XLR cable conundrum

[AUDIO FREQ]

Hi guys, its me again...your favorite annoying noob.

So I had an interesting dilemma today. A friend of mine bought a long xlr cable from guitar center, and there was quite a bit of white noise. It's about a 30 ft xlr cable, generic. I unscrewed the connector, and noticed, 1 - ground, 2 hot, 3 cold...and then part of the ground that goes to 1 (half of the copper strands), is soldered to the metal tab.

Why is this like this? Is this how it's supposed to be? I thought it was supposed to be 1-ground, 2-hot, 3-cold, and Bob's your uncle.

 

[totoxraymond]

1 is shield, not ground. And shield should be connected to the metal chassis at either end of the cable.

Are you sure noise is coming from the xlr? 30ft / 10m seems rather short to me. It would have to be a really bad cable to generate any meaningful noise by itself.

What was it used for?

 

[AUDIO FREQ]

1 is shield, not ground. And shield should be connected to the metal chassis at either end of the cable.

Are you sure noise is coming from the xlr? 30ft / 10m seems rather short to me. It would have to be a really bad cable to generate any meaningful noise by itself.

What was it used for?

Aren't shield and ground the same? Have I been calling pin 1 the wrong thing this whole time?

 

[Khron]

Pin 1 usually goes to ground. Shield, if used, goes to the XLR connector shell. Inside microphones, the two terminals are usually connected together at the XLR connector itself.

 

[AUDIO FREQ]

Pin 1 usually goes to ground. Shield, if used, goes to the XLR connector shell. Inside microphones, the two terminals are usually connected together at the XLR connector itself.

Ahhhhh ok! So it depends on where pin 1 is connected on said device. What about a Sony C100 condenser microphone into a mic preamp of the interface? The Sony C100 XLR diagram attached.

 

[Newmarket]

XLRs really have four connection points as you have seen. But bypassing all the details about current recommended practice and how this is not always what you find in equipment - cables / connectors don't usually cause broadband noise. Screening issues may cause "hum and buzz" - through ground issues and lack of proper RFI screening. But white noise seems more like a problem with the equipment itself. Look at the gain staging. Is there excessive amplification in the signal chain ?

 

[Barry Hufker]

Here's a link with more information as to how your cable is terminated...https://repforums.prosoundweb.com/index.php?topic=37510.0

 

[AUDIO FREQ]

XLRs really have four connection points as you have seen. But bypassing all the details about current recommended practice and how this is not always what you find in equipment - cables / connectors don't usually cause broadband noise. Screening issues may cause "hum and buzz" - through ground issues and lack of proper RFI screening. But white noise seems more like a problem with the equipment itself. Look at the gain staging. Is there excessive amplification in the signal chain ?

Well, I noticed the mic needed quite a bit of gain from the Apollo Twin X, and it became noisy (white noise). I ended up cutting the shield (4th solder point) on both ends of the xlr cable and reconnected it. The noise went away, and the microphone had tons of gain and was very sensitive, with only a little boost from the pre-amp. But I started getting computer-ish noises. This is the RFI noise I am assuming?

 

[AUDIO FREQ]

Here's a link with more information as to how your cable is terminated...https://repforums.prosoundweb.com/index.php?topic=37510.0

Thank you Barry, I will read!!!!

 

[ccaudle]

1 - ground, 2 hot, 3 cold...

The terminology changed over time to be more explicit. The Audio Engineering Society (AES) maintains standards to help interoperability between different vendors, and the current standard for XLR style connectors is AES-14-1992-S2014; that document lists pin 1 as being "Screen (shield)."
In the past you did often see pin 1 referred to as the "ground" pin, but that is ambiguous and does not make clear that it should be connected to chassis (which is often connected to safety earth/power ground) and not the circuit power supply reference point (often referred to as "circuit ground").

then part of the ground that goes to 1 (half of the copper strands), is soldered to the metal tab.

