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Topic: Help with XLR Wiring (Read 6537 times) previous topic - next topic
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Help with XLR Wiring

Hello Everyone

I will shortly be re-wiring an analogue radio studio. The cable I have selected is shielded CAT5e, like this. One end of the cable will be terminated with an XLR connector, the other will go into a Krone block.

Please can you advise me if it is necessary to connect the drain wire in the CAT5e cable to pin one of the XLR? I have done a lot of reading online; some say not to connect anything to pin one, others say to do so. My goal is to get an audio signal which is as clean and interference free as possible.

Also, what do I do with the drain wire at the end which will go into the Krone block? Does it need to be connected to anything at that end?

Finally, the actual shielding around the cable pairs, does that need to be connected to anything or is that what the drain cable is for?

The wiring will be carrying balanced audio between professional studio equipment, over relatively short cable runs.

I hope you can help with my confusion  :)

Braunschweig

Re: Help with XLR Wiring

Reply #1 –
Using CAT5e for XLR balanced interconnect wiring is the next new thing.  Some say that it doesn't even need to be shielded CAT cable.  But if it is shielded CAT cable, the shield should always be connected at the send end. Different experts have different views on the receive end. Some say that it should always be connected, some say that it should never be connected and other say that it should be a hybrid connection using a small capacitor.

********************
 Cables for phantom powered mics always need the shield connected at both ends. But I think this this installation is about line level cables.
Kevin Graf :: aka Speedskater

Re: Help with XLR Wiring

Reply #4 –
Quote from: Braunschweig on
Hello Everyone

I will shortly be re-wiring an analogue radio studio.

Why?

Quote
The cable I have selected is shielded CAT5e, like this.

Why?

Quote
One end of the cable will be terminated with an XLR connector, the other will go into a Krone block.

I never heard of this before but a quick trip trough Wikipedia showed that it is the European, newer tech, probably higher cost alternative  to the time-honored (in the US) 110 block or punch-down block for terminating CAT-series telephone cables.

One end is usually preterminated with a multicore cable, usually twisted pair solid number 24 or so, probably unshielded.

The other end (the end that is punched down) usually has some dedicated purpose.


Quote
Please can you advise me if it is necessary to connect the drain wire in the CAT5e cable to pin one of the XLR?

Maybe, maybe not.

There's an old saying - the pioneers are the ones with arrows in their back. How does it feel being a guinea pig?


The answer to this depends on the equipment at both ends of the cable. If you were doing this with a traditional solution, every pair in the multicore shielded cable has its own shield and drain wire.  The drain wire typically goes to the XLR pin 1, natch.

Quote
I have done a lot of reading online; some say not to connect anything to pin one, others say to do so.

And those my friend are examples of the arrows that pioneers gather.

Quote
My goal is to get an audio signal which is as clean and interference free as possible.

Easy answer - don't be a pioneer. Stick with tradition.

Quote
Also, what do I do with the drain wire at the end which will go into the Krone block? Does it need to be connected to anything at that end?

Typical practice is to have a dedicated drain wire for every pair, and hook it to the pin of the corresponding XLR, TRS or similar cable.

Quote
Finally, the actual shielding around the cable pairs, does that need to be connected to anything or is that what the drain cable is for?

asked and answered.

Quote
The wiring will be carrying balanced audio between professional studio equipment, over relatively short cable runs.

Length generally doesn't matter when it comes to shielding and grounding. You can has as bad grounding problems with a 18" cable as a 100 foot cable.

Interested in the answers to my "Why" questions.

Most of the time successful pioneers are the guys who have already duked it out with every tribe of Indian on the prairie and lived to tell.  Being both a newbie and a pioneer is like asking for trouble, even sending a check along to make sure you get it.

Re: Help with XLR Wiring

Reply #5 –
I think that all the pioneers settled down, built homes and had children. Steve Lampen @Beldn wrote about the subject way back in 2002.
Has for why one might use Cat cable for analog signals:
a] More economical.
b] Ease of installation.
c] Many balanced cables are not fire rated for in-wall installation. The ones that are rated often have SCIN problems.
Kevin Graf :: aka Speedskater

Re: Help with XLR Wiring

Reply #6 –
Quote from: Speedskater on
And a Belden Blog:
"The Strange World of Cat 5e and Cat 6"
http://www.belden.com/blog/broadcastav/The-Strange-World-of-Cat-5e-and-Cat-6.cfm

I always thought that using network cable for analogue audio was just an audiophool fad. Seems it might not be as phoolish as I thought.
The most important audio cables are the ones in the brain

Re: Help with XLR Wiring

Reply #7 –
Most CAT5 or 6 cables are fine with line level analog audio without shielding as long as the connected equipment is reasonably RF immune.  Cell phones and possibly WiFi are the latest issue, as much legacy equipment was not designed to be immune to those frequencies, and you get a pretty high field strength next to the device.  Actually plain old unshielded twisted pair works well in most applications at line level.. again except for RF susceptability.

