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Author Topic: 1/8" to XLR  (Read 6008 times)

Dan Richardson

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1/8" to XLR
« on: February 01, 2011, 07:20:54 pm »

I have a cable wired 1/8" stereo to 2 XLRs, for plugging my whatever into a desk that only has XLR inputs.
Someone mentioned that phantom power will blow up an iPhone's output stage.
That would be bad.
Yes, I can turn off the phantom on most desks, but things happen.
I don't want to carry around a pair of DIs just for this application.
Is there a safe way to wire this?
What happens if I leave the XLR pin 1 open, and wire pin 3 to shield and pin 2 to signal?
Is this a reasonable electronic solution?
Are there boards with phony balanced inputs where this will cause issues?
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Geoff Doane

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Re: 1/8" to XLR
« Reply #1 on: February 01, 2011, 09:47:12 pm »

What happens if I leave the XLR pin 1 open, and wire pin 3 to shield and pin 2 to signal?
Is this a reasonable electronic solution?
Are there boards with phony balanced inputs where this will cause issues?

That should work, although the two pins-3 will be common to each other (still shouldn't be a problem that I can see).

If you run into an unbalanced XLR input (very rare these days, I think), it shouldn't be a problem either, as long as the XLR is wired pin-2 hot.  If it isn't, it just won't work.  It shouldn't damage anything.

Building an adapter with a 10 μF, 63V cap in series with pin-2 might be an even better idea.  Connect pin-1 and -3 to the shield of the TRS.  This might cause current to flow from pin-3 to -1, but that's only a problem with transformer inputs (could magnetize the transformer), which are also rather rare these days.

GTD
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Gareth Marsh

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Re: 1/8" to XLR
« Reply #2 on: February 02, 2011, 12:59:32 am »

I made the same cables, and used to use them with inline transformers to prevent this happening.

One day, I was on a system that had far greater issues and the transformers were used somewhere else. House techs had global phantom on (without any input needing it), I hooked in my macbook without thinking, and that was the end of the headphone output.

I have just been very careful since then, but I have thought about blocking caps, or even if I could cram a transformer into an XLR shell somehow (this would also help with noisy laptops).


Gareth
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Josh Bennett

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Re: 1/8" to XLR
« Reply #3 on: February 02, 2011, 02:01:33 am »

are you connecting this in a way to get stereo? XLR(L) pin2 to 1/8" tip, pin3 to 1/8" sleeve; XLR(R) pin2 to 1/8" ring, pin 3 to 1/8" sleeve. That would work against phantom damage, but will insert any ground noise from your laptop or other device directly into the signal stream.
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Frank DeWitt

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Re: 1/8" to XLR
« Reply #4 on: February 02, 2011, 11:57:21 am »

What your suggesting should work OK on battery powered devices. such as a I-pod. (Keep the output low, as earphone output is close to line level.

I can imagine some strange things happening with any powered device such as a laptop.  (If both are properly grounded, then you have reconnected pin 1)

A DI box provides protection and ground isolation and gets the level right for a mic in so it is a very nice solution.  If you only need Mono you could build a 3 resistor summing cord,  http://www.rane.com/note109.html  Then you would just need 1 DI box, and some of them are quite small.

Disclaimer, I build and sell DI boxes.

Frank   http://lbpinc.com/DI.html
« Last Edit: February 02, 2011, 11:59:40 am by Frank DeWitt »
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Fred Dorado

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Re: 1/8" to XLR
« Reply #5 on: February 02, 2011, 01:00:33 pm »

why not just a stereo di, it would give you more options, you would only need to carry one, it would provide protection and the ability to use 1/8 or even rca connectors is nice, I think some even do 1/4 along with the others.

This is what we use, it's cheap, small and would protect equipment and you would need a specialty cable, allowing the xlrs used for this to be use somewhere else when not needed

http://www.audiopile.net/products/DI_Boxes/DBRC-2A/DBRC-2A_cutsheet.shtml
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Dan Richardson

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Re: 1/8" to XLR
« Reply #6 on: February 03, 2011, 11:39:19 pm »

The re-grounding pin 1 issue is the kind of thing I was afraid I was missing.
My pack is frequently insanely tight for both size and weight.
A couple pounds and the size of most DIs is actually an issue.
I'd also rather not have a mediocre xformer inline where a straight wire could be,
and good xformers cost money.
That said, both the DIs presented were interesting options. Frank, that box of your is lovely. Have you got room in there for another xformer and another XLR?

