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Thread: Balanced Signal

  1. #1

    Balanced Signal

    As far as I understand...

    Mono -> 2 Wires (1 Signal Wire and 1 Ground Wire)

    Stereo -> 3 Wires (2 Signals [hot+cold] and 1 Ground Wire)

    So I have an Mbox 2 Pro and the outputs are (as stated on the website) Impedance Balanced Monitor Outputs.

    So I could use a Mono on the Left and the Right output or a Stereo cable on each to make it balanced.

    But could I use that same stereo cable to plug into a STEREO output (as the Mbox 2 Pro has an output that is 2 channels of audio (5&6). Does this mean that the stereo cable comes unbalanced as the hot+cold wires are being used for L & R audio rather then L & L or R & R?

    Also the website states that Mbox 2 MINI (which I used to have) has UNBALANCED OUTPUTS... does this mean even if I use a stereo jack that the signal wont be balanced? how come? Is it the interface itself that phase inverts the signals and not the wire so using a stereo wire on a mono port would litterally do nothing?

    Thanks for your help, Jake.

  2. #2
    Senior Member SC358's Avatar
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    Hello Jake,
    Welcome to MC. I found your questions challenging because you got me confused. It has to do with your use of terminology. Your usage of "stereo" and "balanced" signals are being interchanged and I'm getting lost.
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    Quote: ShakeyX
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    Stereo -> 3 Wires (2 Signals [hot+cold] and 1 Ground Wire)
    This is not stereo but a balanced signal. A stereo signal is an application of using 2 or more independent mics and channels to give the listener the sensation of the source is coming from all around them or natural sound.
    Quote
    Quote: ShakeyX
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    But could I use that same stereo cable to plug into a STEREO output (as the Mbox 2 Pro has an output that is 2 channels of audio (5&6). Does this mean that the stereo cable comes unbalanced as the hot+cold wires are being used for L & R audio rather then L & L or R & R?
    Two separate channels usually does imply L & R (or Ch 1 & Ch 2), whether balanced or unbalanced, so your wiring would be L & L, R & R.
    Quote
    Quote: ShakeyX
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    Also the website states that Mbox 2 MINI (which I used to have) has UNBALANCED OUTPUTS... does this mean even if I use a stereo jack that the signal wont be balanced? how come?
    Yes - because the manufacturer has designed it that way basically - I don't know if this answer actually satisfies your question. In addition, the difference is not just circuitry itself, there is a business cost of making an unbalanced or balanced signal.
    Quote
    Quote: ShakeyX
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    Is it the interface itself that phase inverts the signals and not the wire so using a stereo wire on a mono port would litterally do nothing?
    Correct but more like the audio circuit not the interface, unless that is what you meant.

    I hope I was able to figure out, what you were asking. Basically, I substituted stereo for balanced. If I made it worse, please let me know so that I could correct myself.
    Last edited by SC358; 1st Feb 2010 at 19:41.
    SC358
    Relationships are based on compromises - behavior accepted is behavior repeated.

  3. #3
    No this is perfectly fine, what I meant was that something you would name a "STEREO WIRE" could be used either to carry a Stereo signal or a Balanced signal.

    As if you plug a 1/4 TRS jack into a Stereo output is unbalanced (technically as a L & R would have to be sent down the hot and cold wires)

    But plugging a 1/4 TRS into a Balanced Mono output (such as a Monitor Output Left or Right) would make the jack send either 2 lefts or 2 rights down the hot and cold wire which are out of phase with each other.

    Is that right?

    On a side note I would imagine when using an unbalanced stereo connection the L & R would still go through the phase process but as they are different waveforms wouldnt combine and cancel each other out at the end? is this true?

  4. #4
    A balanced output is a single, mono output with two wires plus (usually) ground. The signal appears as a voltage difference across the two wires; at the same instant one wire has a positive voltage on it, the other has an equal negative voltage on it.

    In modern equipment, this is usually created by having two mirror-image IC chips driving the two wires. They are actually two separate, opposite-polarity unbalanced outputs, though that is not how they are intended to be thought of or used.

    The idea behind balanced wiring is that, since the signal is sent and received as a voltage difference across two wires, any voltage that is the same on the two wires - like hum or dimmer buzz - will be rejected.

    With a stereo unbalanced output, you still have two wires, but they are not opposite polarity. One wire carries the left signal and the other carries the right signal. The signal on either wire appears as a voltage measured against the shield, rather than against the other wire.

    A stereo balanced signal would have four wires, two for each channel.

    An unbalanced output cannot be turned into balanced by any kind of plug or cable; no cable generates an additional, opposite-polarity signal. However, a tranformer-based isolation box can turn unbalanced into balanced.

    "Impedance balanced" means that you have two wires per channel, but instead of a real balanced output, the second wire has a resistor to ground that's equal to the impedance of the amp driving the other wire. This is less expensive than a real balanced output, but if the unit you're routing the signal to has a balanced input, you still get most of the interference-rejection goodness. An impedance-balanced output can drive either a balanced or an unbalanced input.

    So, what exactly are you trying to do?

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