Monitor/FOH Buzz

Discussion in 'Live Sound' started by allenk, Oct 9, 2006.

  1. allenk

    allenk Guest

    A club I play at regularly has there lights on a dimmer switch. It created a buzz when we sound checked, but when the band starts they turned them off and the buzz is gone. Now they have put in new lights and they have to be on all the time and we get a bad buzz. The owner says were the only band who gets the buzz. We dont have a problem anywhere else. Is there any way to get rid of this? tips, tricks. I have tried everything I can think of. Any help would be greatly appreciated. :roll:
  2. Zoro

    Zoro Guest

    Have you checked for any ground?
    Like an Amp that the guitar player has or the bass player?
    Do they use any extension cords that aren't grounded?

    Check for that third Ground Pin that some people mistankenly brake down in their Amps/equipment to fit into a cheap extension cord.

    Hope it helps.
  3. allenk

    allenk Guest

    Thanx for the response.
    Everyone is plugging in on the stage outlets, Im pretty sure nobody is using a ground lift, but I will check that when we setup this weekend.
    Only thing that seems to help is running ext. cords to the other side of the room from the light circuit we still have buzz though. We went thru checking all the cables that could be causing it. I played in a band a few years back that used there own distro and tied in at the fuse box. We never had any problems ever.. but i would not no how to wire it up. I do not see how were the only band with this problem. Its gone when they turn off the lights but that is not an option now. :cry:
  4. moonbaby

    moonbaby Mmmmmm Moderator

    Feb 23, 2005
    You say in the title of your post that this is coming through the FOH and monitors, correct? Are you using a snake that is running between the FOH rig and the monitor rig? Can you physically see the electrical conduits that are feeding power around the venue?
    My take is either that:
    A) The lighting has a dimmer system that is cheap and crappy, emitting RFI. This is especially true if they are using those wall-type dimmers your dad gets from Home Depot to work on the dining room chandalier, or:

    B) You are plugging part of the PA rig into power at the stage area, then connecting the audio to a FOH position that has the rest of the PA getting its power from a different leg in the club: a "ground loop" is the result.
    You can fix this by running the AC power to feed the FOH position from the same leg that's feeding the stage, using a good, grounded heavy-duty extension cord. You already seem to know that you don't break the ground at the plug.
    Check out your rig and take it from there. If it IS RFI from the dimmers, you are in a tight spot.All you can really do is what you're doing now...move the AC cords away from the wall carrying the AC to the lights.
  5. allenk

    allenk Guest

    Buzz is in both, a little worse thru the monitors but not by much. We have a new allen and heath mix wizard we setup in the back of the room. It is about 60 feet from the stage in a rectangular room. We run a snake from there with our monitor returns. We do not have a seperate monitor board. We use the allen and heath. I think you can see the conduit, not for sure though. I believe the owner knows where the circuits go if they are in the wall.
    I think that the mixer is plugged in to a different circuit than the power amps and our stage gear.
    So we should run our mixer power down to the stage with everything else,
    I did not think of that one damn it. That could very well fix our problem.
    But if not.. what kind of dimmer switch should I look for or look out for?
    Thank you very much for your help moonbaby 8) Kevin
  6. sheet

    sheet Well-Known Member

    May 28, 2003
    Kansas City, KS
    Home Page:
    Here are things to look for as well.

    Investigate the AC:
    Make sure that no kitchen equipment is on the same leg, has the same ground, as you will have some EMF backfeeding on the ground when the motors cycle.
    Make sure that neon ballasts are not plugged into the same circuit, and that if they are dimmed, they are the dimmable type. I have seen many people try to dim those old Budweiser, etc things, and it ain't pretty for sound.
    Sounds like the lighting is on the same leg. Don't use that circuit.
    Make sure that the band and sound AC source is the same leg.
    There are only two or three really good analog dimmers to consider. They are very expensive and mostly used in low-noise critical environments. Digital dimmers are cool for clubs, and will actually prolong lamp life. They aren't as expensive as their analog counterparts.

    I used to hear all the time, "You are the ONLY guy that complains about my AC." Yeah, well one club burned to the ground because he wouldn't listen and hire an electrician to sort out his mess.
  7. allenk

    allenk Guest

    Thanks for the input, I think Im starting to get a good grasp of whats happening. You could be right...the kitchen/bar appliances might be on the same leg as our mixer. I will be checking that now as well.
    Thanks again, Kevin
  8. allenk

    allenk Guest

    If all stage and pa gear are on the same leg, what size of breaker should be in place to carry the load? Is their a standard on this or recommendation?
  9. sheet

    sheet Well-Known Member

    May 28, 2003
    Kansas City, KS
    Home Page:
    Whatever the draw is.

    If this were a serious venue, you would have three-phase power. But this is rare for little clubs.

    Is this an installed system?

    1. Each power amp should have it's own 15A-30A breaker (whatever is required. Remember that you don't get max power output if you are choking the amp.) You could have a pair of amps on one 60A, but I prefer to have power amps on discrete breakers.
    2. The stage should have a couple of 20A circuits for backline, racks, etc. Same thing holds true for instrument amps. Choking the power means distortion, less output, etc.

Share This Page