Ground phono amplifier without turntable?

Discussion in 'AV Receivers & Amplifiers' started by mtrack, Apr 13, 2016.

  1. mtrack

    mtrack
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    I have recently bought a Cambridge Audio AM10 amplifier and I can constantly hear a quiet humming noise. I assume this is because the phono input is not in use and/or is not grounded. Is there any way to ground the amplifier without the use of a turntable as I have no desire to use one?

    Thank you.
     
  2. Bbos37

    Bbos37
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    Have you tried other input?
     
  3. mtrack

    mtrack
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    I notice the hum on all the inputs, its just louder on the phono input. I don't actually have the phono input connected to anything, can I use the phono input for something other than a turntable?
     
  4. Bbos37

    Bbos37
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    The phono in put for turntable cannot be used for other sources.
    As for the hum try earthing the amp .
     
  5. mtrack

    mtrack
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    My amp uses a three pin power supply (UK style), does this not mean it is already earthed?
     
  6. camelot1971

    camelot1971
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    If there is a hum with nothing connected to the amp (other than the speakers) then you have a faulty amp. Is it a new or used one?
     
  7. mtrack

    mtrack
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    I will have to check later if there is a hum without anything connceted. Yes, it is a used amp so it could be faulty.

    Just to let you know, the hum is virtually inaudible when using speakers, yet when I use my headphones I can hear a constant him in the background.
     
  8. camelot1971

    camelot1971
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    Do you have another pair of headphones to try? Sometimes the connector makes poor contact in the socket and can cause a hum. It could be a poor quality headphone amp too.
     
  9. mtrack

    mtrack
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    Yes, I have tried a few different pairs of headphones but the issue still persists. Is there any reason why the hum is louder on the phono input?
     
  10. camelot1971

    camelot1971
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    A phono input has a pre amp built into it so will amplify any existing hum. You should only ever connect a turntable to that connection though.

    It does sound like there is a fault with the amp.
     
  11. mtrack

    mtrack
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    I did fear that I had received a faulty amp, hopefully I will be able to return it. Thank you very much for your help.
     
  12. mtrack

    mtrack
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    So I've just tried the amplifier again. The hum is still there without any inputs plugged in. Strangely, I have noticed that when I turn the treble up the hum gets louder, and when I turn it down it gets quieter.

    Anyone got any ideas?
     
    Last edited: Apr 14, 2016
  13. camelot1971

    camelot1971
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    It's broken? ;)
     
  14. mtrack

    mtrack
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    Yes, I think it might be haha. Time to return it then... Its always a risk buying used equipment, might splash out on something new.
     

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