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    Phono Grounding

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    aguaazul

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    Location : Livermore, CA

    Phono Grounding

    Post by aguaazul on Wed Apr 25, 2018 8:22 pm

    Both the tube phono preamp and tube preamp DS2 / SP-14 have ground lugs in the back.
    Phono has a power ground connection
    Phono Pre is does not have a ground power wire.
    Preamp does have a power ground line.

    I will connect the phono ground to the phono pre ground lug.
    My question is do I need to connect a ground wire from the phono pre to the main preamp.

    Blue
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    sKiZo

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    Location : Michigan USA

    Re: Phono Grounding

    Post by sKiZo on Wed Apr 25, 2018 9:21 pm

    Not a bad idea - I'd also add a wire to house common so all the junk the other wires picks up has a place to exit the system. The plate mounting screw of any modern outlet has a path to the receptacle's ground wire, so just piggyback the wire to that using a ring connector.
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    aguaazul

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    Re: Phono Grounding

    Post by aguaazul on Thu Apr 26, 2018 12:57 am

    Thanks Skizzo.
    Except I was wrong with the phono power cable.
    Phono is a 2 prong, hot & common plug. No ground.

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    peterh

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    Re: Phono Grounding

    Post by peterh on Thu Apr 26, 2018 2:17 am

    aguaazul wrote:Both the tube phono preamp and tube preamp DS2 / SP-14 have ground lugs in the back.
    Phono has a power ground connection
    Phono Pre is does not have a ground power wire.
    Preamp does have a power ground line.

    I will connect the phono ground to the phono pre ground lug.
    My question is do I need to connect a ground wire from the phono pre to the main preamp.

    Blue
    There is no definite answer here, but with amps on you can connect in various
    combination while listening to the hum.
    As it is a very low level signal here the slightest change will make audio difference.

    You also should have a ground connection to the tonearm / plint to test with.

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    Peter W.

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    Location : Melrose Park, PA

    Re: Phono Grounding

    Post by Peter W. on Thu Apr 26, 2018 6:08 am

    aguaazul wrote:Both the tube phono preamp and tube preamp DS2 / SP-14 have ground lugs in the back.
    Phono has a power ground connection
    Phono Pre is does not have a ground power wire.
    Preamp does have a power ground line.

    I will connect the phono ground to the phono pre ground lug.
    My question is do I need to connect a ground wire from the phono pre to the main preamp.

    Blue

    Several US makers, amongst which were AR, Rabco (Latter-day HK units) and one more that I do not remember stated in their literature that the TT Ground wire should be connected to one of the headshells. AR TTs came from the factory with the ground connected to the left headshell.

    a) Think it through: The preamp/amp/receiver ground lugs are connected to the chassis sheet metal.
    b) In many (but not all) cases, the phono input grounds are isolated from the chassis sheet metal (Dynaco/AR/HK/Revox/Hafler).
    c) Meaning that the chassis ground (external lug) could easily be at a different potential than the phono preamp ground. Even if only by a few ohms.
    d) Not a good result.

    Solder the ground wire to a headshell and be done with it. For the last 42 years, mine have been that way and never a bit of hum.

    As to adding an external ground to the rest of your equipment - get out your trusty VOM and measure in AC and DC volts from each chassis to a known-good ground, and to each other. If you get more than a vanishingly few MV, find out what is going on, and fix it!! THEN - add the external ground.
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    aguaazul

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    Re: Phono Grounding

    Post by aguaazul on Thu Apr 26, 2018 1:34 pm

    After a little testing, there is no hum with just the phono connected to the phono pre.
    When I add a ground from the phono pre to the SP-14, plenty of hum.
    Remove it and quiet again. Not as quiet as the DAC, but zero hum.
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    Peter W.

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    Location : Melrose Park, PA

    Re: Phono Grounding

    Post by Peter W. on Thu Apr 26, 2018 1:43 pm

    aguaazul wrote:After a little testing, there is no hum with just the phono connected to the phono pre.
    When I add a ground from the phono pre to the SP-14, plenty of hum.
    Remove it and quiet again. Not as quiet as the DAC, but zero hum.

    Yep. No surprise there.

    Did you try to a headshell?
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    aguaazul

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    Re: Phono Grounding

    Post by aguaazul on Thu Apr 26, 2018 1:52 pm

    Did not need go that far. I'd like to see photo's of that procedure.
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    Peter W.

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    Location : Melrose Park, PA

    Re: Phono Grounding

    Post by Peter W. on Thu Apr 26, 2018 2:17 pm

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    Pillo69

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    Re: Phono Grounding

    Post by Pillo69 on Thu Apr 26, 2018 2:19 pm

    The ground wire of the arm / turntable must be connected to the chassis / connector of the first equipment (preamp phono), the rest of the equipment has the ground interconnected.
    Making more connections can cause a loop that causes buzzing.
    Note that with some capsules it may be necessary to remove the ground wire.
    If the turntable does not have a ground wire, it may be included in the negative of the left channel (as you have already commented).

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