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  1. #1
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    PC to mic jack (XLR)

    I have been given the opportunity to do sound at the local school's varsity softball games. However I am having a problem hooking into their sound system. I run the music from my PC. The sound system is in a rack which I cannot access cables in the back. The only input available is an XLR mic jack. So my goal is to from the headphone jack on my laptop to the mic XLR input jack.

    Some questions:

    - Is this type of connection workable? My initial attempt resulted in a very low signal with awful sound.

    - What type of cable setup should I be using? This one (with a 1/4 to 1/8 adapter at the end for the PC)?

    Thanks,

    Dave

  2. #2
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    Quote: DutchDave
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    I have been given the opportunity to do sound at the local school's varsity softball games. However I am having a problem hooking into their sound system. I run the music from my PC. The sound system is in a rack which I cannot access cables in the back. The only input available is an XLR mic jack. So my goal is to from the headphone jack on my laptop to the mic XLR input jack.

    Some questions:

    - Is this type of connection workable? My initial attempt resulted in a very low signal with awful sound.
    You'll likely need to keep your output low and run it through an attenuator (40-50dB should be good).

    - What type of cable setup should I be using? This one (with a 1/4 to 1/8 adapter at the end for the PC)?
    Nope, that's for balanced outputs. Your PC out is stereo unbal, the mic ins are mono balanced. You'll want to wire your 1/8" plug (TRS for Tip/Ring/Sleeve) to two XLRs like this:
    T to 2 on XLR-1
    R to 2 on XLR-2
    S to 1 and 3 on both XLRs

    Remember, don't plug this directly in, run it through a line-to-mic attenuator.
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

  3. #3
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    Hi Eric - Thanks for the reply.

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    Quote: tonsofpcs
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    Nope, that's for balanced outputs. Your PC out is stereo unbal, the mic ins are mono balanced. You'll want to wire your 1/8" plug (TRS for Tip/Ring/Sleeve) to two XLRs like this:
    T to 2 on XLR-1
    R to 2 on XLR-2
    S to 1 and 3 on both XLRs
    There is only one mic XLR input available. Is there a way to wire it up to one XLR?

    Quote
    Quote: tonsofpcs
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    Remember, don't plug this directly in, run it through a line-to-mic attenuator.
    I don't have a line-to-mic attenuator but I do have access to a DB-1 direct box. Will that work as well?

    Dave

  4. #4
    A direct box will help in that it will change the signal to a balanced line, but it'll only do one channel..and if you are right in the booth with the equipment you might not need it, ther are no RCA's open? Is there a CD player you could unplug while you are there?? Are you running in stereo (like is there actual pan/separation in the output and speakers) or mono? THey do make PC DI's (WHirlwind) and I'm sure f you go to Fullcompass.com, sweetwater.com, etc they'll have some solutions for you.

  5. #5
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    Quote
    Quote: Bassred
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    ther are no RCA's open? Is there a CD player you could unplug while you are there?? Are you running in stereo (like is there actual pan/separation in the output and speakers) or mono?
    That's my issue. The radio and cd player are in a rack that gets locked up in a metal "cage". You open the front door with a key and do not have access to the cables in the rear.

    Yes, the output will end up being mono. The output is stereo (like the CD player) but there are three speakers. One pointing to the field and the other two pointing towards each dugout. I'm pretty sure it's mono.

    I'm hoping to get this working by Monday (their first home double header). I can get access to the unit tomorrow afternoon. I may just bring some tools and pull the CD player or receiver (by unscrewing them from the rack) and use those RCA jacks. The school may not be happy with me but at least I may get it working.

    Dave

  6. #6
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    Using the mixer board at church today I was able to get quality sound from an ipod to an XLR input jack. I'm sure there may be other combinations that worked, but this is what I had (in the order of connection from ipod to XLR jack.)

    - 1/8 to 1/4 stereo adapter
    - mono 1/4 inch cable
    - DB-1 direct box
    - XLR to 1/4" TRS Connector (as illustrated here)

    I will test it out later today at the softball field. I'll let you know how it goes.

    Dave

  7. #7
    If it's only one input then yes, make that cable, but with a mini (1/8") mono instead of a 1/4" mono. You may be able to connect them directly, but you would have to output a very low level from your computer (as low as possible while being above 0 is a good start point) and turn down the input on the amp, then slowly bring the input level up. I strongly recommend against this, but it may be workable.

    You say there is a rack that you cannot get to the back of, but you can get to the front of. Doesn't anyone have a key for the back of it? I'd think that the best way to go about this is find the master house mixer and/or amp and plug directly in.
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

  8. #8
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    Quote
    Quote: tonsofpcs
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    You say there is a rack that you cannot get to the back of, but you can get to the front of. Doesn't anyone have a key for the back of it? I'd think that the best way to go about this is find the master house mixer and/or amp and plug directly in.
    I'll get another look at the rack in a few hours. Its like a steel cube with a front door mounted to the wall. I assume they got access to the cables by unscrewing the particular device (CD, tuner, etc.) and pulling it out.

    I have an email into one of the school employees who I guess works with this stuff. He was on vacation last week. I'm hoping we can connect sometime this week and come up wit a better way to hook into the system.

    Off topic - I see you are from Oswego. My great, great, great grandfather owned the Goble Dry Docks there from the mid 1800's till around 1900.

    Dave

  9. #9
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    It worked

    It worked. Although I did have to crank up the gain on the mic input and the master level.

    Dave

  10. #10

    stereo line to mono balanced mic

    I haven't been on this board long enough to know how to attach a picture, but you may be able to deal with the following verbal description. Glad it worked for you, but you shouldn't have had to turn up the mic level so high - that's a red flag. (Assuming it really is a mic input; lots of line inputs are wired to 3-pin connectors too.)

    First: never parallel the left and right headphone output channels. True, both channels combine to drive the output, but they also drive each other, and they fight. This usually leads to distortion and often leads to damage.

    Second: a headphone output is at least 100 times higher than the mic input is expecting. And it expects to see something balanced.

    So you need a circuit that combines the channels without shorting them together, reduces the overall output by 100X, and converts from unbalanced to balanced.

    This takes a bit of construction, but if you're up to it, try this: pick up two 1K-ohm resistors and a 20-ohm resistor. The 20-ohm one goes across the balanced mic input, pins 2 and 3. From pin 2, two 1K resistors go to the left and right outputs if the computer (tip and ring). Connect pins 1 and 3 and the computer ground (sleeve) together via the wire shield.

    BTW, do you get a loud pop when you connect and disconnect the computer? If so, the mic input may have phantom DC power on it. In that case the only good way to do this is to buy a true transformer-isolated adapter. DC feeding backwards into the computer will eventually ruin your sound card.

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