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Church and H.O.W. Forums for HOW Sound and AV - Your Displayed Name Must Be Your Real Full Name To Post In The Church and HOW Forums => Church Sound => Topic started by: Karl Stringer on March 19, 2012, 01:22:25 pm

Title: laptop 3.5mm out to XLR
Post by: Karl Stringer on March 19, 2012, 01:22:25 pm
Hi
I have tried google and failed miserably, so here goes!
I need to make up a cable that will take the stereo output from the 3.5mm headphone jack of our Priest's laptop and put it into a single channel input.
The laptop can't be moved - he needs it near the pulpit to see what is on the screen & that is where the VGA cable is that feeds the projector.
There is a single (balanced) XLR input available to do this with.
I know that I could run two unbalanced XLRs to the mix processor (Allen & heath idr4 system) but it is a hard wired system and installing another long run of cable would be a major headache.
So, how do I do it? the wiring is all balanced. (legacy cabling as we have now gone to wireless mics).
Not the best solution I grant you, but its all we have.
Thank you
Title: Re: laptop 3.5mm out to XLR
Post by: TJ (Tom) Cornish on March 19, 2012, 01:26:40 pm
Hi
I have tried google and failed miserably, so here goes!
I need to make up a cable that will take the stereo output from the 3.5mm headphone jack of our Priest's laptop and put it into a single channel input.
The laptop can't be moved - he needs it near the pulpit to see what is on the screen & that is where the VGA cable is that feeds the projector.
There is a single (balanced) XLR input available to do this with.
I know that I could run two unbalanced XLRs to the mix processor (Allen & heath idr4 system) but it is a hard wired system and installing another long run of cable would be a major headache.
So, how do I do it? the wiring is all balanced. (legacy cabling as we have now gone to wireless mics).
Not the best solution I grant you, but its all we have.
Thank you
Radial ProAV1:
http://www.radialeng.com/r2011/proav.php

or Whirlwind PC-DI:
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/direct-boxes/pcdi
Title: Re: laptop 3.5mm out to XLR
Post by: Tom Young on March 19, 2012, 02:45:14 pm
Radial ProAV1:
http://www.radialeng.com/r2011/proav.php

or Whirlwind PC-DI:
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/direct-boxes/pcdi

+1

Both devices are designed and built very well.

The Radial has (only) a mono output, which may come back and bite you when you need stereo.

The Whirlwind has a switch which sums L&R into mono but otherwise is stereo.
Title: Re: laptop 3.5mm out to XLR
Post by: Mac Kerr on March 19, 2012, 03:03:16 pm
Radial ProAV1:
http://www.radialeng.com/r2011/proav.php

or Whirlwind PC-DI:
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/direct-boxes/pcdi

For a hell of a lot less money than a PCDI you can get a Peavey USB audio adapter (http://www.bhphotovideo.com/c/product/759075-REG/Peavey_USB_P_USB_P_USB_Direct.html) that will likely have better audio than the headphone output of the computer. It will need you to select the USB device as the audio ooutput on the computer, but it does not require a driver.

Mac
Title: Re: laptop 3.5mm out to XLR
Post by: Karl Stringer on March 19, 2012, 05:17:56 pm
Thanks for the suggestions.
I found this suggestion - please pick holes in it!

At the XLR end connect pins 1&3 together (creating an unbalanced cable). And connect to ground from both L&R feed.
Connect pin 2 to the L&R combined BUT place a 10K resistor (in line) on Each before the cables are joined to pin 2.
Thus creating a sum of the stereo without the danger of overloading the output amp.

Have to be handy with a soldering iron and some heat shrink but that's not a problem.

Title: Re: laptop 3.5mm out to XLR
Post by: TJ (Tom) Cornish on March 19, 2012, 05:31:49 pm
Thanks for the suggestions.
I found this suggestion - please pick holes in it!

At the XLR end connect pins 1&3 together (creating an unbalanced cable). And connect to ground from both L&R feed.
Connect pin 2 to the L&R combined BUT place a 10K resistor (in line) on Each before the cables are joined to pin 2.
Thus creating a sum of the stereo without the danger of overloading the output amp.

Have to be handy with a soldering iron and some heat shrink but that's not a problem.
It's unbalanced.  Game over.
Title: Re: laptop 3.5mm out to XLR
Post by: Mac Kerr on March 19, 2012, 05:33:01 pm
Thanks for the suggestions.
I found this suggestion - please pick holes in it!

At the XLR end connect pins 1&3 together (creating an unbalanced cable). And connect to ground from both L&R feed.
Connect pin 2 to the L&R combined BUT place a 10K resistor (in line) on Each before the cables are joined to pin 2.
Thus creating a sum of the stereo without the danger of overloading the output amp.

Have to be handy with a soldering iron and some heat shrink but that's not a problem.

If the actual cable run from the pulpit to the console input is more than a few feet I would not run it unbalanced like that. For $50 get the Peavey and push the mono button. Have a real line level balanced feed on an XLR connector, as well as the possibility to use it as a stereo output in different circumstances. In addition will not be using the headphone amp in the laptop which is often the weak link in the audio chain, nor the 1/8" connector, the other weak link.

Mac
Title: Re: laptop 3.5mm out to XLR
Post by: Karl Stringer on March 19, 2012, 06:10:42 pm
Again thanks for the replies.
As i have just realised, Your suggestions will also stop the laptop being blown up if someone accidentally turns phantom on.

That peavey box looks ideal.

Out of interest I also found a discussion here
http://forums.prosoundweb.com/index.php?topic=287.0
Title: Re: laptop 3.5mm out to XLR
Post by: John Penkala on March 21, 2012, 06:57:25 am
Hi
I have tried google and failed miserably, so here goes!
I need to make up a cable that will take the stereo output from the 3.5mm headphone jack of our Priest's laptop and put it into a single channel input.
The laptop can't be moved - he needs it near the pulpit to see what is on the screen & that is where the VGA cable is that feeds the projector.
There is a single (balanced) XLR input available to do this with.
I know that I could run two unbalanced XLRs to the mix processor (Allen & heath idr4 system) but it is a hard wired system and installing another long run of cable would be a major headache.
So, how do I do it? the wiring is all balanced. (legacy cabling as we have now gone to wireless mics).
Not the best solution I grant you, but its all we have.
Thank you

Carl,
        I carry 3 of these in my bag for computer audio on corporate shows when a mono signal is acceptable.

http://www.rapcohorizon.com/p-379-ltiglblox.aspx

Title: Re: laptop 3.5mm out to XLR
Post by: Kent Thompson on March 21, 2012, 12:40:09 pm
I have both a USB preamp and one of the Radial av DI boxes. I use them both on and off. The USB preamp is nice because it allows me to capture audio into my laptop as well. In other words there are more uses for it than just sending signal out to the system but, if someone I don't know is bringing their laptop in to play music through my system getting them to plug in my USB device might cause some concerns(even though I know it won't cause any issues) hence the reason I also have a DI. I would chose the USB device for versatility. The DI if I am connecting to several different and unknown devices.
Title: Re: laptop 3.5mm out to XLR
Post by: Jonathan Johnson on March 24, 2012, 01:15:46 am
If you don't go the USB interface route, best to use a DI box with summing circuitry to mix the L & R into a mono signal. Don't want to use a Y-cable; 93% of the time it will work, 5% of the time you'll end up with weird cancellations, and 2% of the time you could damage the output of the laptop's headphone jack.