1 Topic by 0V

  • 0V
  • New member
  • Offline
  • Registered: 2020-10-17
  • Posts: 3

Topic: Shield Connection

Hi everyone,

I have a question regarding the use of shielded cables with my RME Adi-2 Pro. For best performance in the presence of interference ("RFI") I would like to have a circumferential shield contact to the case of the Adi-2 Pro. It seems to me that the chassis connectors are the usual Neutrik ones (A-series or similar) so it does not make sense to use for instance the XLR EMC series, because the chassis contact of the connector shell is made at only one point anyway. Is this correct? If so, do you have any suggestions how to improve shield connectiony?

All the best,

0V

2 Reply by KaiS (edited by KaiS 2020-10-17 16:22:24)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,112

Re: Shield Connection

The XLR's metal shells are automatically connected to chassis when plugged in, nothing to improve here.

The XLR cable shields are connected to chassis and internal ground potential through XLR pin 1 as standard, again nothing can be improved.

If you suffer problems it night be worth to try the Neutrik XLR-EMC's, they do the same thing, a bit more purposely.

In very heavy RF-spoiled environment (close to an transmitting antenna e.g.) double shielded cable can improve things.

Even retrofit ferrite beads exist that can be mounted to existing cables.
You don't need any "audiophile" expensive ones, just the normal cheap ones supplied for computer cables.


What kind of symptoms does your system suffer from?
Don't you just have a ground loop?
RF interference problems can not be observed quite often.

KaiS's Website

3 Reply by 0V

  • 0V
  • New member
  • Offline
  • Registered: 2020-10-17
  • Posts: 3

Re: Shield Connection

Thank you for your reply, KaiS.

KaiS wrote:

The XLR's metal shells are automatically connected to chassis when plugged in, nothing to improve here.

The XLR cable shields are connected to chassis and internal ground potential through XLR pin 1 as standard, again nothing can be improved.

If you suffer problems it night be worth to try the Neutrik XLR-EMC's, they do the same thing, a bit more purposely.

Yes, shield, shell, and pin 1 are connected to chassis as standard. But my impression is that the shield connection is not circumferential (360 degrees) even when I use the XLR EMC series, in particular the female version with the gasket. The reason for this is that the chassis connectors are plastic and hence the shield connection is made, more or less, via a pigtail, which has suboptimal EMC performance (see, e.g., http://www.hottconsultants.com/pdf_files/aes-2007.pdf)). If my impression is wrong, please let me know.
 

KaiS wrote:

In very heavy RF-spoiled environment (close to an transmitting antenna e.g.) double shielded cable can improve things.

Yes. If the shield connection to the chassis is via a pigtail you can basically use as may shield layers as you want, but the shielding efficientcy remains low.

KaiS wrote:

Even retrofit ferrite beads exist that can be mounted to existing cables.
You don't need any "audiophile" expensive ones, just the normal cheap ones supplied for computer cables.

Essentially yes, but why not use the shield of a shielded cable to its full potential? ;-)

- 0V

4 Reply by KaiS (edited by KaiS 2020-10-17 17:45:54)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,112

Re: Shield Connection

The main question is unanswered:
What's the symptoms you have with RF interference?

The shield connection to chassis is via the internal screws, pathlengh in the range of a centimeter.
No "pigtail" anywhere.
So it's valid up to ca. 30 GHz.

Far out of the range where standard cable shields are specified or functional.


RF compliance is mainly a question of an intelligent design.
I never had any RF related problem with any RME device yet.

E.g. I have 3 Smartphones within centimeters next to my ADI-2 Pro and nothing happens when someone calls in.

KaiS's Website

5 Reply by 0V

  • 0V
  • New member
  • Offline
  • Registered: 2020-10-17
  • Posts: 3

Re: Shield Connection

KaiS wrote:

The main question is unanswered:
What's the symptoms you have with RF interference?

The shield connection to chassis is via the internal screws, pathlengh in the range of a centimeter.
No "pigtail" anywhere.
So it's valid up to ca. 30 GHz.

My main question is whether it is possible to have a 360 degree shield connection to chassis or not. This is why I started the thread. Your answer seems to be "No", which confirms my impression. Whether a 1cm (guess?) pigtail is a problem or not depends on many factors like interference strength, installation, cable lengths etc, so I would prefer to stick to a discussion of the shield connection.

6 Reply by KaiS (edited by KaiS 2020-10-17 20:43:16)

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,112

Re: Shield Connection

0V wrote:
KaiS wrote:

The main question is unanswered:
What's the symptoms you have with RF interference?

The shield connection to chassis is via the internal screws, pathlengh in the range of a centimeter.
No "pigtail" anywhere.
So it's valid up to ca. 30 GHz.

My main question is whether it is possible to have a 360 degree shield connection to chassis or not. This is why I started the thread. Your answer seems to be "No", which confirms my impression. Whether a 1cm (guess?) pigtail is a problem or not depends on many factors like interference strength, installation, cable lengths etc, so I would prefer to stick to a discussion of the shield connection.

What are your questions, still unanswered?

KaiS's Website