Balanced inside

We discovered in yesterday's post how music is differentiated and noise is eliminated in a balanced cable. Are there benefits beyond simple noise reduction possible through the use of common mode rejection? Yes. And that is because the rejection of things in common is not limited to noise. Everything in common is rejected: music. noise, and interestingly enough, distortion. If the two conductors of the cable have the same distortion products on it, those distortions are also eliminated. So, how might we use this to our advantage? By moving the discussion away from balanced interconnects to the circuitry itself. You may have heard the term (as applied to amps, preamps and analog stages of all kinds) balanced amplifier design. Or perhaps it was expressed as a 'fully balanced' or 'true balanced' design. These are all the same things, yet they aren't used in the same way by all manufacturers. Understanding what they mean will help enlighten your decision making process when it comes to purchasing a product. A balanced design means that internally all signals run in balanced mode, from input to output. To handle this, the amplification electronics are essentially doubled: one amplifier for the positive going music and another for the negative traveling musical signals. There are a number of different approaches to accomplish this, but all should have similar results when it comes to lowering distortion products common to both halves of the amplifier chain. Tomorrow let us examine how this works and what the advantages are. I'll also touch on why some manufacturers claim one thing but actually give something else.