Humming Sound as TT Arm Reaches the Centre

Discussion in 'Hi-Fi Stereo Systems & Separates' started by EddieTeflon, Dec 30, 2011.

  1. EddieTeflon

    EddieTeflon
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    Hello - I've recently attached my new Rega RP3 TT with TT-PSU power supply.

    There is an audible hum the nearer the arm is to the centre and even louder when taken past the centre. This hum stops when the platter is switched off. Is this right? Any idea how I stop/minimise this?

    Something else I note is that when moving the arm in and out of the rest (if that's what it's called) is a crackling sound a bit like static or interference. This happens with the motor on or off. This isn't a problem, but should it be doing this?

    The deck is placed on a hifi rack on a wooden floor and is very near the loudspeaker too. The loudspeaker will move soon (once I get permission!!) and the TT will have it's own wall mount.

    Thanks......
     
  2. nwgarratt

    nwgarratt
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    Have you got the deck grounded? There should be a thin wire from the deck to a grounding screw or attach it to something metal.
     
  3. Mr Pig

    Mr Pig
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    Sounds like the cartridge is picking up hum from the motor, is it a moving coil? The lower the output of the cart, the worse this will be.

    Either that or it's from a transformer in something sitting under the deck, the PSU?

    No, Rega arms earth through one of the returns from the cart so there's no separate earth lead. I usually works fine.
     
  4. BlueWizard

    BlueWizard
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    Also, are we talking 'Hum' or is it a droning 'rumble'?

    If a rumble, then it might be feedback from the speakers. That is the speakers are vibrating the tonearm, which is being transmitted to the speakers, which in turn is causing the tonearm to vibrate more - Feedback loop.

    If the speaker are close to the turntable, then this is a real possibility. I've noticed that my turntable gets more sensitive to 'rumble' as it moves to the center of the LP. Though I'm not sure why.

    Steve/bluewizard
     
  5. EddieTeflon

    EddieTeflon
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    Sorry for the delayed reply and thanks for your comments.....

    As Mr Pig says, there is no separate earth lead.

    My Apollo CD player is on the shelf under the deck with the amp on the next shelf and the PSU below that. And the cartridge is MM - Elys 2.

    It's more of a hum (to me at least) than a rumble. The speaker is only a few inches away from the deck. Christmas tree coming down today - so will have a move round and see if that helps.

    Also - found the hum the other day without the arm even moving. Held the arm and then touched my radiator and then the metal door handle - the hum stopped. Could this be down to the speaker too? Or could it be that the arm isn't properly earthed?

    Cheers again....
     
  6. Mr Pig

    Mr Pig
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    It sounds like an earth issue somewhere. They can be pest to pin down. Try all the simple stuff first like unplugging different boxes and moving cables around.
     
  7. BlueWizard

    BlueWizard
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    "Rumble" is a type of low frequency feedback. The speakers vibrated the tone arm, the tone arm sends the vibration to the amp, which causes the speakers to vibrate that that frequency, which then in turn causes the tone arm to vibrate even more.

    Have you tried to simply move the tone arm near the center with no record playing? If it occurs simply from movement, then it is some type of electrical noise that is being picked up.

    The motor is only 24v and the system is earth grounded through the shields of the audio wires, as near as I can tell. But internally, the tone arm is connected to these Shields. If that connection is broken, it could cause noise. All my best guess from reading the extremely lean and uninformative owner's manual on-line.

    I would look at the placement of the Audio interconnect cables of the Turntable. Do they cross any power wires? If you move them does the sound stay the same, get better, get worse?

    Steve/bluewizard.
     
  8. EddieTeflon

    EddieTeflon
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    Yes - tried it without playing a record. It's louder when the the arm passes the spindle. Making me think its cables etc behind as the cartridge is closer to the rear of the deck. Will be having a shift round soon and getting the Rega wall mounted TT shelf when in stock. Will report back with results.

    Thanks all for your comments...
     
  9. EddieTeflon

    EddieTeflon
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    Moved the audio cables so they don't touch any power cables - the hum is still there but the crackle when touching the arm or cartridge head has stopped. Didn't realise what a difference cable placement makes.
     
  10. EddieTeflon

    EddieTeflon
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    Sorry been away for a couple of months, hence no update.

    The crackling returned. The dealer agreed there was a problem too and I had a new deck within a few days. Now wall mounted and sounding great!

    Just need to look for some new speakers now........!
     

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