That is sometimes done to enforce the "pin 1 connects to chassis at the end device" requirement for proper shielding, but is counter to AES-51-1 which specifies that the shield should connect only to pin 1 of the cable connector and not to the connector shell.
The reason for that requirement is that if the shield connects to the shell, if the shell contacts building metal (in a commercial building all exposed metal is required to be tied to the safety earth system) there can be power supply related currents flowing unexpectedly through the cable shield to the connected equipment. That can cause noise problems in susceptible equipment, and in general can be a nuisance because the noise behavior changes depending on where the cables are lying.

That noise susceptibility from cables contacting the building safety earth would be a 60Hz hum in North America (50Hz in much of the rest of the world), and is not really the same thing as the white noise you are describing.

I ended up cutting the shield (4th solder point) on both ends of the xlr cable and reconnected it. The noise went away, and the microphone had tons of gain and was very sensitive, with only a little boost from the pre-amp

The description of the mic becoming more sensitive sounds like possibly some of the shield strands had come loose and were touching either pin 2 or pin 3 in addition to pin 1 and the shell tab, i.e. shorting one of the signal pins. Did you notice if that could have been the situation?
Does the microphone require phantom power? For a dynamic microphone shorting one pin to shield would make it more susceptible to noise pickup, but if it reduces the sensitivity at all should not be by more than 6dB. The large decrease in sensitivity you describe I would expect if a phantom powered mic had one leg of the phantom power shorted to shield.

 

[AUDIO FREQ]

The terminology changed over time to be more explicit. The Audio Engineering Society (AES) maintains standards to help interoperability between different vendors, and the current standard for XLR style connectors is AES-14-1992-S2014; that document lists pin 1 as being "Screen (shield)."
In the past you did often see pin 1 referred to as the "ground" pin, but that is ambiguous and does not make clear that it should be connected to chassis (which is often connected to safety earth/power ground) and not the circuit power supply reference point (often referred to as "circuit ground").



That is sometimes done to enforce the "pin 1 connects to chassis at the end device" requirement for proper shielding, but is counter to AES-51-1 which specifies that the shield should connect only to pin 1 of the cable connector and not to the connector shell.
The reason for that requirement is that if the shield connects to the shell, if the shell contacts building metal (in a commercial building all exposed metal is required to be tied to the safety earth system) there can be power supply related currents flowing unexpectedly through the cable shield to the connected equipment. That can cause noise problems in susceptible equipment, and in general can be a nuisance because the noise behavior changes depending on where the cables are lying.

That noise susceptibility from cables contacting the building safety earth would be a 60Hz hum in North America (50Hz in much of the rest of the world), and is not really the same thing as the white noise you are describing.



The description of the mic becoming more sensitive sounds like possibly some of the shield strands had come loose and were touching either pin 2 or pin 3 in addition to pin 1 and the shell tab, i.e. shorting one of the signal pins. Did you notice if that could have been the situation?
Does the microphone require phantom power? For a dynamic microphone shorting one pin to shield would make it more susceptible to noise pickup, but if it reduces the sensitivity at all should not be by more than 6dB. The large decrease in sensitivity you describe I would expect if a phantom powered mic had one leg of the phantom power shorted to shield.

Hmm, that could. be a possibility, the XLR connectors were soldered on very poorly, no heat shrinking, dull solder joints...etc. I will snip completely, desolder old stuff, and re-solder cleanly thank you!

 

[kags]

Also make sure your Apollo is not running any virtual preamp plugins, which might contribute some noise or change the sensitivity.

With the UAD control panel it’s easy to have insets or routings that are not the purest record or monitor path.

Also be sure the noise is not being added By the headphone amp or monitor chain.

 

[AUDIO FREQ]

Also make sure your Apollo is not running any virtual preamp plugins, which might contribute some noise or change the sensitivity.

With the UAD control panel it’s easy to have insets or routings that are not the purest record or monitor path.

Also be sure the noise is not being added By the headphone amp or monitor chain.

Thats a good idea, maybe I should buy a hp amp, instead of using a 1/4 splitter Y cable to power a DT 770 PRO and a Sony MDR 7506 at the same time.

Any suggestions?

 

[MicMaven]

maybe I should buy a hp amp, instead of using a 1/4 splitter Y cable to power a DT 770 PRO and a Sony MDR 7506 at the same time.