It has been shown that unshielded CAT6 cable works acceptably at mic level, if you use phantom power, of course you will have to connect the pin ones on XLR's on both ends.  It works  because that the very tight pitch of the twists and careful attention to balance cancel out most external fields.

The real issue is that almost all CAT cables are solid wire,  I can tell you from personal experience that solid wire can be a serious issue when it comes to conductor breakage.  Back in the 1970's I was Chief Engineer and Assistant Chief of two radio stations wired with solid wire.  Both had multiple issues with broken conductors, both at connectors and in the middle of cables subject to regular flexing.  I never saw issues at IDC connectors like 66 or 110 blocks, and rarely in the middle of moderate to high pair count cables.  The problem was in single or 2 or 3 pair cables subject to flexing.

Now I recently took over as Chief at a different station wired with CAT5 and 6.  I've already run into several issues with broken wires at XLR's and particularly the green euro connectors.  Don't forget, a stranded wire has typically 7 strands, all of which have to break for the conductor to fail.  Solid wire has only one strand to break.

If you go the CAT6 route first you want to be very careful stripping the wire.  The slightest nick in the copper conductor will break when flexed a few times.  In euro connectors, strain relief is important, and be careful about overtightening, which can deform the conductor and make it prone to breakage.  And I don't see how you can terminate CAT5/6 in a typical XLR or phone plug with any type of strain relief.

On the other hand, CAT5/6 makes excellent trunks when terminated on telco style blocks, usually without shielding.  And you can punch down many types of stranded wire on those blocks.  You may find that you have to strip the conductors before punching down, as the IDC block terminals may not have enough pressure to displace the insulation on some stranded audio cable.  If you use the standard stranded audio cable on the "outside" side of the block, you can solder it to an XLR and have a rugged connection.

The matter of where to ground the shields in audio wiring has been the subject of extensive discussion and a fair amount of research by members of an AES standards group I belong to.  There are several resulting standards.  AES54 is the most pertinent.  If you are an AES member, it is free to download, otherwise you have to pay.  Basically, if the equipment is properly designed (all too much isn't) and your cable doesn't have SCIN (Shield Current Induced Noise) (unfortunately most foil shielded twisted pair with a drain wire has SCIN), then the best shielding, particularly for RF immunity, is to ground the shield at both ends.  If you have pin one hum problems, ground only one end, and if you then have RF issues, bypass the ungrounded end of the shield to the case of the device with let's say a 1000 PF disc capacitor.  Again, at line level, well designed balanced audio interfaces should make this academic, they should work fine with both shields grounded, with either end grounded and the other end floating, with the shield left floating, or with no shield at all, all as long as the pair is well twisted.

Re: Help with XLR Wiring

Reply #8 –
Jim Brown has several papers on the 'Pin 1 Problem' and Shield Current Induced Noise'.
http://www.audiosystemsgroup.com/publish.htm

*****************************************
The AES has a 85 page reprint journal of some of the best papers on this subject and it's only $15.
"Shields and Grounds"
https://customer258769455.portal.membersuite.com/onlinestorefront/BrowseMerchandise.aspx?contextID=dfb59c4a-0066-cfc7-defb-0b3b8d837468
Kevin Graf :: aka Speedskater

Re: Help with XLR Wiring

Reply #11 –
Quote from: Speedskater on
Jim Brown has several papers on the 'Pin 1 Problem' and Shield Current Induced Noise'.
http://www.audiosystemsgroup.com/publish.htm

*****************************************
The AES has a 85 page reprint journal of some of the best papers on this subject and it's only $15.
"Shields and Grounds"
https://customer258769455.portal.membersuite.com/onlinestorefront/BrowseMerchandise.aspx?contextID=dfb59c4a-0066-cfc7-defb-0b3b8d837468


Probably the most important information in this pay-for document can be obtained here for free:

http://www.rane.com/note110.html

and

https://shure.custhelp.com/ci/fattach/get/97648/0/filename/Ground+Loop+_Bill+Whitlock.pdf

Re: Help with XLR Wiring

Reply #12 –
Quote from: schmidj on
The real issue is that almost all CAT cables are solid wire,  I can tell you from personal experience that solid wire can be a serious issue when it comes to conductor breakage.  Back in the 1970's I was Chief Engineer and Assistant Chief of two radio stations wired with solid wire.  Both had multiple issues with broken conductors, both at connectors and in the middle of cables subject to regular flexing.  I never saw issues at IDC connectors like 66 or 110 blocks, and rarely in the middle of moderate to high pair count cables.  The problem was in single or 2 or 3 pair cables subject to flexing.

AFAIK the time-honored rule of thumb is that if the installation is fixed, solid wire generally gets the job done. By fixed, I mean that both ends of the wire and regular points along the way if its more than a few inches long are tightly fastened to the same rigid mechanical object, say inside an equipment chassis.  These can last for as long as the wire's insulation lasts which can at this point be over a century.

