Posted by Avro_Arrow View Post

In general, the shield is connected at only one end.

Which end depends on your gear and the cables usage.

If in doubt, try it both ways and see which way works better.

Whichever unit has the best ground would be the shield

connected end. For example...connect a microphone to

an amp, shield goes at the amp. Connect a battery powered

device to a wall powered device with a three prong cord,

shield goes to the wall powered device.



sorry mate, but that is the incorrect way of connecting it, you should never connect at one end if you can avoid it, it just turns the cable into an aerial to pick up noise and shunt it back to the source ground, which with proper practices should be connected to the same chassis ground anyway ie NOT signal ground, only reason you might do that is if you have bad grounding practices in the rest of your gear and connecting at both ends causes a ground loop. sometimes studios will do one end for their cables because they need to account for many different manufacturers and not everyone knows what they are doing. given we as DIYers have some degree of control over how our stuff is hooked up and having generally less complex systems are free to do things properly, or at least try to before admitting defeat

 

avoiding pin 1 altogether for ground and instead using the shield connection achieves the same result, but without compromising the shielding. ideally both pin 1 and the connector shield should be connected to chassis/safety ground in the equipment on both sides, but sometimes people incorrectly connect pin 1 to signal ground on 1 or both sides which causes the problem and necessitates lifting the shield and ground at the receiving end.

 

my recommendation to the OP would be to make up a cable with it connected at both ends and if there is a problem, lift the receiving end, OR sort out proper grounding in your equipment so you can connect it at both ends


Edited by qusp - 12/2/10 at 7:26pm
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