I rather doubt that is causing the white noise you are hearing. Nevertheless, you may be on to something as Y-splitters are ... ahem ... um ... somewhat, sorta kinda contraindicated. See this article by RANE Corporation on it. If nothing else, they impose a 3 dB loss in each side of the Y cable. This happens in antenna splitters and other cases when you split the signal - usually causing the listener to turn the volume up and that, alone, can cause noise - reference the previous comments from smarter guys about gain staging and other input volume settings. Note - I am NOT being critical - just thinking this may add something useful to your audio connection tool box. James

https://www.ranecommercial.com/legacy/pdf/ranenotes/Why_Not_Wye.pdf
Another copy
https://www.prosoundweb.com/rane-note-why-not-wye-or-y-for-that-matter/

 

[AUDIO FREQ]

I rather doubt that is causing the white noise you are hearing. Nevertheless, you may be on to something as Y-splitters are ... ahem ... um ... somewhat, sorta kinda contraindicated. See this article by RANE Corporation on it. If nothing else, they impose a 3 dB loss in each side of the Y cable. This happens in antenna splitters and other cases when you split the signal - usually causing the listener to turn the volume up and that, alone, can cause noise - reference the previous comments from smarter guys about gain staging and other input volume settings. Note - I am NOT being critical - just thinking this may add something useful to your audio connection tool box. James

https://www.ranecommercial.com/legacy/pdf/ranenotes/Why_Not_Wye.pdf
Another copy
https://www.prosoundweb.com/rane-note-why-not-wye-or-y-for-that-matter/

Thank you, ill check that out!

 

[kags]

Headphone splitters with a couple pairs of headphones will put a load on the headphone amp but shouldn’t increase noise in any meaningful way. I think the UA interfaces have decent power, but I’ve never listened critically for noise. If the amp is noisy, you will hear the noise floor without any signal (from the mic or DAW playing, so you should be able to tell if the amp is adding noise or if the mic/preamp/processing is creating the noise.

In any case, the built-in headphone amp is used by a lot of professionals, so it is certainly acceptable and if high enough quality for professional work.

 

[RCAguy]

Hi guys, its me again...your favorite annoying noob.

So I had an interesting dilemma today. A friend of mine bought a long xlr cable from guitar center, and there was quite a bit of white noise. It's about a 30 ft xlr cable, generic. I unscrewed the connector, and noticed, 1 - ground, 2 hot, 3 cold...and then part of the ground that goes to 1 (half of the copper strands), is soldered to the metal tab.

Why is this like this? Is this how it's supposed to be? I thought it was supposed to be 1-ground, 2-hot, 3-cold, and Bob's your uncle.

When a newbie, I connected XLR shells to cable shields, along with pin1 - I’ve since disconnected those shells, as touching them they can impart a shock, and induce RFI (often manifest as “white noise”) in the audio. The separate connection is XLR’s advantage over TRS connectors, where the shell is the shield.

 

[DarkSky]

The separate connection is XLR’s advantage over TRS connectors, where the shell is the shield.

Not necessarily.

While many older TRS socket designs attach the "S" connection directly to the chassis mechanically, there are a number of insulated types that allow the shield to float (unless explicitly routed to the chassis or circuit 'ground').

If you use that type of TRS socket, then TRS is the functional equivalent of XLRs that don't have pin 1 connected to the shell.

 

[Rusan]

I know it won't solve the root cause of the problem, but have you tried connecting Pin 1 to the XLR body terminal with something like a .1uF ceramic capacitor?

 

[Newmarket]

I believe the "something touching the connector" shell issue is relevant only in a case such as where cables are joined together to extend them and the mated connector shells then come onto contact with other metal structures that are most likely "earthed". This isn't really going to happen at equipment interfaces.
Or where eg a user carries a static charge relative to "earth" and there is, naturally, a discharge when they touch the "earthed" connector shell. This might also happen of course if they touch a conductive chassis etc.
On the upside the user id now discharged
All points to some degree of "Pin 1 problem".
For (not really) completeness there are alternative ways to connect eg a "four conductor" as proposed by @thor.zmt . But that is a non-standard consideration.