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Aaagh! sub hum.

Discussion in 'Subwoofers' started by richard plumb, Dec 30, 2002.

  1. richard plumb

    richard plumb
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    Occasionally read things about this, but never had the problem so didn't pay attention. Set up my system last week and all was well until I connected the DVD player and projector - sub hum.

    Now this is on the mission FS1-AV sub, and it even does it when the receiver and DVD player is switched off.

    Can anyone provide some initial guidance of where I should be looking to avoid this? It isn't loud, and I'm currently switching the speakers off after viewing. but that isn't very convenient and I'd like to try and get rid of it.
     
  2. magking

    magking
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    Do a serch for earth loop.
    Try disconnecting everything from your sub except the mains. If it stops humming, connect the low level again, if it starts to hum again you have a earth loop.
     
  3. juboy

    juboy
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    Also try and keep the sub's power cable and the cable from the amp to the sub as far apart as is practical, ideally a minimum of 5 to 6 inches apart. If the cables need to cross, try and ensure they cross at right angles and avoid running them parallel.
     
  4. BK Electronics

    BK Electronics
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    You also get a problem if all the equipment is double insulated, everyting is up in the air without any reference.

    As previously mentioned do a search on hum, there should be lots of info.
     
  5. richard plumb

    richard plumb
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    thanks, I'll try a search.

    The low level isn't connected to the sub - its a sub-sat system and I'm only running the main speakers into it, I have a separate sub for low level.

    The speaker cables are also routed completely away from all mains cables.

    Could be the insulated thing - it started to happen when I connected my DVD and projector up, and the PJ has long video cable runs across the ceiling (but again the power lead is in a different direction)
     
  6. MartinCo

    MartinCo
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    richard, does the fs1 sub go into a power saving mode like the fs2 one? (amber light instead of green).

    a few of us have had this happen for different reasons, some just a minor wiring problem and very easy to find/ fix.

    one person however did mention a problem with the mains in their house causing this - do a search for more info.
     
  7. richard plumb

    richard plumb
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    previously, when there was no signal from the amp, the FS1 would switch to standby after a while, and the LED would go red. Now it stays green.
     
  8. MartinCo

    MartinCo
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    there is your problem then... had similar myself an odd time with the fs2s after moving them around.

    recheck all cables then (to satellites and from the sub to amp), even a loose connection might cause this.

    at least worth checking.
     
  9. Geoffc10

    Geoffc10
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    i had hum from my speakers when i attached my new projector to my system, it turned out that the sub was faulty, cost £80 to fix, but had a 3 year warranty, might be worth sending yours off to be checked.
     
  10. richard plumb

    richard plumb
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    just noticed that the hum went away when I disconnected the ProV, so presumably its part of the projector cabling that is picking up something.

    I might try rewiring the swictching part of it to go through the amp, which will hopefully provide more isolation when it is switched off.
     
  11. magking

    magking
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    Sounds like a earth loop through the PJ.
    I also have it. When i use the VCR in on amp, which is connected to the PJ with composite, my Rel Q400 hums, but only when i select that input on the amp. When i watch DVD's i don't hum because that is connected direct to PJ (not through amp).

    Have'nt tested if Godzilla hums in the same way, will check tonight.
     
  12. James45

    James45
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    Do you have a bath before you watch DVDs then?:D :D
     
  13. buba

    buba
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    Richard.

    I had a similar problem.
    To check if it is a ground loop try this…
    Find earth on the back of your amp and attach a piece of speaker cable, with the other end connect to your Sub on a suitable earth point.
    Power up and hopefully cured your Hum…

    :D
     
  14. magking

    magking
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    Ooops!
    Thats what happens when i post from work, my boss is looking over my sholder all the time.:(
     

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