Unbalanced

This is the simplest connection of all and is the sort of thing that you saw in your primary school physics lessons. Get a battery and a light bulb, connect them together with two wires. The electricity is sent up one cable and back down the other and your light turns on. Simple.

Our two wires can carry a varying voltage but the system is still the same, in one end, out the other. This is simple and cheap but if we start introducing unwanted signals (interference) to the cable, then things start getting awkward.

If we turn a mobile phone on or put a big power cable next to our two wires, electromagnetic waves and magnetic fields start to generate electricity in them. You wouldn't notice these fluctuations in a power cable but a microphone cable carries a much weaker signal and so is very susceptible to the interference. Coming out of your speakers is likely to be a really annoying buzzing sound which is a nightmare to find and solve. So is there a better way?

What if we had a way of finding out what unwanted signals have been introduced to our cable? Then we could take it away from our horrible signal and get our original, perfect sound without the buzzing. Well, this is what balanced cables do and the way they do it is by introducing an extra wire into our circuit.

Now as long as our new wire (called a ground) is close to the other two (the positive and negative) then it should be affected in exactly the same way as they are. We can then take the difference between the ground and our signal carrying wires to get a perfect sound.

Balanced connections should always be used with weak signals (eg. microphone outputs) and long cable runs (eg. from band to desk) to lessen the effect of interference and reduce the interference generated. The industry standard balanced connecter is the XLR which is robust and can be locked together to ensure a reliable connection.

XLR wiring