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

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  • 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 1 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 2 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 3 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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