Serious Humming/Feedback

Discussion in 'Mixing & Song Critique' started by Scott P, Dec 13, 2016.

  • AT5047

    The New AT5047 Premier Studio Microphone Purity Transformed

  1. Scott P

    Scott P Member

    Joined:
    Dec 13, 2016
    Location:
    Newport, RI
    I recently purchased a brand new Numark Mixdeck Express midi controller. I connected it the other night at a gig to my QSC K12 speakers using XLR cables. On the rear of the controller are 3 XLR outputs that say BALANCED. I connected regular XLR cables (microphone cable) and ran it to the left and right speakers separately. I then tried to power up the speakers and they would not turn on. Thinking it was a bad power source I plugged them into another outlet. Finally once the speaker turned on the sound that came through was an extremely loud hum!!! I got nervous and shut the power off immediately to the speaker. The problem wasn't the cable unless it was an UNBALANCED cable and I didn't know about it. I ended up hooking up a backup controller and the cables were fine. Do you think the Numark midi controller can only use BALANCED XLR cables as outputs? The weird thing is the speakers not turning on?????? They did however once I hooked them up to my backup controller. NOTE- I did test the brand new midi controller at home but with another set of speakers and cables. Any help would be greatly apprciated.
     
  2. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

    Joined:
    Feb 21, 2013
    Location:
    Quebec, Canada
    Home Page:
    You should use an xlr to xlr balanced cable between the mixer and the speaker and also make sure you have the input switch to line and not mic.
    I don't know if I have to say it.. but the mixer master volume should be down and the mixer powered up before you power up the speaker which should also have the power down before you start them.
    put some signal through the mixer and put the master volume to unity gain ( the bold bar below the top ) do the same with the chanel volume and adjust the gain so it doesn't touch the red leds. Then turn up the speaker input slowly.
    If you still have hums, it may come from bad AC wiring and/or if you have it connected to a computer it may be it's power or on a different phase.. anyway.. do the first steps and come back with the results. we will deal with what ever happens ;)
     
  3. dvdhawk

    dvdhawk Well-Known Member

    Joined:
    Dec 18, 2008
    Location:
    Western Pennsylvania, USA
    It's never a bad idea to check your mic cables to make sure all 3 conductors are correct, but the scenario you are describing has me more concerned about the integrity of your electrical connections than the audio connections. I feel like these are 2 unrelated symptoms. If the K12s would not turn on, (no power, no pilot light), then the speaker isn't getting power. There's really nothing I can think of you could do incorrectly with the audio connections that would keep the speaker from powering up.
     
    pcrecord likes this.
  4. dvdhawk

    dvdhawk Well-Known Member

    Joined:
    Dec 18, 2008
    Location:
    Western Pennsylvania, USA
    Have you been able to recreate the problem?
    Did it hum regardless of which input source was selected?
    Is it possible you're using a turntable with a magnetic cartridge that wasn't grounded properly?
     

Share This Page