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Working on a low-profile connector for my Schitt Stack, but can't figure out whether my XLR shell grounding pins should be wired up, or not.

Quinton595

Quinton595

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Hello everyone,

I've built myself a custom low-profile connector for my Modius-Jotunheim Schitt Stack. I'm at the point where I'm about to start wiring the pairs of XLR connectors together, and it's a straightforward task. Connect pin 1 male to pin 1 female. Pin 2 male to pin 2 female. Etc.

My confusion comes from the shell grounding tab, shown in the third photo. I can't tell if I should bother connecting it to pin 1 with a jumper, or connecting it to pin 1 with a small capacitor (as I've read in some guides), or just leaving it disconnected.

The box these very short cables pass through is made of wood, so it's not conductive. This means the XLR connector shells that are making an electrical connection with the metal body of the Jotunheim are not electrically connected to the XLR connector shells that are in the Modius. In fact, it means the XLR connector shells aren't electrically connected to anything at all. They sit inert.

If I connect all the Shell Grounding Tabs to their respective Pin-1's, the Jotunheim chassis and the Modius chassis will be electrically connected with a shared ground. Is this good, or bad?

Alternatively, I can just connect the grounding tabs to each other, and NOT to their Pin-1s.



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It won't matter.
While the Audio Engineering Society has a Standard AES 54, that requires the shells to NOT be connected to pin #1.
It really applies to portable cables where the shells may come in contact with metal objects at different potentials.
For permanent component to component installations, there is no reason to not connect the shells.
 
Have you checked how Schiit have connected them? The shell may already be connected to pin 1 and/or chassis. For example see the grounding options in Neutrik's XLR datasheet.

Edit: fixed broken link
 
Last edited:
staticV3 said:
Slightly different context (PA), but should nonetheless be useful:


For more, see "The Pin 1 Problem" here:
https://www.hypex.nl/media/fa/d8/a3/1682342122/The G word.pdf
(PDF DL link)
Click to expand...
Thanks, I'll give this a watch.

Speedskater said:
It won't matter.
While the Audio Engineering Society has a Standard AES 54, that requires the shells to NOT be connected to pin #1.
It really applies to portable cables where the shells may come in contact with metal objects at different potentials.
For permanent component to component installations, there is no reason to not connect the shells.
Click to expand...

So, you're saying for my type of permanent installation, there's no reason NOT to connect the shells to Pin 1, but also, that it won't matter?

somebodyelse said:
Have you checked how Schiit have connected them? The shell may already be connected to pin 1 and/or chassis. For example see the grounding options in Neutrik's XLR datasheet.
Click to expand...
Sorry, what do you mean by checking how Schiit has connected "them"? Connected what, the Jotunheim to the Modius? They sell regular XLR cables, which I can only assume have their casing ground tabs connected internally, to pin 1. But Im not basing that assumption on anything.

How can the shells already be connected to pin 1? As you fan see in my photos, I'm the one building these connectors. The shells aren't connected to anything unless I choose to connect them.
 
I would think that a DMM would easily show what was connected to what. Set it to resistance or continuity -- one probe to pin 1, the other to the shell, and observe the result. :)
 
mhardy6647 said:
I would think that a DMM would easily show what was connected to what. Set it to resistance or continuity -- one probe to pin 1, the other to the shell, and observe the result. :)
Click to expand...
Alright, so, I grabbed a multimeter, and explored around. My findings are as follows:

Jotunheim 2 Balanced Headphone Amplifier: It features female XLR plugs. Pin 1 isn't connected to the latch pin / shell ground tab. The ground tab is also not connected to the chassis (tested via several bare-metal screws on the rear of the amp), nor to anything else. Pin 1 isn't connected to anything else, either.

Modius E Balanced Dac: It features male XLR plugs. Pin 1 isn't connected to the shell ground tab. The shell ground tab is also not connected to the chassis, nor to anything else. Pin 1, however, IS connected to every other pin, in both the Left and Right XLR outputs. In fact, every pin is connected to every other pin, at least with regular continuity testing.
 
