TRS Cable Making...Help!

[MetalBrian]

Hello all,

Haven't posted on here in a while and have recently encountered a problem. The members here are always so helpful so I knew exactly where to turn!

I'm currently making my own audio cables. Over this long weekend, I have made all of my guitar cables, and now I'm on to my TRS and XLR.

I have purchased Mogami and Redco StarQuad balanced cables because I live right in the middle of several apartment complexes and do not want any of the hundreds of cell phone/radio and satellite signals compromising my home recording sessions.

I purchased multi color Mogami Star Quad cables for the patch cords for my patchbay, and black Redco Star Quad for all of the equipment feeding into my patchbay. Many of my cables will be XLR on one end and TRS on the other, ie: my mic pre outputs (XLR) feeding into my TRS patchbay, and also my powered monitors (XLR) hooking into the TRS monitor outs of my Presonus FireStudio Project.

I have seen a lot of information on the internet about only soldering the shield to one connector and leaving the other end "floating". For my purposes, should I do this? I have always been under the impression that I should solder the shield to both ends, but I hear this may cause ground loop issues. Would this apply to all of my TRS to TRS/TRS to XLR cables or only some? Once again, I am making 24 colored Star Quad Patch Cords, as well as, cables to hook my equipment into the patchbay.

Also, the Mogami cable has Blue and Clear cables inside, and the Redco has Blue and White. Which colors are positive and which are negative? I cannot find ANY information about this on the internet...and believe me, I've looked.

Any and all help would be appreciated.

Thanks!

-Brian

[dpd]

Color doesn't matter, pick a convention (e.g. White +, Blue -) and just stick with it. As far as the shielding goes, I connected shields on both ends of thousands of feet of balanced cables throughout a radio station over multiple interconnected studios (including a recording studio) and have had zero ground loop problems - and that's with 17+ KW and 8 KW transmitters just down the hall and antennas 800 feet away. (ok, all the studios are enclosed in copper mesh screen and we have GREAT grounding)

I'd build your cables with the shield connected on both ends and see how things work. Then, if you have problems, clip the shield on one end of some cables and compare results. Just make sure you mark the cable end where the shield is connected as you want that end at the input side of your signal chain.

Good luck!

[FrankDeWitt]

I agree, I would start with shields connected at each end.
You may want to make up a short cable with the shield disconnected to use as a test if you get some hum.

A couple of cautions. You don't want shields connecting to one another between input and output. That means.

Don't connect the shields to the shell of the XLRs
Don't use a patch panel or floor plate ETC that ties the S as in TRS of the 1/4 in connectors together. Very easy to do.

Frank

[MetalBrian]

Hey guys!

Thank you so much for your speedy responses! I can't wait to get started on my Star Quad cables and get ALL of my gear wired in for good :)

I think I GENERALLY understand what you guys are saying: Just solder the shield on both ends. However, I think I got completely lost by this statement:

"You don't want shields connecting to one another between input and output. That means.

Don't connect the shields to the shell of the XLRs
Don't use a patch panel or floor plate ETC that ties the S as in TRS of the 1/4 in connectors together. Very easy to do."

I am SO lost. Haha, as you can probably tell, I am a newbie at soldering. For the amount of cables I need made up, and the high quality, I would've spent thousands. This is a great learning experience for me. Could you explain in Layman's terms what exactly that means?

FYI: My patchbay is a dbx PB-48....if that helps any...

Thanks again guys!

-Brian

[yeahforbes]

Pretty much the only time that you MUST have fully connected shielding is when using phantom power, so don't mess with it on anything to do with mic inputs.

It seems that others make blue hot (tip / pin 2) but it doesn't matter:
http://www.prodigy-pro.com/diy/index.php?topic=2558.0

Personally, I connect the shield only to pin 1 and not the XLR shell lug mostly because it's less work. The debate is as follows...
- Connecting to pin 1 AND the shell means that the shield continues to surround the signal all the time. Like if you hook 2 cables together, that 5 inches of connector is electrically protecting the signal. Since you're so concerned about RF, may as well do it especially if there's any chance of using it in an unbalanced manner.
- Not connecting to the shell means that in the event of some crazy fault where mains voltage is running through your shield, you're less likely to come into contact with it. Like if you have a connector in each hand and you're about to mate them, better to be holding floating metal than connected metal.

I would think that being so careful about the shields of multiple cables being joined by the patchbay's continuous panel is unnecessary except perhaps when multi-building lines are used.

[MetalBrian]

Hey Forbes!

I think I'm understanding this a little better. I really didn't know that TRS and XLR cables were so much more complicated than standard TS instrument cables...good lord!

