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isolating electrical noise in monitors

Discussion in 'Monitoring / Headphones' started by sshack, Apr 11, 2008.

  1. sshack

    sshack Active Member

    So I've recently noticed that when my monitors are on (with nothing playing/coming out of them) that I have some really bad white noise going on. I'm not certain why I haven't heard it before, but the only thing that I can think of is that my room has recently been treated with various Auralex items as well as some thick curtains, etc. It's basically a lot more quiet and revealing.

    I'm not certain if this is an electrical issue or not, but let me spout out some info to help you help me.

    *Monitors are HS-80Ms, purchased new just a few months ago.

    *Speaker cables are nothing fancy, standard stuff that I use between my amp heads and their cabs.

    *Just about every guitar I have (single coil and/or HB) is very sensitive to the computer and the lamps that I have in the room. I usually have to position myself in the 'just right' position and turn off all lamps when tracking to avoid noise/hum. I do NOT have an overhead light.

    *All recording equipment is running through a UPS, amps are through surge protectors on different outlets.

    *Whenever I plug in my printer and my monitors are on at the same time, a nasty, screeching noise comes out of the speakers...this get worse when I actually turn the printer on. Needless to say, I print with the speakers OFF and unplug the printer when they're ON.

    *My house was built in '68 and of the few plugs or outlets that I've changed or installed throughout the house, I'm fairly certain that all of the wiring is original. Big, thick BLACK and WHITE wires.


    I've tried different outlets in my room, surge protectors, ground lifts, etc...and nothing helps. The only other thing that I can think to do of my own accord would be to buy some nice/higher end speaker cables. I have however called an electrician just to talk to them and maybe have them come out to diagnose, etc.


    Anyone have thoughts or ideas that they care to share?

    Thank you.
     
  2. Cucco

    Cucco Distinguished Member

    Just a couple words -

    1 - since these are powered speakers, you have to be careful of the lines you're feeding them. If there's noise in the line (unbalanced??), then you're going to amplify that - a LOT.

    2 - Most speakers with built-in amps put out their own noise. This is a function of the mass amounts of energy present at the amp in its state of rest. Not all of that energy can be dissipated via heat.

    Cheers-
    J
     
  3. sshack

    sshack Active Member

    Point(s) taken Jeremy, thank you.

    I'm no pro, and haven't been around tons of recording equipment, but this is enough noise where I don't think your second point is the case.

    I have no problem with buying some better cables. I'd love some suggestions? I'm looking at only needing 4 - 6 feet.

    /Shack
     
  4. Cucco

    Cucco Distinguished Member

    Fair enough - not sure what you meant by "some really bad white noise going on..."

    Are the cables you are using to connect unbalanced or balanced? If they're balanced, I doubt this is your problem. If they're unbalanced, I still have my doubts, but it's possible.
     
  5. sshack

    sshack Active Member

    How do you tell the difference, sorry, I don't know.

    It's almost like a faint ground hum with some high end hiss. I could record it for you.
    :lol:
     
  6. Cucco

    Cucco Distinguished Member

    Nah...don't worry about that. I wouldn't be able to listen to it until Monday. That won't help you.

    What kind of connections are you using:
    TRS
    TS
    XLR
    RCA (phono)

    to go from the output of your audio interface (soundcard, mixer, etc.) into your monitors? What are the monitors plugging into? The answers to these questions will likely tell me whether you're using balanced or unbalanced.

    Cheers-
    J.

    PS - based on the use of the word HUM, I'm now thinking it might in fact be a cable-borne issue.
     
  7. sshack

    sshack Active Member

    1/4" TS from the monitors to the Duet.
     
  8. Cucco

    Cucco Distinguished Member

    Can you switch to TRS?

    I'm assuming the Duet offers balanced output??
     
  9. sshack

    sshack Active Member

    Doesn't look like it. According to the manual it offers two unbalanced -10dBV line outputs for powered speakers.
     
  10. Link555

    Link555 Well-Known Member

    Wait a sec, your speaker cables are they sheilded? or are they the standard speaker cable meant to go from a power amp to a speaker?

    I agree TRS or XLR would be the way to go.
     
  11. sshack

    sshack Active Member

    Standard cables that I've used from my amp heads to the cabs. I'm fairly certain that they are shielded.
    FWIW, they're noiseless when I use them in that capacity, though I recognize this isn't exactly the same, that's why I'm asking.
     
  12. Cucco

    Cucco Distinguished Member

    Well, that friggin blows...unbalanced out only?

    Normally, I have no beef with unbal (in fact, in some apps, I prefer it). But given the fact that this product is designed specifically for people who will likely be using it in less-than-ideal power and RF/EM conditions, I would have expected nothing less than balanced.

    Anyway - Link's question is spot on - is it shielded cable or are you using true "speaker" cable?
     
  13. sshack

    sshack Active Member

    I just tested with a Monster cable that I know is shielded and that I currently use with my guitar rigs. The problem still exists.

    Since the outputs on the Duet are 1/4" only, I can't try an XLR.
     
  14. Cucco

    Cucco Distinguished Member

    Bear in mind, they're noiseless there because they are *after* the amplification stage. In other words, the noise that they may or may not pick up is not amplified, it's just mixed at a very low level with your amplified levels.

    I would take the laptop (presumbly...or desktop if I'm wrong), the duet and the monitors into a different room. Put them as close to eachother as possible and then fire them up. If you're still getting hum...tough to say.

    If you're not or it's changed or decreased, I would say the fault lies with the unbalanced line out.

    Cheers-
    J.
     
  15. Cucco

    Cucco Distinguished Member

    It wouldn't help even if you did. Just because it's XLR doesn't make it balanced. The differential signal makes it balanced. If that ain't there, it ain't there.
     
  16. sshack

    sshack Active Member

    Not to say it isn't possible, but that'd be a MAJOR PITA. I'm running an iMac that has more connections tucked behind my desk than I have time to deal with.

    I'm not lazy, I'm just not to that point yet. Given the other electrical gremlins that are in this house, it won't bother me at all to have an electrician come out just to assess what I have going on. I honestly figured that the UPS would help clear it up, but to no avail. Too bad it doesn't appear to be something as simple as a cable.

    Just for future reference, when I jump to my next interface (8 channel), should I look for something that has balanced outputs, or will it just be a standard feature at that point?
     
  17. Cucco

    Cucco Distinguished Member

    Did you try cutting the breaker after you put everything on the UPS?
     
  18. sshack

    sshack Active Member

    I did not. That sounds like a simple enough idea. How would that work?
     
  19. Cucco

    Cucco Distinguished Member

    Well - think of it this way -
    If you're getting interference (air-borne) from electrical lines or other devices, simply running it through a UPS won't do much. (Also, many UPS systems don't actually do anything to the power until there's a blackout. Even brown-outs don't trigger some UPSs).

    By cutting the mains, you'll isolate your entire system and elimate any possibility of dirty power as well as air borne interference.
     
  20. Cucco

    Cucco Distinguished Member

    Just make sure the UPS is adequately charged and capable of maintaining your power for a minute or so (could be a challenge with powered monitors).
     

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