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Grounding tags on phono stages.

Discussion in 'audio' started by ciderglider, Oct 4, 2011.

  1. ciderglider

    ciderglider pfm Member

    Would someone be kind enough to explain the rationale for grounding tags on phono stages? Why take an extra ground lead from the turntable?
     
  2. dweezil

    dweezil pfm Member

    Used to be important to control mains interference so you would have grounding points on amp and TT as well.

    I haven't used an earth lead for years, i think the TT motor is isolated by the power supply as is the phono amp.

    My current pre weighs about 5 times as much as the last integrated i had with earth tab so i reckon that has a better power supply too.

    general routine was to connect / disconnect if you had a bit of hum.
     
  3. sq225917

    sq225917 situation engineer

    It allows you to run an earth/shield from the tonearm that isn't input directly into the differential stage that drives the amp, so it 'can' reduce noise.
     
  4. DougBradyHiFi

    DougBradyHiFi pfm Member

    The grounding lead/tag is usually connected to the tone-arm tube/metalwork within the arm structure. It earths the pipe of the arm and shields the 4 wires that carry the low signal from the cartridge. The cables that exit from the base of the arm to the phono plugs are normally shielded anyway, but without the separate lead the internal wires pick up interference, especially if you touch the arm/headshell-you then act as an aerial and make the hum even louder. In some circumstances, usually with moving coil cartridges, leaving off the separate tag/lead makes no difference because of the very low coil resistance of the cartridge(a few ohms). This almost short circuits the phono stage input and 'dumps' the interference directly to signal ground, this is normally connected internally to the chassis/earth terminal within the circuitry.
     
  5. uncl_nigel

    uncl_nigel pfm Member

    Thanks. I have low output MCs on both decks...
     
  6. ciderglider

    ciderglider pfm Member

    Thanks to all for the learned replies.
     

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