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Re: V9 output to audio card?

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  • Ken
    OK, it s getting better now - OR maybe I m just more confused. By mains frequecy you mean the 60 (or 50) cycles of the power line? A lowish value (such as
    Message 1 of 10 , Jan 1, 2009
      OK, it's getting better now - OR maybe I'm just more confused.

      By "mains frequecy" you mean the 60 (or 50) cycles of the power line?
      A "lowish" value (such as in the pF range?) will loook like a brick
      wall to the low freq while allowing the "spiky" USB signal to pass....
      Is there any signals as such on the ground wire of the USB connection?
      AND does the ground wire not need to be a DC ground that would be
      blocked by a capacitor? I guess I am still confused.... I'm starting
      the new year in my "normal" state of mind- CONFUSED.

      OR are you suggesting putting this "lowish" value capacitor on all the
      USB wires to isolate them to prevent any ground loops?

      Thanks to all for info shared in these forums.

      73 de Ken H> K9FV


      > Well, the current through ground loops is basically at mains
      frequency and
      > its lower harmonics. A lowish value capacitor will have a highish
      impedance
      > at these frequencies so little current will flow.
      > The capacitor offers a relatively low impedance at the higher
      frequencies so
      > passing the spiky USB signal. In my case the impedance of the ground
      > connection must have been high enough to suppress this signal.
      >
      > 73 Alan G4ZFQ
      >
    • Alan
      ... From: Ken ... Yes, I thought I was talking the wrong language! Over here we often call the 50Hz main power supply line the mains ... That depends on
      Message 2 of 10 , Jan 2, 2009
        ----- Original Message -----
        From: "Ken" >
        > By "mains frequecy" you mean the 60 (or 50) cycles of the power line?

        Yes, I thought I was talking the wrong language! Over here we often call the
        50Hz main power supply line "the mains"

        > A "lowish" value (such as in the pF range?)

        That depends on the frequency and the line impedance. 10nF is a small value
        at 50/60Hz so offers a considerably higher impedance than the direct
        connection via the audio cable. Therefore little LF current flows through
        the capacitor.

        > while allowing the "spiky" USB signal to pass....
        > Is there any signals as such on the ground wire of the USB connection?

        The spiky USB signal has to return to ground, so yes, they are there. If it
        is a good low-resistance ground connection they will not be noticed.

        > AND does the ground wire not need to be a DC ground that would be
        > blocked by a capacitor?

        The DC ground is connected via the audio ground.

        > are you suggesting putting this "lowish" value capacitor on all the
        > USB wires to isolate them to prevent any ground loops?

        If there is a good ground return to the USB by way of the audio cable then
        this capacitor may not be needed. I leave the USB ground disconnected to
        avoid a ground loop at low frequencies. The 10nF capacitor just gives the
        spiky signal an alternative route.

        Again I stress that this is just the way I have done it. It seems that to
        get the best results it may be necessary for people to experiment until they
        are satisfied, their conclusions may differ from mine .

        73 Alan G4ZFQ
      • Ken
        ... connection? ... there. If it ... OK Alan, NOW it s getting clear to me - the signals will still have the ground return via the low value capacitor while
        Message 3 of 10 , Jan 2, 2009
          > > while allowing the "spiky" USB signal to pass....
          > > Is there any signals as such on the ground wire of the USB
          connection?
          >
          > The spiky USB signal has to return to ground, so yes, they are
          there. If it
          > is a good low-resistance ground connection they will not be noticed.

          OK Alan, NOW it's getting clear to me - the signals will still have
          the ground return via the low value capacitor while the DC ground
          would be blocked by the low value resistor. The DC ground is
          provided by the speaker ground.

          > > AND does the ground wire not need to be a DC ground that would be
          > > blocked by a capacitor?
          >
          > The DC ground is connected via the audio ground.

          Thank you again Alan for being patience - I really think I do
          understand better now.

          73 de Ken H> K9FV
        • R. R. Robson
          ... call the ... small value ... through ... there. If it ... cable then ... disconnected to ... gives the ... that to ... until they ... Ah, the brits and the
          Message 4 of 10 , Jan 2, 2009
            --- In softrock40@yahoogroups.com, "Alan" <g4zfq@...> wrote:
            >
            >
            > ----- Original Message -----
            > From: "Ken" >
            > > By "mains frequecy" you mean the 60 (or 50) cycles of the power line?
            >
            > Yes, I thought I was talking the wrong language! Over here we often
            call the
            > 50Hz main power supply line "the mains"
            >
            > > A "lowish" value (such as in the pF range?)
            >
            > That depends on the frequency and the line impedance. 10nF is a
            small value
            > at 50/60Hz so offers a considerably higher impedance than the direct
            > connection via the audio cable. Therefore little LF current flows
            through
            > the capacitor.
            >
            > > while allowing the "spiky" USB signal to pass....
            > > Is there any signals as such on the ground wire of the USB connection?
            >
            > The spiky USB signal has to return to ground, so yes, they are
            there. If it
            > is a good low-resistance ground connection they will not be noticed.
            >
            > > AND does the ground wire not need to be a DC ground that would be
            > > blocked by a capacitor?
            >
            > The DC ground is connected via the audio ground.
            >
            > > are you suggesting putting this "lowish" value capacitor on all the
            > > USB wires to isolate them to prevent any ground loops?
            >
            > If there is a good ground return to the USB by way of the audio
            cable then
            > this capacitor may not be needed. I leave the USB ground
            disconnected to
            > avoid a ground loop at low frequencies. The 10nF capacitor just
            gives the
            > spiky signal an alternative route.
            >
            > Again I stress that this is just the way I have done it. It seems
            that to
            > get the best results it may be necessary for people to experiment
            until they
            > are satisfied, their conclusions may differ from mine .
            >
            > 73 Alan G4ZFQ
            >
            Ah, the brits and the americans - two peoples separated by a common
            language!
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