Loud hum when sending a line out to the pa

Discussion in 'Amps and Cabs [BG]' started by Gabu, Mar 9, 2002.

  1. Gabu


    Jan 2, 2001
    Woodland Hills, CA
    For yesterday's practice I left my Carvin rig at home and took my SWR Bass 350 amp with a 210 cab. I ran it at about 66% gain and 66% master volume, and I ran a line out to the PA. I got a very loud hum coming through the pa.

    When I run the same setup and turn the the amp up in my garage, I can hear a hum too. But it's not nearly as loud. This is the first time I have used this smaller rig so I don't have any past experience to compare the performance too. Can you guys offer me some advice on what might be producing this, and how to troubleshoot or resolve this?

  2. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    getting warmer
    ground loop maybe? Or the pre tube might be shot.
  3. cb56


    Jul 2, 2000
    Central Illinois
    A couple of places we play have this problem. If the ground lift on your amp doesn't help try running an extention cord over to wher your mixing board and amps are plugged in so you are plugging your bass amp into the same circuit that the pa, board and amps are plugged into. This cures the problem every time for me.
  4. Gabu


    Jan 2, 2001
    Woodland Hills, CA
    Thanks for the replies. :) I will try plugging the two into the same outlet at the studio.
  5. Hey Gabu,

    That's just a ground loop. cb56's advice should work. If not you could make up a short XLR adaptor with pin one (the shield) not connected on the male connector. If it's doing it with the 1/4 line out it's a bigger problem because you can't lift the shield on an unbalanced line. Feel free to PM or email me if you continue to have problems.