Do you know the difference between a balanced line and an unbalanced line? If we're talking about analog audio, this difference between balanced and unbalanced is also the difference between consumer products, which are almost always unbalanced, and professional, which is almost always balanced. To go into the details of these differences would take a number of blogs, so I'm going to try and condense it here.

Balanced lines are a system that puts the audio signal on two wires. You do this by feeding the line and picking up the signal at the other end with an audio transformer. These days you can use a real wound coil of wire transformer or you can use a circuit that mimics that transformer, something called active balancing. The person who really put these active balanced circuits on the map was Greg Mackie while at Tapco, and at the company that followed, Mackie.

The reason that Mackie and many other similar companies can offer you a decent mixer for very little money is active balancing. Compared to a circuit or to a chip or two, real wound transformers are expensive and heavy, especially if their performance is any good. They are hard to make and a really good single wire-wound transformer can cost as much as a whole Mackie mixer. On the other hand, there have been lots of improvements in chip design over the years from folks like T.H.A.T. and their InGenius 1200, or the LMV831 family of chips from National Semiconductor. These chips are getting closer and closer to wire-wound real transformer performance and at a fraction of the cost.

The real secret is that a balanced line will reject electromagnetic noise (EMI, RFI) but allow the audio signal to go through. It will also reject noise from the pairs around it, like in a multi-pair snake cable or even from 50Hz or 60Hz power wiring. You absolutely must use balanced lines, if you are running any audio near lighting or power wiring.