Monitor noise problem

Discussion in 'Recording/Live Sound' started by scottlr, Jul 16, 2006.

  1. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    This doesn't affect my recording, it is just an annoyance. I have a pair of KRK Rokit RP8s connected to a Tascam US-122 that is connected to my G4. I just leave them connected as my computer speakers when I am not recording, so that when I click on music links, etc., I get nice sound quality.

    The problem is that they are constantly making high frequency noise that seems to correlate to the G4. If I scroll, the noise stops while I scroll, then comes back when I stop. Any HD activity comes through them as well. This is not loud, but when there is no other sounds in the room, it is very noticeable. And every now and then, I get a lower range pulse or pop sound, that is again, not loud, but very noticeable.

    The Tascam is set up next to the tower, and one of the monitors is on a shelf about 6-8 above the tower. Before I got these monitors, I was just using a pair of JBL2600 bookshelf speakers, and I never recall hearing this noise on them. Any ideas?
     
  2. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    No ideas... anyone?
     
  3. dash_doc

    dash_doc Member

    Messages:
    554
    Joined:
    Jun 26, 2002
    Location:
    San Pedro CA
    I don't really know the spacific equipment you are using here, but your discription makes it sound like EMI/RFI interference from the computer. The KRK's are powered correct? I would try moving the Tascam and or the cables running from it to the KRK's, also if possible run a balenced cable to the KRK's from the Tascam.
     
  4. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    As far as I can tell, the Tascam has no Balanced input/output. I do need to redo my studio set up as it has just been thrown together as I get new stuff. Yes, the KRKs are powered, the JBLs were not. I have been thinking of tearing the whole thing down and redoing it all anyway, so maybe that is another good reason to do so. Thanks for replying!
     
  5. LSchefman

    LSchefman Member

    Messages:
    13,449
    Joined:
    Jan 4, 2002
    Sometimes ground loops will enable RFI/EMI noise, and sometimes what seems like RFI will be loop noise.

    There are lots of fixes for this problem. I'll bet that's what it is.
     
  6. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    Thanks, man! As soon as I get the time to start this redo project, I'll be looking at all of that stuff. I know if I start, I'll want to finish the same day, and it'll take all day to do it.
     
  7. krash

    krash Member

    Messages:
    64
    Joined:
    Mar 7, 2006
    you might try some ferrite beads on the ends of the cables, near as possible to the connectors.

    my suspicion is it's not in fact radiated emissions (RFI) but conducted ... through the power wiring. does it go away when the computer monitor is unplugged or powered off? this could give you a clue.

    Anyway, a handful of snap-on ferrite beads could help if it's RF type noise. A better designed power supply or enclosure in the offending product would help more.
     
  8. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    Hmmm, what's a ferrite bead, and where do you get them? I just powered off the computer monitor and it made no difference. The noise seems to be altered by computer functions, like mousing, and when a drive is writing/accessing.
     
  9. TAVD

    TAVD Guitar Player Gold Supporting Member

    Messages:
    3,475
    Joined:
    Jan 20, 2004
    Location:
    MD
    Just turning off the computer might not tell you much. Try some 2 prong AC adapters on the monitors to lift the ground. With unbalanced cables and a usb interface, both prone to ground loops, I think Les is on to something. The ferrite beads won't do anything at all for ground loops.

    It does seem odd that the interference stops when you move the mouse, etc. Try moving the monitors further away from the computer monitor, if they're less than 1' away.
     
  10. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    I think I need to redesign the studio setup, as NOTHING is very well placed. The problem is what I *want* to do, will not set well with my wife. The studio is a large nook off the main basement family room. So, she gets all nervous if I want to something that is correct for recording, but not correct for her decorating ideas LOL
     
  11. DWB1960

    DWB1960 Senior Member

    Messages:
    22,006
    Joined:
    Dec 13, 2005
    Location:
    SoCal by way of Boston
    Scott. shoot me an email donb@kscind.com. I can get you some ferrite beads and explain how to use them.
     
  12. LSchefman

    LSchefman Member

    Messages:
    13,449
    Joined:
    Jan 4, 2002
    Not that I want to inject too much into this discussion, but...ferrite beads will do nothing if it's a ground loop problem. Denyle's suggestion re: adapters is a good method to determine if you have a ground loop, and there are others. A good source of information on ground loops, their causes, and possible solutions, is the Rane website.

    It's also possible that instead of lifting the ground, a piece of gear needs an additional ground connection to its chassis. I use a grounding block in my studio, star-grounded to a true earth ground, to solve those kinds of problems (which, thankfully, are few and far between).
     
  13. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    Well, upon a little investigation, it may be the cable connecting the left side that is causing much of this. When I unplug it, there is little noise at all coming from the right monitor. I am going to first get a new cable and see if that makes any difference.

    OH, and it's not just moving the mouse that stops it, it is using the mouse. Click hold and drag on something, like a scroll bar, for instance, that makes the noise go away while the object is being dragged.
     
  14. LSchefman

    LSchefman Member

    Messages:
    13,449
    Joined:
    Jan 4, 2002
    I'd be surprised if it's the cable, because you didn't say you're getting intermittent audio. If the noise is related somehow to the mouse, that's interesting. Is it a wireless mouse? You might try experimenting with a different mouse.

    You may have two ground loops, each reinforcing the other. As an experiment, have you tried lifting the AC ground to the amp or monitors with a 3>2 adapter?
     
  15. TAVD

    TAVD Guitar Player Gold Supporting Member

    Messages:
    3,475
    Joined:
    Jan 20, 2004
    Location:
    MD
    Did any G4's have any power supply issues? I seem to recall hearing about some questionable power supplies but I don't know if it was the G4 or something else.
     
  16. GuitslingerTim

    GuitslingerTim Member

    Messages:
    2,178
    Joined:
    Jan 9, 2005
    +1. Provided the board or breakout box is properly grounded, lifting the monitor power supply ground with an adapter is the first logical step toward a solution.
     
  17. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    OK, I'll try that, too. But wriggling the cable to the left speaker, has noticeably lowered the volume of the noise. So, I am still going to replace that cable.

    Not sure about the G4 power supply thing. Mine has been pretty reliable so far.

    Donnie B has graciously provided me some ferrite beads, so, I'll be doing that as well. Thanks, Don!
     
  18. scottlr

    scottlr Member

    Messages:
    22,887
    Joined:
    May 14, 2006
    Location:
    Born & raised in Texas; stranded in Iowa
    OK, I have not yet tried the ground lifting thing, but I replaced the bad cable, and put the ferrite beads on both cables. The noise is now 75-85% better. I can still hear it, but it is really a faint high frequency whine.
    When I get around to reorganizing things here, I'll also try lifting the ground. After all of the noise it was making, it's damn tolerable now.
    Thanks to all, especially Don!
     

Share This Page