Thorens TD160 hum

Discussion in 'Turntables' started by Jeffhill, May 18, 2017.

  1. Jeffhill

    Jeffhill New Member

    Messages:
    6
    Hi all. Looking for some guidance and experience here. I have a Thorens TD160 and was getting significant RF Ingres, a local AM radio station, coming through loud and clear on my phono channel.
    I just replaced the original interconnectors with Synapse High Performance Multi Media interconnectors by Belkin with a ground line.
    I was pleased that when I started up my turntable the radio station ingres had disappeared but I now have a hum on the left channel.
    When I disconnect the ground on the receiver the hum goes away but the AM radio station returns, although not as loud as prior to replacing the interconnectors.
    Any ideas, thoughts on what the issue may be?
     
  2. tnsilver

    tnsilver Super Member

    Messages:
    2,480
    Location:
    Boston
    The Thorens TD-160 default ground scheme is to ground the shield of the right channel (green). WHen you connect standard RCA phono cable without an external ground lead, you are already grounded by default. Then, when using an external ground wire (in addition) it creates a ground loop which manifests in humming. So the default grounding scheme must be altered before one can use an external ground wire. The radio broadcast through the phono stage is obviously an amp / preamp issue which you accidentally mitigate with the extra ground wire that serves as a grounded antenna. The am station audability is not a fault of the turntable.
     
  3. Jeffhill

    Jeffhill New Member

    Messages:
    6
    Thank you for the feedback.
    Could I ask how do you resolve the ground loop?
     
  4. bberkom

    bberkom AK Subscriber Subscriber

    Messages:
    995
    Location:
    Nashville, TN
    Either disconnect the internal ground for the cable shield or don't use the extra ground wire.
     
  5. tnsilver

    tnsilver Super Member

    Messages:
    2,480
    Location:
    Boston
    You don't have to but It's in the service manual.
    What you want to do if you insist on an external ground wire,
    is disconnect the the default ground wire from reaching the right
    channel shield. Basically just disconnect the tab that connects to
    the metal post (where the red X is)

    It looks like this in the hub:

    [​IMG]
     
  6. noisefreq

    noisefreq Active Member

    Messages:
    285
    Location:
    Independence
    After you get the grounding sorted out (I kept mine stock), you could try Ferrite Beads on all the AC cords of your turntable's signal path.
     
  7. Jeffhill

    Jeffhill New Member

    Messages:
    6
     
  8. Jeffhill

    Jeffhill New Member

    Messages:
    6
     
  9. noisefreq

    noisefreq Active Member

    Messages:
    285
    Location:
    Independence
    Mouser, Amazon...just goggle it, they're cheap.
     
  10. Jeffhill

    Jeffhill New Member

    Messages:
    6
    Thanks!
     

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