sub making speakers buzz

Discussion in 'Home Cinema Speakers' started by Sleepy, Jun 4, 2008.

  1. Sleepy

    Sleepy
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    hi, i have noticed when my sub is plugged in all my speakers buzz through the tweeter with a hum from the sub. Unplug the sub and the buzzing goes.

    It can only be noticed if you are right next to the speakers but the buzzing is there.

    Seems strange as its only there if the sub is connected, like its interfering.

    Is this normal and does anybody else have this?

    The sub and speakers are quad l-ites
     
  2. -Hitman-

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    Sounds like a ground loop to me, some Ppl remove the earth from the plug supplying power to the sub, can also be done using and earth isolator plug which basically does the same thing.
     
  3. Sleepy

    Sleepy
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    thanks i will give this a try
     
  4. namuk

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    me mate had this for ages found out one day it was the sub lead very odd
     
  5. Member 281695

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    Most likely a ground loop as Hitman said. Very common, and usually solved by disconnecting one of the grounds, thus interrupting the closed loop.

    If ground currents flows through a closed loop they end up in the signal path and becomes audible. Some subs have separate supply ground/signal ground eliminating this problem.

    :)
     
  6. BlueWizard

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    Another potential solution might be to plug them both into the same source; literally into the same outlet.

    Most likely the plugs are polarized, so that solves one problem, but if the plug can go in either way, try reversing it. Perhaps UK plugs can't be reverse as it possible in the USA.

    It could also be poor or corroded connection of the wall wires to the wall plug. If voltage is being lost in the wire connection, that creates a voltage difference between the two plugs. You can look and check this out, but if you are not adept at electrical work, I wouldn't mess with cleaning the connections.
     
  7. Mark.Yudkin

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    I would very strongly recommend not following Hitman's extremely fooolhardy advice. The earth is there for very good safety reasons and removing it is a bad idea.

    Fortunately, earth loops involving subs are readily rectified without playing Russian roulette. The first thing to do is track it down. Ground loops involve two paths: so far you have only identified one of them.

    1) The most common cause is an aerial lead. Unplug all sources of radio and TV (satellite, freeview, cable, antenna). Does the hum go away? If so, you need a coax ground loop isolator. (This link is rather expensive, your dealer should manage something for under half the price). Insert one per TV / radio coax lead.

    2) As BlueWizard says, plug both the amp and the sub into the same wall socket (UK plugs cannot be reversed), using a power strip.

    3) If neither of the above work, you need an RCA ground loop isolator. Insert it between the amp and the subwoofer.
     
  8. Jamie

    Jamie
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    Alternatively if you can't notice it in normal use forget about it unless you can solve by moving the plugs about.

    Another thing to check (may just be my amp though)
    My Arcam AVR200 has a ground/ground lift switch. I had a very slight hum (again only noticeable with my ears tright next to the speakers so didn't worry me) moving the switch to ground lift made it go away. I'm guessing this removes the source of the ground loop.
     
  9. AgentCool

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    For some reason, my speakers have started to do the same thing as the OP's. I've had my receiver (Denon 2805) and subwoofer (Wharfedale Diamond SW150) for over 3 years and yet, completely out-of-the-blue, all of the speakers now make a low-pitched humming sound whenever the receiver is switched on. It goes away when I unplug the sub's RCA connection (connected to the receiver with a QED Qontour cable) but it strikes me as odd that this has started happening after all this time. The only thing I have changed in my system recently is my HD DVD player but the new one is connected in exactly the same way as the old one and the hum persists when this is disconnected anyway.

    Out of interest, another way of getting rid of the hum is by plugging 2 RCA cables into the front of the receiver and connecting the other end - a 3.5mm socket - into my laptop.

    Would an RCA ground loop isolator between the sub and receiver solve the problem?
     
  10. Member 281695

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    Ground loops can be tricky sometimes, but once you have pinpointed the problem having disconnected everything except the units that cause hum it´s almost always quite easily fixed. A ground isolator may very well do the trick. But are you sure nothing is changed in any way? Like a cable tv box being connected to the receiver or similar?

    TV boxes are commonly known to cause ground loops.

    :)
     
  11. AgentCool

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    Nope, no change in TV/Satellite box or anything though I did disconnect the satellite feed from my Sky+ box to check. This did eliminate some of the hum but it was still there. The only change I've made is I swapped my Toshiba HD-EP35 for a Toshiba HD-XE1 but that's only connected to the receiver using a Toslink cable.

    I thought that I may have done something when pulling about with the wires at the back but I've checked everything and it's all as it was.
     
  12. Member 281695

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    Did the noise develop gradually or suddenly? What is the least no of units you can connect together and still get the noise?
     
  13. Mark.Yudkin

    Mark.Yudkin
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    If its not a coax feed (unplug every coax you have - radio, TV, satellite, cable), then the RCA ground loop isolator I gave above should fix the problem.
     
  14. AgentCool

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    Solved it! :clap: There I was messing around with connections to the receiver and it turns out it was a much more bizarre, unexpected problem. I have a Thor 2-into-1 HDMI non-powered multi-plug which I use to connect my Toshiba HD DVD player and PS3 into my TV as it only has 1 HDMI input. When I was installing my Tosh XE1 I must have accidentally disconnected the PS3 HDMI lead from the Thor multi-plug. Plugging it back in immediately solved the problem. Neither the Sky box nor the HD DVD player are connected to the receiver electrically (both optically) so presumably the problem must have been through some complex passing of current through a whole host of wires and devices before it got to the receiver.
     
    Last edited: Jul 2, 2008
  15. Mark.Yudkin

    Mark.Yudkin
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    Chances are your TV is connected to the amp, so that both your Sky and your HD DVD are electrically connected, albeit indirectly.

    What you've probably done is to reintroduce a ground path to a common ground, thus moving the sub out of that path. In any case, it's fixed.
     

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