Conductors

• Balanced cabling has three conductors inside its outer jacket: a ground (also known as shield or drain), and one twisted pair of identical conductors. The ground is connected to the cable's outermost conductor, typically a foil wrap that prevents any unwanted noise or interference from reaching the internal twisted pair. The remaining conductors carry the audio signal from a balanced audio output to a balanced audio input.
  
  

Connectors

• Balanced audio cables require specialized connectors for proper functionality. The two most common balanced audio connectors are the tip-ring-sleeve (TRS) 1/4-inch plug and the three-pin XLR connector. Both connectors have two shielded connections for the balanced audio conductors and one connection for the cable's ground conductor. These connectors are also internally grounded, providing a completely shielded connection for the internal audio conductors.
  
  

Noise Rejection

• Balanced audio cables and devices prevent unwanted noise from affecting the intended audio transmission by way of common mode rejection. Each balanced audio output sends its audio into both audio conductors of the cable but in reverse polarity. Each balanced audio input receives the intended audio out of polarity on each conductor. However, each conductor also carries any accidental added noise in correct polarity together. By reversing the polarity of the negative audio conductor, the intended audio is cleanly retained while any noise injected over the cable's run is canceled when the two conductors are mixed.
  
  

Transmission Performance

• Balanced audio lines provide superior audio transmission strength and clarity due to its two-conductor transmission design and common mode rejection scheme. When mixing the two audio conductors at a balanced audio input, any unwanted noise is canceled out, but the intended audio is strengthened by a factor of 3dB. This increase in signal clarity makes possible long audio runs without substantial loss of signal or sound quality.