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  1. #1
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    Hum Issue (Long Post)

    Hi All -I stumbled onto this board via Google. I really hope someone hear can help guide me to a probable solution.

    Here is my situation: About 6 months ago I began the process of moving all video recording equipment and computers/monitors, etc. away from the sound board at our church into a back room about 50 feet away from the 32 Track Board and all audio equipment.

    Prior to this move the audio was coming from a raw line out the board about 4 feet away and into the NewTek SX-84. Soon after I found a noise in the audio and thought I could just tweak it out in editing but of course once its recorded its darn hard to minimize/remove it but so much without deadening the original intended audio. Anyway I changed some cheap RCA wiring to what I thought was a better cable, PYTHON 75ft. rca and the problem was still the same.

    At this point I'm wondering if the humming is from the distance or possibly a ground loop that a hum eliminator may correct or perhaps a balanced audio cable issue.

    The audio is being sent from the mixer board to the switcher and captured along with video for broadcast. The video is fine its just the audio thats screwed.

    Any insight will be greatly appreaciated.

  2. #2
    well if you are running a 75' rca cord what you have is a 75' antenna. Any run that long should be balanced by all means, secondly you are now dealing with two different circuits one at each end of the signal providing power to the devices at either end. That means two grounds. That can also be a problem in audio if the service is not isolated. What are the input and output configurations of the gear you have hooked up? you might try a di box at the scource end and lift the ground.

  3. #3
    I suggest using the balanced lines on BOB.
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

  4. #4
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    Quote
    Quote: tonsofpcs
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    I suggest using the balanced lines on BOB.
    Sorry I'm not sure what you mean by BOB? Thanks

  5. #5
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    Quote
    Quote: peter miller
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    well if you are running a 75' rca cord what you have is a 75' antenna. Any run that long should be balanced by all means, secondly you are now dealing with two different circuits one at each end of the signal providing power to the devices at either end. That means two grounds. That can also be a problem in audio if the service is not isolated. What are the input and output configurations of the gear you have hooked up? you might try a di box at the scource end and lift the ground.
    Thanks for the reply - on top of the move many of the wires are being ran not far from AC units etc so the opportunity for interference is great.

    The output is coming off of the board running to the back into another board from the NEWTEK system and then into the computer used for capture and editing. The problem is not the NEWTEK board as even running the cables directly into another TV (RCA/PHONO) or into a signal splitter or anything rally still has the same "hum" some a little louder than others but still noticable clearly in the capture and live audio monitoring.

    Again before the move, there was NO hum at all. Someone suggested it may be something called "dirty a/c" so I ran an extension back to the power supply it was origianlly located and still got the hum so if that really was an option it wasn't the solution.

    At this point I want to try either the DI Box or a HUM ELIMINATOR solution like from ebtech. Any thoughts?

    thanks again for the suggestions.

  6. #6
    Well, making the run balanced any way you have to make it happen would be the first and formost thing to do. I'm not a big fan of hum eliminators as they are just like trying to paint over something instead of removing it completely. As far as dirty power pretty much all power is dirty to some degree as far as ac line noise, Chances are you are picking up inductance along your giant antenna somewhere , also to clarify is it a 60hz hum or is it some sort of interference? Also if you are running any kind of line signal along side ac power than there is a high probability that you will get inductance. Most of all what exactly are the inputs and outputs we are dealing with on these two units being hooked together, and also are you possibly hooking a +4 to a -10 input or vice versa and so on?

  7. #7
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    I believe it is a 60hz hum. Okay here are the output/input variations

    At first it was coming out of the board on a single 1/4" Plug split into a dual RCA which took the sound to the back for capturing and splitting.

    Thinking that was the source perhaps, moved the RCA 75' cable to an output from Denon Deck (located in the front where all audio mixing and capturing goes on for cd's, cassettes and congregation). This then ran to the back for video capturing and splitting. FYI - there is no hum in the finished product for audio cassettes or CD or heard by congregation only when ran to back meeting interference).

    Either way the hum was still there.

  8. #8
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    Bought this last night from SamAsh, after asking the guy there exactly how to hook it up, there was no more hum BUT THERE WAS NO AUDIO EITHER

    1) Took 1/4" plug from mixer, plugged it into the IN 1/4" on the Whirlwind Box.
    2) From the output of the Whirlwind Box, placed XLR cable in then split from 1/4" to dual RCA to setup
    3) no audio whatsoever, adjusted the Ground Lift and attenuation options and nothing

    The guy from SamAsh said NOT to put anything into the 1/4" OUT slot, just the 1/4" IN slot and then the OUTPUT (XLR).

    Any thoughts?


    Thanks

  9. #9
    Well a little confused how you turned a balanced XLR signal into RCA again there, but on the DI there is also a 40db pad, make sure that is not on 40db or 20db and that it is on 0db that would be my guess

  10. #10
    Quote
    Quote: zicman
    View Post
    Sorry I'm not sure what you mean by BOB? Thanks
    BOB is what NewTek calls the SX84 Break-Out-Box
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

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