I'd also like to let it be known that I'm not making any XLR to XLR cables. Only TRS to TRS (patch cables, and the 8 cables going from my Presonus Outputs, 2 from my POD X3, and 2 for my drum machine), and then TRS to XLR-M and TRS to XLR-F (Powered Monitors, Radial X-Amp, and the 4 XLR outs of my Pre Amp to go into the TRS ins on my patchbay)

I'm not sure if that matters any in terms of your explanation, but I figured I'd throw it out there because I'm really not making any mic cables, just balanced line.

So if I understand correctly: When I'm making a TRS to XLR (M or F) I would solder the shield to the Tip on one end, and then to Pin 1 on the other end and for this application I wouldn't need to solder it to the Shell as well on the XLR side? Like I said...I THINK I get it, but I could be totally off base.

And for the TRS to TRS cables: I would solder the shield to the Sleeve on both ends...correct?

Perhaps I'm over thinking this and should just solder the shield on both ends?

Thanks!

-Brian

[FrankDeWitt]

Pretty much the only time that you MUST have fully connected shielding is when using phantom power, so don't mess with it on anything to do with mic inputs.

Snip

- Not connecting to the shell means that in the event of some crazy fault where mains voltage is running through your shield, you're less likely to come into contact with it. Like if you have a connector in each hand and you're about to mate them, better to be holding floating metal than connected metal.
.

A more common reason is ground loops. / hum / buzz

If the shields are connected to the shells then the shields can easily be connected to building ground and / or to each other at any floor pocket. Not a good thing.

If RF is a problem you may want to use these.
http://www.neutrik.com/us/en/audio/204_1603252336/EMC-XLR_Series_productlist.aspx

The fact that your cables are line, not microphone level probably means you will not have any problems anyway. Line is much higher level.

Frank
http://lbpinc.com/DI.html

[FrankDeWitt]

Hey guys!

SNIP

"You don't want shields connecting to one another between input and output. That means.

Don't connect the shields to the shell of the XLRs
Don't use a patch panel or floor plate ETC that ties the S as in TRS of the 1/4 in connectors together. Very easy to do."

I am SO lost. Haha, as you can probably tell, I am a newbie at soldering.

Snip

FYI: My patchbay is a dbx PB-48....if that helps any...

Thanks again guys!

-Brian

Good question. For your application there is probably no issue. It becomes an issue in large rooms with long runs and lots of them (like a church) The cable should leave the board and make it's way to the microphone (or DI) as 3 continuous conductors. (two plus shield.) If it has to go through a few patch panels that is fine. BUT If the patch panel or floor pocket is a metal plate and the XLR connectors in that panel are metal or plastic with a shell ground added then 2 wires make the run ok, but the shields connect to one another at the panel and may connect to the building ground or even to one side of a speaker connection (using 1/4 in jacks in the same floor plate for instance.) These municipal ground paths and "grounds" of different levels can and often do introduce hum.

Again, For your application, probably not an issue but "Best Practice"

[Pinhead]

Simple Brian,

Pin 1 = S = ground
Pin 2 = T = Hot
Pin 3 = R = Cold

Along with all the cables and connectors, make sure you buy the Yamaha Sound Reinforcement Handbook. It's worth more than all your gear combined. It'll answer all your cable questions explicitly in black and white, and spare you a bunch of future posts.

http://www.sweetwater.com/store/detail/YamahaSound/

[madjack]

Hey Forbes!

I think I'm understanding this a little better. I really didn't know that TRS and XLR cables were so much more complicated than standard TS instrument cables...good lord!

I'd also like to let it be known that I'm not making any XLR to XLR cables. Only TRS to TRS (patch cables, and the 8 cables going from my Presonus Outputs, 2 from my POD X3, and 2 for my drum machine), and then TRS to XLR-M and TRS to XLR-F (Powered Monitors, Radial X-Amp, and the 4 XLR outs of my Pre Amp to go into the TRS ins on my patchbay)

I'm not sure if that matters any in terms of your explanation, but I figured I'd throw it out there because I'm really not making any mic cables, just balanced line.

So if I understand correctly: When I'm making a TRS to XLR (M or F) I would solder the shield to the Tip on one end, and then to Pin 1 on the other end and for this application I wouldn't need to solder it to the Shell as well on the XLR side? Like I said...I THINK I get it, but I could be totally off base.

And for the TRS to TRS cables: I would solder the shield to the Sleeve on both ends...correct?

Perhaps I'm over thinking this and should just solder the shield on both ends?

Thanks!

-Brian

Standard convention is: Tip to pin 2, Ring to pin 3, Sleeve to pin 1, don't connect anything to the XLR sleeve lug.