Meantime, I'll scrounge up a couple of caps and give that a try.
Thanks, all.
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Weogo Reed

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Re: 1/8" to XLR
« Reply #7 on: February 04, 2011, 01:04:42 am »

Hi Dan,

How about this? :

 http://www.galaxyaudio.com/JIBR.jsp

Stayin' warm up your way?!

Good health,  Weogo
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JamesButera

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Re: 1/8" to XLR
« Reply #8 on: February 04, 2011, 02:13:27 pm »

Didn't check the weight, but if you can fit it the Radial JPC is a great DI that you can use for more than just iPod.

http://www.radialeng.com/di-jpc.htm
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Daniel Cash

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Re: 1/8" to XLR
« Reply #9 on: February 04, 2011, 05:53:38 pm »

Unless you are sending the signal a long distance, why hassle with balanced connectors with a risk of phantom power? Just use the 1/4" line inputs.   I use a cable like this for the job, and never had a problem.   Am i missing something obvious?
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Frank DeWitt

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Re: 1/8" to XLR
« Reply #10 on: February 04, 2011, 10:17:28 pm »

Unless you are sending the signal a long distance, why hassle with balanced connectors with a risk of phantom power? Just use the 1/4" line inputs.   I use a cable like this for the job, and never had a problem.   Am i missing something obvious?


Yes,  He said his desk has only XLR

BTW  A good quality Jensen transformer DI box can weigh 10 oz

Frank
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Dan Richardson

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Re: 1/8" to XLR
« Reply #11 on: February 05, 2011, 01:30:13 pm »

@Weogo, I'm perversely fond of stereo for my sound check and preshow, even though I basically never pan anything during a show.

@James, the Radial stuff is beautiful, but the case weighs more than I want to carry, let alone the xformers and the price tag.
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Thomas Dameron

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Re: 1/8" to XLR
« Reply #12 on: February 08, 2011, 07:04:39 pm »

Unless you are sending the signal a long distance, why hassle with balanced connectors with a risk of phantom power? Just use the 1/4" line inputs.   I use a cable like this for the job, and never had a problem.   Am i missing something obvious?

+1
I only carry this 1/8"-1/4" cable for all of my iPod/laptop needs.  On most consoles I go in the line inputs, on real consoles with only xlr in, I go in the insert returns.  When I'm on a Yamaha digital or something with no 1/4", I carry a few pairs of 1/4"-f to xlr-m adapters.  Doing this there is still the possibilty of voltage hitting the outputs of the iPod, but it's pretty well reduced. 

I would be skeptical of using tiny transformers for a line level signal.  It's really pretty easy to overload most transformers, and I would hesitate to put anything short of a $50/ea IL19 on any line level signal that is supposed to produce good, full range sound.

thomas d.
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Luke Robinson

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Re: 1/8" to XLR
« Reply #13 on: February 08, 2011, 09:56:01 pm »

Rapco makes a really small and clever little DI I like to use for this, it is in mono but it is cheap and small.

http://www.markertek.com/Audio-Equipment/Audio-Interface/Computer-Audio-Interface/Rapco/LTIBLOX.xhtml
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John Livings

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Re: 1/8" to XLR
« Reply #14 on: February 08, 2011, 11:12:07 pm »

I have a setup using a Yamaha MG-102c [http://usa.yamaha.com/products/live_sound/mixers/analog-mixers/mg_series_cx_models/mg82cx/?mode=model]

and a Bose Sound Dock with a 3.5 mm jack. (Aux Input)

I want to use the "Stereo Out L and R" of the MG 102,  The manual calls the 1/4" jacks "Balanced"

Should I use TRS to 3.5mm or TS to 3.5mm or does it matter?

I am putting together a Practice Rig and needed 4 Mic Pre's, the IPod and ?

Just trying to keep everything easy to transport and set up.

In case you don't already know; the Bose Is Loud (For it's size) but sounds Less than ideal, but it's a trade off

Regards,  John
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Dan Richardson

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Re: 1/8" to XLR
« Reply #15 on: February 08, 2011, 11:31:21 pm »

Oh yeah, I've had one of those little Rapco boxes for years.
It's my goto box for getting audio from the random laptop
set up next to the video projector in whatever situation.

And yeah, tiny transformers don't get there.

And yeah, the two desks I'm most liable to see are the Yamaha M7C and the LS9,
neither of which has inserts or 1/4" inputs without optional cards.
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