How to connect XLR connector

[made2hack]

Hello,

So as I was reading wikipedia's entry on XLR jacks, it seems there is no clear consensus over whether PIN 1 should connect to the outer jack or simply to pin 1 on the other end.

So, I wanted to get your opinions. On one end, it enters a mixing console. On the other, a microphone to which 48V "phantom" power is provided.

[Anks]

Normally it wont matter as its only the + and - that you are really concerned about as these tend to be a differential signal and cancel out noise. There is a point to the earth pin in that it ensures that both the input and out device are at the same ground potential and in some cases its important to remove hum but can also be the cause of it. I've seen examples were the earth is only connected at one end as to not create a earth loop and have dealt with this many times where more than one power source as been used with a distance of over 100 meters in-between

Also some things are wired differently and are un-balanced and use the earth pin for the negative side (only seen this once or twice).

Connecting the case and pin 1 together is the way I've seen it done on most applications and cant think of anywhere it would be detrimental in anyway.

here is a link to the Rane website that show a lot of different connections un-balanced and balanced with different cables and connectors.
http://www.rane.com/note110.html
In reality some of these cables wont work in certain situations and therefore most are made straight thru and any ground lifting done out of the lead at the device being used or a D.I used to lift the ground.

edit to make it a bit more clear and add link

[made2hack]

Thanks Anks,

Do you by any chance know whether guitar cables are balanced or unbalanced?

[Anks]

Guitar cables are un-balanced as they have no differential signal. On a guitar cable the ring is connected to earth (mainly for safety) and the tip carrys the AC sound wave in reference to that ground.

[Richard Crowley]

The AES (Audio Engineering Society) standard is to NOT connect the connector shell to pin-1/ground/shield/screen.
One of the reasons for this is is so that there isn't a potential ground loop (or WORSE) in case the connector shell contacts some other ground (or HOT) node.

In some cases, in areas where there is high RF noise/interference, some people put a capacitor (~1nF) between pin 1 and the connector shell.  That "grounds" the XLR connector shell at RF frequencies, but not down at audio/power frequencies.

In no case (phantom power or not) is the outer case part of the circuit.

[Anks]

The AES (Audio Engineering Society) standard is to NOT connect the connector shell to pin-1/ground/shield/screen.
One of the reasons for this is is so that there isn't a potential ground loop (or WORSE) in case the connector shell contacts some other ground (or HOT) node.

In some cases, in areas where there is high RF noise/interference, some people put a capacitor (~1nF) between pin 1 and the connector shell.  That "grounds" the XLR connector shell at RF frequencies, but not down at audio/power frequencies.

In no case (phantom power or not) is the outer case part of the circuit.

This is the correct way to do it but as I've said its very common to see cables wired with the pin1 and case connected together.

In theory the chassis and pin one will meet somewhere if not lifted or it wouldn't meet regs.

[made2hack]

Ok, I feel better about not connecting it to the outer shell myself, but that's why I wanted to get some good feedback.

Thanks,

[Gertjan]

Richard Crowley is right.

Read up on the "Pin 1 Problem"
Especially the seminal article "Noise Susceptibility in Analog and Digital Signal Processing Systems" - Neil A. Muncy AES 1995.

Ignoring the Pin 1 problem will give you equipment which is much more sensitive to RF (mobile phones!), plops & clicks etc.

[Anks]

Ignoring the Pin 1 problem will give you equipment which is much more sensitive to RF (mobile phones!), plops & clicks etc.

This is not an issue if the signal is differential. It is better to just have pin1 connected at one end if this was your issue but as these cables are used not just for carrying one type of signal then it would be an issue with different types of signals. Hence just connect pin 1 to pin 1 it will make no difference in 99% of cases and if a ground loop issue arises it should be dealt with in another way.