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Balanced Vs. Unbalanced Cables (What’s the Difference?)

What is the difference?

Connection
Creative Commons License photo credit: M Skaffari

An unbalanced audio path has two conductors. One carries the audio signal and the other is the shield/ground. There is nothing at all wrong with an unbalanced signal but at times can be susceptible to picking up interference from radio frequencies or electromagnetic fields that cause noise and buzz.

A balanced signal has three conductors. It relies on a sum and difference principal.
Sum and difference is the combining (summing) of two signals that are out of phase from each other. Whatever doesn’t cancel out is what you’re left with (difference).

When two identical signals of identical amplitude (volume) are combined and one is 180 degrees out of phase from the other you have complete cancellation of that audio. However, if one of those signals is a different amplitude, you don’t get complete cancellation. And it’s this principal that makes a balanced audio path work.

The output from a balanced piece of gear will have the audio signal on pin 2 (hot). That same signal will be present on pin 3 (cold) however that signal is at a lower amplitude than the signal on pin 2. The shield/ground will be on pin 1.

When the signal reaches a balanced input, the signal on pins 2 and 3 are combined with either pin 2 or pin 3 (usually pin 3) out of phase. If that cable happens to pick up interference along the way, it will be on all pins, in phase together and at the same amplitude. When it gets to the input, pins 2 and 3 are combined out of phase and any signal exhibiting the same amplitude (the noise) will cancel out completely. Since the audio is at different amplitudes, it doesn’t cancel out and you’re left with the difference: clean audio!

As for the mics, most all are designed with a balanced output and should be plugged in to the balanced input of a microphone amplifier (pre-amp)
Plugging a mic into an unbalanced input won’t ruin anything but mics generate a very low level signal that needs lots of gain to bring it up in level. Amplifying a signal that much benefits from the noise canceling of a balanced connection.

For more info on cables and connections visit Tweakheadz: All About Cables

  • Thank you for making this clear!

    My lecturer taught us about this, but didn’t state anything about the cold/hot signal being higher in amplitude from the other. That got me really confused since that would completely cancel any sound. Not anything ‘noise-reduction’ if you ask me…

    I appreciate your effort on this complex yet simple topic.

    Cheers from South-Africa!

    Kelvin

    June 4, 2012

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