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Re: [softrock40] V9 output to audio card?

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  • Alan
    ... From: Ronald Wagner ... One ground connection is needed between the Softrock and the soundcard (computer). Others may find differently but I have always
    Message 1 of 10 , Jan 1, 2009
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      ----- Original Message -----
      From: "Ronald Wagner"


      >I was wondering what everyone thought about having a .1u cap in series with
      > the ground connection of the audio to the sound card. I was thinking that
      > would help eliminate potential ground loop problems.

      One ground connection is needed between the Softrock and the soundcard
      (computer).
      Others may find differently but I have always thought the best results were
      obtained using the ground of the audio cable.
      That means leaving all other grounds between the computer and Softrock
      disconnected.
      In one configuration I had problems with no USB control which I rectified by
      using a capacitor across the USB and Softrock grounds. I took this down to
      500pf but even 0.1uf did not seem to introduce ground loop effects.

      The audio cable and connections need to be good. I have found some cheap
      stereo cables do not have screens. Cutting one figure-of-eight cable I saw
      just two parallel wires.

      Some advocate the use of transformer coupling, I do not think this is
      necessary, but in some circumstances may be desirable.

      73 Alan G4ZFQ
    • Ken
      ... series with ... thinking that ... snip snip ... Alan, does that mean leaving the ground on the USB cable disconnected? HAPPY NEW YEAR!!! 73 de Ken H K9FV
      Message 2 of 10 , Jan 1, 2009
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        > >I was wondering what everyone thought about having a .1u cap in
        series with
        > > the ground connection of the audio to the sound card. I was
        thinking that
        > > would help eliminate potential ground loop problems.

        snip snip

        > 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?

        HAPPY NEW YEAR!!!

        73 de Ken H> K9FV
      • 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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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