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Re: Hum/Buzz

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Az Barber

(A)

In Reply to: Re: Hum/Buzz posted by oldroadie on February 9, 2005 at 14:39:07:

Yes, there are dimmers. What will filter out the dimmer noise?
Thanks!
Az

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Re: Hum/Buzz - oldroadie 14:45:52 02/09/05 (13)
Nothing known to mankind. Dimmers can be made to NOT do this, they are special (expensive).
Move the audio circuits to a leg of AC not using the dimmers, or some dimmers can be shut off at the breaker panel.

Tom
- Re: Hum/Buzz - Az Barber 15:02:09 02/09/05 (12)
  Just as a test, should the buzz be gone if the dimmers are turned off at the wall, or do they need to be shut off at the circuit panel in order to stop the noise?
  It would be easiest to replace the dimmers. Do you have any suggestions as to what kind?
  Thanks!
  Az
  - Re: Hum/Buzz - oldroadie 15:05:34 02/09/05 (11)
    Shut off at the panel is a definitive test. Some may still shunt AC when in the off postion.
    Try these guys for parts.
    http://www.mainstage.com/PDFs/mts_specialtylighting.pdf
    
    Tom
    - Re: Hum/Buzz - Az Barber 16:49:31 02/09/05 (10)
      Okay, I shut off the power for the dimmers, which also happened to be the same leg of power for the amps. I ran a 50ft heavy duty extension cord from a different circuit over to the amps, and hooked them up. Less buzz, but still some buzz. The only other thing I could find on this circuit was an incandescent bulb. There is a nearby referigerator, but I unplugged it just to make sure.
      The buzz is about 1/2 what it was, going from annoying to simply noticeable.
      The good news is that someone had evidently been working on this problem before me, as there is a dead GFCI outlet right near the amps. I followed the romex over to that same incandescent bulb that is the lone termination on the other leg (other than a couple of unused wall outlets on the other side of the room) so I will simply hook up the GFCI outlet and I'll have nearby power from another leg.
      But I would like to completely eliminate the buzz, do you have any other ideas?
      I can't begin to tell you how much I appreciate the help you've given so far!
      Az
      - Re: Hum/Buzz - oldroadie 04:37:55 02/10/05 (9)
        
        In Reply to: Re: Hum/Buzz posted by Az Barber on February 9, 2005 at 16:49:31:
        
        I'm concerned you do not have a ground.
        This could be extrememly dangerous if you're running a P.A. where you have guitar players singing, as the potential difference between the guitar, and the microphone could cause a shock or electrocution.
        You need to see if the building is grounded.
        Get yourself an inexpensive Radio Shack outlet checker to make sure all legs of AC have the same polarity references, and have a pro check out the breaker box to insure building grounding.
        You problem is compounded by dimmers, but the root of the problem seems to be unsafe AC. You can tear up gear, but more important, it can kill people.
        
        Tom
        
        Re: Hum/Buzz - Az Barber 04:48:26 02/10/05 (8)
        
        In Reply to: Re: Hum/Buzz posted by oldroadie on February 1, 2005 at 04:37:55:
        
        You may be right, I noticed that one of my powerstrips reports a wiring error on many of the outlets.
        I'll have that checked out ASAP!
        Thanks again!
        Az
        
        Re: Hum/Buzz - Az Barber 12:38:20 02/10/05 (7)
        
        In Reply to: Re: Hum/Buzz posted by Az Barber on February 1, 2005 at 04:48:26:
        
        Ok, here's an update: The outlets that were not grounded simply never had the ground wires hooked to them. The wires were run to the outlet boxes, simply twisted together and passed on. Easy enough to fix. The outlet that the equipment is plugged into was grounded fine and was on a different circuit. The ungrounded outlets are now grounded.
        The electrician unhooked the ground wire from the GFCI outlet and the buzz was about half what it was. He said that this was safe with a GFCI outlet as the GFCI would still trip and prevent any accidents. He could not come up with a reason for the rest of the buzz though... he was here for 2 1/2 hours. His solution was to add a completely seperate leg from the main panel and run it to a new subpanel specifically for the equipment as the noise seems to be coming down the neutral.
        This would be very expensive as it would require upgrading the main breaker panel and installing a new sub panel. The wire runs and new ground would actually be easy.
        So the result is about half the buzz, but no real reason or 100% solution.
        Thanks again for any ideas!
        Az
        
        Re: Hum/Buzz - oldroadie 19:12:57 02/10/05 (5)
        
        In Reply to: Re: Hum/Buzz posted by Az Barber on February 1, 2005 at 12:38:20:
        
        Bob Lee mentions a pin 1 problem, if you aren't familiar with what he is talking about, look here.
        http://www.rane.com/note110.html
        Also, the electrician looked at the ground distribution system in house, what about the earth ground?
        And then again, we are back at the SCR noise that the dimmers are throwing on the ground.
        If none of those fixes get 'er done, maybe it's time for a couple portable generators. Unless you're talking about a permanent install.
        
