One of the issues with transferring weak audio signals over wires is that the signals can be affected by any electromagnetic disturbances in the area. The powerful electromagnetic noise generated by overhead electrical cables, a nearby transformer field or even the Earth's own magnetic field can result in annoying distortions of the audio, or crackle, noise or hum in the circuit.
Engineers have found a number of ways to protect the signal from these disturbances, and chief among them is the concept of balanced and unbalanced connectors.
Balanced connectors Balanced connectors constitute a system that allows us to filter out unwanted noise from the useful components of the signal.
The balanced connector system is composed of three wires: The hot and cold wires, which both carry the signal; and a common screen wire. The key to the entire system is that the hot and cold wires carry the same signal, but with the polarity reversed or 'out of phase' - that is, with the peaks and the troughs of the wave reversed, like this:
As the figure shows us, the combination of the out of phase signals, and the fact that noise gets added to both wires equally allows us to output a signal that is twice as strong (2A) as the basic input audio (A), even while we manage to cancel out the noise (n).
Balanced connectors are found on all professional equipment - including semi professional equipment nowadays. For the system to work properly, the origin and receiving systems must both be balanced.
Unbalanced connectors
Unbalanced connectors use a two wire system where the inner (hot) conductor wire is surrounded by an outer wire, which is often in the form of a mesh or shield that is designed to absorb unwanted electrical disturbances. But since the system is not designed for a cancellation process like the balanced system is, the noise cannot be filtered out of the system.
Considerations
Owing to the effectives of the noise canceling system, balanced cables can be as long as 500 metres or more with no loss in the quality of the signal they carry. Unbalanced cables, on the other hand, have to be much shorter to keep the amount of noise they pick up to a moderate level. This is why balanced cables and connections are used in professional equipment, and unbalanced in consumer equipment, since the latter tends to require much shorter lengths of cable.
A Balanced Body & Qi Gong Breathing
Balanced connections are also designed to carry a much higher signal level (usually +4 dBm) than unbalanced connections (usually - 7.8dBm). There are a number of equipment combinations and setups where we are required to connect balanced and unbalanced equipment; and when a balanced
input is connected to unbalanced equipment, we must be careful while amplifying the signal, since it is already at a level much higher than what the unbalanced system was designed for . Conversely, an unbalanced connector connected to a balanced input will actually be feeding it a signal that is too low for what it is designed for.
In such situations, the solution is to use a piece of equipment called a balancing amplifier, that converts balanced inputs to unbalanced and vice versa. The illustrations in this section show a variety of balanced and unbalanced connectors, and how the wires are connected.
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