HELP! Grounding issue is driving me nuts

Discussion in 'Amps and Cabs [BG]' started by Brandon Johns, May 1, 2019.

  1. hey guys, I'm having some issues with my bass rig as far as grounding goes.
    I run a full mark bass set up everything is rack mounted on the head end. when i plug both my in ear monitors and plug in the xlr into the direct out i get a wicked 60 cycle buzz through the pa (doesn't come through the cab) hit the ground lift and it gets worse I've tried to rewire everything in the back and no change... switch the xlr to my other head... no change... Im at a loss any ideas what could be causing it? any ideas on a fix?

    Heres my set up
    Furman power conditioner
    Shure slx4 In ear monitors
    Shure PSM 300 wireless guitar
    Korg Pitch-black tuner
    Alesis 3630 Compressor
    2- Mark Bass Little Mark Tube 800 (each powers a different cab)
    Mark Bass 4-10
    Mark Bass 15 57412514034__BAE6E8D5-59C9-4193-B8C8-9FACE6CB8994.JPG IMG_0942.jpg
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Does it go away when you switch off your IEM transmitter?
  3. i had the issue once when we were opening for a national act i pulled the send out of the IEM system and the buzz went away however this last weekend it did not we ending up not using the xlr and just mic'd it
  4. Mingo Sanders

    Mingo Sanders

    Mar 11, 2008
    Austin, TX
    The only long distance suggestion I have is to disconnect devices one at a time to see if you can isolate the problem. In the alternative, take the whole thing apart (sorry) and connect it one device at a time to determine which connection is causing the problem. Be methodical and change strictly one thing at a time. Also, make sure each individual link in the chain works normally with known working gear. Good luck!
  5. i forgot to add this in the original post
    at our show on saturday i powered everything in the rack down except for the power conditioner and there was no change even powered off

    but that's what i planned on doing i just wasn't sure if someone has had similar issues and what they did to fix it
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Is it possible that the problem was not your gear but something external to your rack?
  7. I guess it could be a possibility... this is the first rack I have put together I did not use rack isolators on the rails... I’m not sure if that would make a difference
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I'm talking about the PA or input wiring to the PA.
    Redbrangus likes this.
  9. jw23mind

    jw23mind Supporting Member

    Jan 16, 2017
    Reading MA
    Possible that the headroom and galvanic isolation of transformer-based DI might work where the (presumably) active-DI does not.
  10. It’s because of the 15” & 4x10” cabs. The setup makes interference through the ethers with the beliefs of the TBers and causes static buzz. :):):)

    No, seriously I had such a thing and it was one 1/4” plug not fully plugged in back in the rack.
  11. Former Rogues

    Former Rogues

    Sep 22, 2016
    I am not a rack guy, so don't take my advice over others. The suggestion to isolate components is probably the best, to identify exactly where the problem stems from.
    Are you using isolated power supplies/power conditioner?
    This was a problem for my pedal rig, easily solved by investing in a quality, albeit more costly power supply.
    Lastly, and correct me if I am wrong fof suggesting this, but could you add a noise gate in the signal chain? I don't know if that would solve the problem, but it could be a cheap and quick fix until you can isolate the problem.
  12. Andyman001

    Andyman001 moderation must be taken with a grain of salt

    Feb 11, 2010
    S/E Idaho
    where are the DI & monitor feeds coming from? how are you running to both heads? FX loop or in the Inst. input?
  13. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    This could easily be caused by the PA being on a different electrical circuit from your rig. Try it at home. If it happens not at home but only at the gig, run your rack power to the same outlets as the PA.
  14. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    To test, ground lift your whole rack. Be careful and I don’t suggest playing that way but often the grounds are tied through the chassis and lifting a single unit won’t do anything.

    Sounds like the PA power and rig power aren’t wired the same.
  15. basscooker

    basscooker Commercial User

    Apr 11, 2010
    Northern KY
    Cab fan, hobbyist
    I as well suspect something related to power supply.
    Lol did the guy have the phantom power on your channel?
    BasturdBlaster likes this.
  16. No fluorescent or corkscrew lamps nearby?
    basscooker and BasturdBlaster like this.
  17. Reedt2000

    Reedt2000 Supporting Member

    Apr 26, 2017
    Central New Jersey
    This is exactly what I thought.

    Is this the only time it's happened?
    BasturdBlaster likes this.
  18. Wasnex


    Dec 25, 2011
    BasturdBlaster likes this.
  19. Red Planet

    Red Planet Inactive

    May 29, 2005
    I'm cranky in my old age.
    I had this issue with an Ampeg SVT 1000 and DI to FOH and ended up making a short XLR cable with a hard wired ground lift on the amp end of the cable and the problem stopped. This was per Jerrold Tiers (Ampegs Engineer) who suggested many of these amps with an electronic balanced out aren't as good as a transformer balanced out. Of course this did not fix the actual problem but it eliminated the hum.
    Reedt2000 and Wasnex like this.
  20. yes i run both heads ( i run no fx in my rig just a compressor) the bottom head powers the 15 and the top powers the 4-10 i split my signal coming out of my wireless then into the tuner into the compressor then into the head.