        Tom
        
        Re: Hum/Buzz - Az Barber 21:28:49 02/10/05 (4)
        
        In Reply to: Re: Hum/Buzz posted by oldroadie on February 1, 2005 at 19:12:57:
        
        Thanks for helping out guys! I really appreciate it!
        The pin 1 problem ain't it. First off, I'm using Jensen Isolators which have a switch to eliminate the Pin 1 problem, and I've tried consumer amps with unbalanced inputs... they all exhibit the same buzz.
        I did not know to check the earth ground. How is that checked? I know there's at least one metal rod jammed into the ground that has the tele, cable tv, and electrical service grounds attached to it. Is there a way to check it for resistance or potential?
        The dimmers were removed. The buzz is still there. If I get rid of the buzz, I'll retry the dimmers and see what happens. But right now, they are physically disconnected and the buzz still exists.
        I am considering solar and a bank of batteries!
        Az
        
        Re: Hum/Buzz - oldroadie 22:48:10 02/10/05 (3)
        
        In Reply to: Re: Hum/Buzz posted by Az Barber on February 1, 2005 at 21:28:49:
        
        Here's a link to a real good discussion of your issue.
        Pro Sound Web is a pretty good resource for any of this type of info.
        I'm afraid my basic skills have taken you about as far as I dare go.
        I don't like to play with AC too much, folks can get killed for bad advice.
        Good luck
        
        Tom
        http://srforums.prosoundweb.com/index.php/m/31420/2407/?SQ=5bb4d0e1f9346d189fc7acd8eac85a47#msg_31420 (Open in New Window)
        
        Re: Hum/Buzz - Jacques 14:03:23 02/12/05 (2)
        
        In Reply to: Re: Hum/Buzz posted by oldroadie on February 1, 2005 at 22:48:10:
        
        I got a neat idea on what in going on .
        As my answer is somehow long, and involves drawings, I posted it at:
        
        Good luck and patience in reading this page!
        http://www.atout-tech.com/autres/humnbuzz/Hum_and_Buzz_problem.html (Open in New Window)
        
        Re: Hum/Buzz - Az Barber 19:24:34 02/18/05 (0)
        
        In Reply to: Re: Hum/Buzz posted by Jacques on February 12, 2005 at 14:03:23:
        
        Thanks Jaques! Thanks to you, I found and repaired a neutral leak to ground. That reduced the hum to about half what it was. I then tied all my amps (balanced and unbalanced) together with a chassis ground hooked to my Jensen isolation transformer and...
        NO MORE BUZZ OR HUM! Even with my super sensitive speakers (105db at 1w/1m) you have to stick your ear into the horn to hear any noise at all.
        Even the dimmers have no effect at all!
        I'm so glad I don't have to listen to that annoying buzz anymore...
        Thanks again Jaques and Oldroadie!
        Az
        
        Re: Hum/Buzz - Az Barber 17:46:04 02/12/05 (0)
        
        In Reply to: Re: Hum/Buzz posted by Jacques on February 12, 2005 at 14:03:23:
        
        Wow, Thanks! I've read your message three times and even though I don't understand all of it, I can easily test for neutral leaks to ground. Since the previous owner did not properly hook the grounds up to several outlets, I suspect one or more outlets is incorrect causing the problem you describe.
        FWIW, I tried turning off every circuit except the one that powers the equipment off and I still got buzz.
        At any rate, you've given me several tests and a lot to think about! Thanks again!
        Az
        
        Re: Hum/Buzz - Bob Lee (QSC) 16:07:31 02/10/05 (0)
        
        In Reply to: Re: Hum/Buzz posted by Az Barber on February 1, 2005 at 12:38:20:
        
        A GFCI makes an ungrounded outlet only slightly safer, but still not safe.
        Do any of your pieces of equipment have a pin 1 problem?

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