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Advice needed - bursts of noise, ungrounded outlet

Discussion in 'Amps and Cabs [BG]' started by Magman, Aug 12, 2007.


  1. Hi -
    Moved to new rehersal room complex.

    Started getting bursts of noise (like RF noise, or even cell phone) though rig - especially prominent with high gain overdrive sounds, and when a signal is going though the rig (ie when nothing being played, normal hiss). Have several pedals/ rack units and a large power amp (yorkville 3400....2k watts).

    Intensive troubleshooting did not pin point any particular cord/power strip/bass etc as the problem. Never had problems like this before with any of the gear.

    Big clue: one power strip (not mine) has a 'grounded when lit' grounding light. It is OFF most the time (bad!). However, when the noise 'pulses' occur when using the amp the light flashes in time with them. The noise is intermittent. I don't know why a signal makes the ground appear and dissappear quickly, nor why the variable ground creates audible noise.
    To reiterate -- the noise seems directly related to the presence/absence of ground on the power supply as indicated by the powerstrip. A signal through the amp seems to activate the ground in a pattern of noisy on/off ground connection.

    I tested the entire rig with a much smaller combo amp... the noise still occurs, but much less often. Something about the yorkville amp seems very sensitive to the problem, whatever it is.

    I'm going to get an outlet grounding tester for double confirmation of the ground issue at the socket.

    - Are these symptoms typical of having a bad ground connection?

    - What are the risks of running from an outlet with bad grounding?

    - If I confirm the power is bad, I will call the management. Any tips on handling the situation?

    - Any techniques for cleaning up the power supply that are within my control?

    thanks MM
     
  2. John Wentzien

    John Wentzien

    Jun 25, 2007
    Elberta, AL
    Artist:TC Electronic RH450 bass system (original test-pilot)
    A power conditioner of some sort might help. There are some simple plug-in gadgets that can tell you if the outlets are wired properly and grounded. You can get one at the hardware store.
     
  3. Steve

    Steve

    Aug 10, 2001
    Take a good look at that power strip as well. It may very well be the cause.
     
  4. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Yes
    Electrocution is at the top of the list.

    Be prepared to find another room. He probably cares less about your business than what it might cost to fix.

    Not unless you're an electrician.
     
  5. Does a GFI (ground fault interupter) protector provide electrocution protection in these situations?


     
  6. seamonkey

    seamonkey

    Aug 6, 2004
    Consult a licensed electrician - but AFAIK - GFI only helps if the outlet is properly wired and grounded. It can't reliably check for a "Ground Fault" if the outlet isn't wired correctly.
     
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    It does if the wiring is correct. Catch 22: If the wiring is wrong a GFCI may not work, if the wiring is correct a GFCI probably isn't required.
     

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