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29424Re: V9 output to audio card?

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  • R. R. Robson
    Jan 2, 2009
    • 0 Attachment
      --- 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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