Loading ...
Sorry, an error occurred while loading the content.

balancing

Expand Messages
  • Pietro M.P. Sammarco
    hey there, maybe this is dumb question... if I record a balanced signal into two mono inputs, I m recording two 180-out-of-phase signals... and when
    Message 1 of 5 , Oct 18, 2005
    • 0 Attachment
      hey there,
      maybe this is dumb question...
      if I record a "balanced" signal into two mono inputs, I'm recording two
      180-out-of-phase signals... and when listening to them (over monitors) the
      almost completely cancel eachother out (as they should)

      so if I invert one side, am I basically balancing the signal? would it be
      the same as properly recording a balanced signal?

      Or is there more math involved that I'm unaware of..?

      -pietro


      http://geocities.com/pietrosammarco
      http://geocities.com/chubbosound
      http://geocities.com/openepo
      http://theyshoothorses.org
    • KenBobBrewsBeer
      The idea of balancing is to create an out-of-phase version of the original signal and send both down the cable. Noise is picked up euqally and at the same
      Message 2 of 5 , Oct 19, 2005
      • 0 Attachment
        The idea of balancing is to create an out-of-phase version of the
        original signal and send both down the cable. Noise is picked up
        euqally and at the same polarity in both wires. So in one wire you
        have S+N and in the other you have -S+N. At the receiving end, the
        two signals are subtracted, (S+N) - (-S+N) = S-(-S) + (N-N) = 2S +
        0. The signal is restored and the noise cancels.

        Technically then, to "balance" the signals at your monitors, you
        would have to do this subtraction. Inverting one channel
        accomplishes this by adding (acoustically) one channel and the
        negative (inversion) of the other.


        --- In micbuilders@yahoogroups.com, "Pietro M.P. Sammarco"
        <pietro79@h...> wrote:
        >
        > hey there,
        > maybe this is dumb question...
        > if I record a "balanced" signal into two mono inputs, I'm
        recording two
        > 180-out-of-phase signals... and when listening to them (over
        monitors) the
        > almost completely cancel eachother out (as they should)
        >
        > so if I invert one side, am I basically balancing the signal?
        would it be
        > the same as properly recording a balanced signal?
        >
        > Or is there more math involved that I'm unaware of..?
        >
        > -pietro
        >
        >
        > http://geocities.com/pietrosammarco
        > http://geocities.com/chubbosound
        > http://geocities.com/openepo
        > http://theyshoothorses.org
        >
      • Mike Feldman
        ... Actually, the signal does not have to equal and opposite in a balanced connection. Only the impedance that the reciever s differential inputs see needs to
        Message 3 of 5 , Oct 19, 2005
        • 0 Attachment
          KenBobBrewsBeer wrote:

          > The idea of balancing is to create an out-of-phase version of the
          > original signal and send both down the cable. Noise is picked up
          > euqally and at the same polarity in both wires. So in one wire you
          > have S+N and in the other you have -S+N. At the receiving end, the
          > two signals are subtracted, (S+N) - (-S+N) = S-(-S) + (N-N) = 2S +
          > 0. The signal is restored and the noise cancels.

          Actually, the signal does not have to equal and opposite in a
          balanced connection. Only the impedance that the reciever's
          differential inputs see needs to be the same, so that the
          induced noise in the conductors is the same, and N - N = 0.
          S2 and S3 absolute magnitude doesn't matter as long as
          S2 - S3 = S, so S2 - 0 = S2 = S works.

          > Technically then, to "balance" the signals at your monitors, you
          > would have to do this subtraction. Inverting one channel
          > accomplishes this by adding (acoustically) one channel and the
          > negative (inversion) of the other.

          AKA a difference amplifier. But the input impedance needs to be
          the same so that the induced noise currents are the same.
          The closer the match, the more perfectly cancelled the noise.

          In a talk at an AES meeting given by Bill Whitlock of Jensen
          Transformers, he mentioned that all the mic cables he was measuring
          had slightly different capacitanec between each conductor
          and the shield. When he asked the Belden engineers why that was
          so, they said that the dyes to make the insulation different
          colors always gave the insulation different dialectric properties.

          -- Mike
        • Pietro M.P. Sammarco
          so then the answers to my questions if I invert one side, am I basically balancing the signal? would it be the same as properly recording a balanced signal?
          Message 4 of 5 , Oct 20, 2005
          • 0 Attachment
            so then the answers to my questions "if I invert one side, am I basically
            balancing the signal?
            would it be the same as properly recording a balanced signal?" are "yes"?

            >From: "KenBobBrewsBeer" <kenbob@...>
            >Reply-To: micbuilders@yahoogroups.com
            >To: micbuilders@yahoogroups.com
            >Subject: [micbuilders] Re: balancing
            >Date: Wed, 19 Oct 2005 12:38:39 -0000
            >
            >The idea of balancing is to create an out-of-phase version of the
            >original signal and send both down the cable. Noise is picked up
            >euqally and at the same polarity in both wires. So in one wire you
            >have S+N and in the other you have -S+N. At the receiving end, the
            >two signals are subtracted, (S+N) - (-S+N) = S-(-S) + (N-N) = 2S +
            >0. The signal is restored and the noise cancels.
            >
            >Technically then, to "balance" the signals at your monitors, you
            >would have to do this subtraction. Inverting one channel
            >accomplishes this by adding (acoustically) one channel and the
            >negative (inversion) of the other.
            >
            >
            >--- In micbuilders@yahoogroups.com, "Pietro M.P. Sammarco"
            ><pietro79@h...> wrote:
            > >
            > > hey there,
            > > maybe this is dumb question...
            > > if I record a "balanced" signal into two mono inputs, I'm
            >recording two
            > > 180-out-of-phase signals... and when listening to them (over
            >monitors) the
            > > almost completely cancel eachother out (as they should)
            > >
            > > so if I invert one side, am I basically balancing the signal?
            >would it be
            > > the same as properly recording a balanced signal?
            > >
            > > Or is there more math involved that I'm unaware of..?
            > >
            > > -pietro
            > >
            > >
            > > http://geocities.com/pietrosammarco
            > > http://geocities.com/chubbosound
            > > http://geocities.com/openepo
            > > http://theyshoothorses.org
            > >
            >
            >
            >
            >
          • Rich Peet
            Yes, it should work as balanced. You can confirm it by taking your cable and opening the hood of your car and putting the mic cable over the top of the engine.
            Message 5 of 5 , Oct 29, 2005
            • 0 Attachment
              Yes, it should work as balanced. You can confirm it by taking your
              cable and opening the hood of your car and putting the mic cable over
              the top of the engine. Then you can compare one mono input to the
              pair under a high cable inserted noise environ.

              Rich Peet

              --- In micbuilders@yahoogroups.com, "Pietro M.P. Sammarco"
              <pietro79@h...> wrote:
              >
              > hey there,
              > maybe this is dumb question...
              > if I record a "balanced" signal into two mono inputs, I'm recording two
              > 180-out-of-phase signals... and when listening to them (over
              monitors) the
              > almost completely cancel eachother out (as they should)
              >
              > so if I invert one side, am I basically balancing the signal? would
              it be
              > the same as properly recording a balanced signal?
              >
              > Or is there more math involved that I'm unaware of..?
              >
              > -pietro
              >
              >
              > http://geocities.com/pietrosammarco
              > http://geocities.com/chubbosound
              > http://geocities.com/openepo
              > http://theyshoothorses.org
              >
            Your message has been successfully submitted and would be delivered to recipients shortly.