The opposite extreme is IME a mic cable that is used in a touring live performance.  These can be unusably unreliable even if wired with stranded wire.  If you want these to last you use stranded wire for the fine reasons that were given in the post I'm responding to, but in addition all can be lost without adequate stress relief.  The importance of stress relief can be appreciated if you end up being a heavy user of CAT-5 cables with solid conductors. They generally last well enough if terminated with industry spec RJ45 connectors which include strain relief if properly installed.  But, no way would I put them on a mic for a lead performer in a touring show.

Final anecdote - the worst duty I ever put a mic cable on was a lead singer in dedicated venue show. Low duty cycle - just 2 rehearsals and 2 45 minute musical sets a week. But, he liked to twirl his mic cable and swingh the mic about,  and the like and I was yet again rebuilding his mic cables again and again after upgrading the cables and connectors to the best I had.  One time his mic cable had 4 separate intermittent opens in it, but most of the time they all were intermittently passing signals. Final solution - a wireless mic!

Re: Help with XLR Wiring

Reply #14 –
Quote
But, he liked to twirl his mic cable and swingh the mic about,
:D :D I've seen video of The Who where Roger Daltrey's mic cable is doubled-back and tapped to the mic.    The cable may not have lasted for much more than one performance, but hey,  destroying equipment was a part of their act at one time.     If you watch the video of their Monterey Pop performance, you see one of the sound guys rescuing a mic & stand as they are wrecking their instruments & amps.

Re: Help with XLR Wiring

Reply #15 –
Quote from: DVDdoug on
Quote
But, he liked to twirl his mic cable and swingh the mic about,
:D :D I've seen video of The Who where Roger Daltrey's mic cable is doubled-back and tapped to the mic.    The cable may not have lasted for much more than one performance, but hey,  destroying equipment was a part of their act at one time.    If you watch the video of their Monterey Pop performance, you see one of the sound guys rescuing a mic & stand as they are wrecking their instruments & amps.

Destroying a well-made mic cable can be pretty tough even if that is exactly what you want to do.

For example, some pro mic cables are made out of 18 gauge finely stranded wire - lots more than 7 strands, and any one of them can handle the signal. The lore of roadies includes any number of tales about using mic cables for lashing down gear on the road, and for the intended purpose at the show. No problems.

My lasso-artist lead vocalist took about 6 months to harm ,my later production mic cables. One key: Neutrik XLR connectors.  I bought cables with all sorts of  band name and off-brand connectors and many of them were just fine. But the ones that did not pass muster got the Neutrik treatment next time I fired up my soldering iron.  Usually, that was enough to fix 'em forever.

On a slightly different topic,, while it need not be so, most the punch-down block solutions I see end up forcing you to hook all of the pin 1's of everything that has a pin one to the same conductive bus. Of course, if you don't do that, it is still a option if that is what you want to do. But, if you are force-fed hooking all the pin 1's together, leaving any pair of them isolated and running between the pin 1s on the two relevant pieces of gear stops being an option. 

I like options when I'm setting up a complex system.

Re: Help with XLR Wiring

Reply #16 –
Quote from: Arnold B. Krueger on
Quote from: Speedskater on
A new thread on analog audio and CAT cable:
http://groupdiy.com/index.php?topic=63763.msg807313#new
Broken link.  -whole site, not just this thread.
The groupDIY forum recently updated their forum firmware and all sorts of strange things started happening.

The URL:
www.groupdiy.com stopped working.
but
groupdiy.com worked. Don't know why or how www. could break a URL.
Kevin Graf :: aka Speedskater

Re: Help with XLR Wiring

Reply #17 –
My webhosting company makes me fill in whether my sites are to work with WWW, without, or both.  Also when providing DNS info for domain registration, WWW. is a separate subdomain (I think that is the term, I forget)  from the domain without the WWW and requires separate entries.  You could have them point to different links.  Would probably make no sense, but possible.

Re: Help with XLR Wiring

Reply #18 –
IIRC, it would be server.subdomain.[subdomains].domain. So "www" is actually the name of the machine running the webserver.

it doesn't have to be. And, I suppose, it doesn't have to have a name at all, as the router would be configured to send incoming web traffic to the appropriate machine.

But "www" (an "abbreviation" that has more syallables (9) than letters (3)) is such an established convention that it is a bit silly not to follow it.

From the user point of view, your browser will try prefixes and suffixes.

The most important audio cables are the ones in the brain

Re: Help with XLR Wiring

Reply #19 –
Domains and subdomains have very little to do with the machines they resolve to. A domain owner may set a wildcard, or any subdomain to different IP addresses.

When this failure was first announced, I checked what would happen if I fed a www. before the domain for that site. It appears the owner resolves it to the same exact IP address, and the web server sitting behind that IP address is configured to forward "www." prefixed requests to the "naked" domain, as in no subdomain. I did not test whether it also forwards the entire path in the process.
 

Re: Help with XLR Wiring

Reply #20 –
Quote from: Speedskater on
A new thread on analog audio and CAT cable:
http://groupdiy.com/index.php?topic=63763.msg807313#new
Quote from: Speedskater on
A new thread on analog audio and CAT cable:
http://groupdiy.com/index.php?topic=63763.msg807313#new

Nice little forum you have there - great place to go to be personally attacked by the moderators.