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Hum through the PA....

Discussion in 'Amps and Cabs [BG]' started by string_dean, Mar 18, 2004.

  1. We were using a new PA for the first time Saturday night, and I ran direct out from the back of my amp to the board. There was a noticable hum through the mains, so I ran direct out from a Sansamp Bass Driver. Same noise in the mains, even after switching the ground/phantom switch on the SABDDI.

    We were running late, so I just stuck a mike in front of the speaker, as there was no buzz coming through the amp. My question is, does the ground lift on the amp and the SABDDI work together? If the ground on the amp had not been changed, would there still be a hum? Any help would be appreciated.
  2. Petebass


    Dec 22, 2002
    QLD Australia
    It was probably just a faulty lead. That the first thing I change if I get a hum that the ground lift can't fix. If that doesn't work, I try turning off the phantom power at that channel.
  3. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Most solid state DI's aren't truly isolated. The only way to get perfect isolation is with a transformer. Try perusing some of the DI-related technical info on www.jensen-transformers.com.
  4. A quick and dirty fix is to open up the XLR jack on ONE end and snip pin one which physically breaks the ground connection on one end. If that doesn't fix it, your mic cable/snake is picking up the noise itself.
  5. Thanks for the input! You can always learn here at TB!
  6. Arranger


    Mar 9, 2003
    Was your XLR out pre or post EQ? If it was post and your preamp signal was too low, the mixer could just be amplifying a weak signal. Then you could just turn up your amp gain and turn the board down.

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