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Re: [softrock40] Re: V9 output to audio card?

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  • Alan
    ... From: Ken ... That is the way I do it, I use a 10nF capacitor from the USB ground to the Softrock ground. I m not saying it s the best way but it works
    Message 1 of 10 , Jan 1, 2009
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      ----- Original Message -----
      From: "Ken" >
      >> One ground connection is needed between the Softrock and the
      >>soundcard computer). That means leaving all other grounds between the
      >>computer and Softrock disconnected.
      >
      > Alan, does that mean leaving the ground on the USB cable disconnected?
      >

      That is the way I do it, I use a 10nF capacitor from the USB ground to the
      Softrock ground.
      I'm not saying it's the best way but it works for me.

      73 Alan G4ZFQ
    • Ken
      OK, I see that would isolate and prevent any DC ground loops, but can the ground loop not be in the AC region? OR maybe it s only the DC ground loops that
      Message 2 of 10 , Jan 1, 2009
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        OK, I see that would isolate and prevent any DC ground loops, but can
        the ground loop not be in the AC region? OR maybe it's only the DC
        ground loops that give a problem?

        Thanks to all for the education.

        73 de Ken H> K9FV

        --- In softrock40@yahoogroups.com, "Alan" <g4zfq@...> wrote:
        >
        >
        > ----- Original Message -----
        > From: "Ken" >
        > >> One ground connection is needed between the Softrock and the
        > >>soundcard computer). That means leaving all other grounds
        between the
        > >>computer and Softrock disconnected.
        > >
        > > Alan, does that mean leaving the ground on the USB cable
        disconnected?
        > >
        >
        > That is the way I do it, I use a 10nF capacitor from the USB ground
        to the
        > Softrock ground.
        > I'm not saying it's the best way but it works for me.
        >
        > 73 Alan G4ZFQ
        >
      • Alan
        ... From: Ken ... Well, the current through ground loops is basically at mains frequency and its lower harmonics. A lowish value capacitor will have a
        Message 3 of 10 , Jan 1, 2009
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          ----- Original Message -----
          From: "Ken"

          > OK, I see that would isolate and prevent any DC ground loops, but can
          > the ground loop not be in the AC region? OR maybe it's only the DC
          > ground loops that give a problem?
          >

          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
        • 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 4 of 10 , Jan 1, 2009
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            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 5 of 10 , Jan 2, 2009
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              ----- 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 6 of 10 , Jan 2, 2009
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                > > 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 7 of 10 , Jan 2, 2009
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                  --- 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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