Quinton595 said:
How can the shells already be connected to pin 1? As you fan see in my photos, I'm the one building these connectors. The shells aren't connected to anything unless I choose to connect them.
Click to expand...
I thought it would have been clear from the Neutrik datasheet, but I see the link was broken - now fixed. They have 3 options concerning how the panel, shell and pin 1 are (or aren't) connected. One option has the panel, pin 1 and the shell all connected internally, with a paint piercing spike by one of the screw holes so that the manufacturer doesn't need any special panel prep as a good contact will be made when the mounting screw is tightened. Another option has no panel contact, and separate ground (shell) and pin 1 terminals, leaving it up to the manufacturer to connect them if required (say they have the ground lift switch as mentioned in the video in post #2, and a plastic enclosure.) Standard AES48 says manufacturers should connect pin 1 to chassis as close as practical to the connector, which is made easy by Neutrik's option to have panel, shell and pin 1 joined in the connector. Your tests make me wonder what Schiit have done, and whether those models may have a 'Pin 1 Problem' as mentioned at the end of post #2 above, since they appear not to be following AES48. It's possible they've found another non-problematic way to deal with grounding though.
 
staticV3 said:
Slightly different context (PA), but should nonetheless be useful:


For more, see "The Pin 1 Problem" here:
https://www.hypex.nl/media/fa/d8/a3/1682342122/The G word.pdf
(PDF DL link)
Click to expand...

This was a good video, thanks for sharing. Since the body of my DIY connector is made of wood, and can't really pick up noise like a metal connector or mic handle, I think I'm going to leave the ground tab un-connected. I suppose i can always connect it in the future if I detect a hum!

somebodyelse said:
I thought it would have been clear from the Neutrik datasheet, but I see the link was broken - now fixed. They have 3 options concerning how the panel, shell and pin 1 are (or aren't) connected. One option has the panel, pin 1 and the shell all connected internally, with a paint piercing spike by one of the screw holes so that the manufacturer doesn't need any special panel prep as a good contact will be made when the mounting screw is tightened. Another option has no panel contact, and separate ground (shell) and pin 1 terminals, leaving it up to the manufacturer to connect them if required (say they have the ground lift switch as mentioned in the video in post #2, and a plastic enclosure.) Standard AES48 says manufacturers should connect pin 1 to chassis as close as practical to the connector, which is made easy by Neutrik's option to have panel, shell and pin 1 joined in the connector. Your tests make me wonder what Schiit have done, and whether those models may have a 'Pin 1 Problem' as mentioned at the end of post #2 above, since they appear not to be following AES48. It's possible they've found another non-problematic way to deal with grounding though.
Click to expand...

Unfortunately I can't really comment on which approach would work best, as this is all above my knowledge. The Schiit equipment doesn't have a ground lift, which makes me think "Ok, there's no harm in connecting the casing ground", but at the same time, my enclosure is wooden, and my cables are about 2.5 inches long, that's it. That makes me think there's no actual benefit to be gained by connecting them, so i might as well not, and avoid a potential ground loop. I can always connect them in the future, i suppose, if I need to.
 
humankind's single best hum/ground-related troubleshooting tool... the clip lead.
One simply can not have too many clip leads.

1758758472353.jpeg
 
Care to provide a brief overview of what's in it, so non-members can judge whether it's worth $33 to read?
 
I just downloaded it at no cost.
A decade ago, I purchased for $15.

PAPERS
Noise Susceptibility in Analog and Digital Signal Processing Systems.... Nell A. Muncy

Balanced Lines in Audio Systems: Fact, Fiction, and Transformers..............................Bill Whitlock

Grounding Systems and Their Implementation..... Charles Atkinson and Phiip Giddings

Considerations in Grounding and Shielding Audio Devices..............................Stephen R. Macatee

An Easily Implemented Procedure for Identifying Potential Electromagnetic Compatibility

Problems in New Equipment and Existing Systems: The Hummer Test......... John Windt

Automated Test and Measurement of Common Impedance Coupling in Audio System Shield
Terminations.............a Perkins

Fundamentals of Grounding, Shielding, and interconnection................Keineth R. Fause
 
I've found the problem - if you visit with scripts disabled you'll see this message:
This paper costs $33 for non-members and is free for AES members and E-Libary subscribers. Click to purchase paper as a non-member or login as an AES member. If your company or school subscribes to the E-Library then switch to the institutional version. If you are not an AES member Join the AES. If you need to check your member status, login to the Member Portal.
Click to expand...
If you enable scripts on https://aes2.org that text disappears and the download button will work.
 
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