We’re going deeper today into the world of audio cables, like a pearl diver testing her limits. Let’s see if I can keep this entertaining!
Continuing our series on symptoms of a serious audio system, today’s subject is the use of balanced audio cables in a system. These will typically show up between a preamplifier or home theater processor and a power amplifier. Nicer (read: more expensive) preamplifiers, network streamers and CD players will have balanced outputs, which should be an indication that this is a better method.
Now when I say balanced, I don’t mean that the sound character of the cables is subjectively or objectively balanced. I’m talking about balanced in a scientific sense, and it’s something that the professional recording audio world has known about and insisted upon using for years.
Music is made up of waves. A basic wave that you can hear is represented as a squiggly line on a graph or machine. What you’re looking at with the squiggly graph is that wave played out over time. There is a trough, where the wave dips low and then heads upward, and a tip, where the wave peaks and starts heading down again.
Music is a massive bunch of these squiggles all thrown in together, but it can be represented for our purposes as a single squiggle line. Now picture this squiggle line, and let’s mentally cut it in half horizontally. The upper half is just the tips of the wave, and the lower half is just the troughs. Because of the time element and the way the wave is shaped, the tips never line up vertically with the troughs.
Balanced cables, also known as XLR cables by the typical connectors used at the ends, take advantage of this fact to pull off something special: “common mode noise rejection.”
Picture sound-canceling headphones for a moment. I’ve written several times over the years about how these work. They use microphones to listen to surrounding noise, and they inject that noise into your music, delayed half a wave. So they change a tip into a trough, and the tips and troughs of the surrounding noise align vertically.
When this happens, sound cancels out. That’s why they’re called noise-canceling headphones instead of noise-reducing headphones — they really do nix that business right out.
Balanced XLR cables in your audio system do the same thing for any stray electrical noise or electro-magnetic noise or radio frequency interference. Balanced cables split your music in half, sending the tips to one wire and the troughs to another. A third wire carries the return path, which is known as the “ground.” If any of that nasty stuff gets into your music via the cable (a common occurrence at varying levels), it will show up in both the tips wire and the troughs wire at the same exact moment.
Now think about this. If a tip and a trough of the same wave are aligned at the same time, they cancel out. So that means anything that enters both wires of the cable that is not music (remember that music will never have identical tips and troughs aligned at the exact same time), will be both a tip and trough of the same wave at the same time, and will cancel out.
Take a tip from the pro audio world: Go balanced!