I've been an advocate of balanced audio connections for many, many years.
Readers of my blog posts no doubt have heard me wax enthusiastically about the virtues of going with XLR cables rather than the (former) consumer audio standard of RCA.
But why? Here's a refresher.
In a small signal chain—say from a DAC to a preamp, or a preamp to a power amp—we’re working with voltages that are often millivolts. Whisper quiet signals, not yet strong enough to punch through noise or interference on their own. That’s where balanced connections shine.
Balanced audio uses three wires: a positive signal, a negative signal (equal in magnitude but opposite in polarity), and a ground. When noise from the environment is introduced—whether it's from a cell phone tower, light dimmer, stereo equipment, or the power cord snaking nearby—it enters both signal wires equally. At the receiving end, a differential amplifier subtracts one signal from the other. That subtraction cancels the common noise.
This magic is called common mode rejection (CMR), and it's a beautiful thing. Like noise-canceling headphones for your stereo system.
Single-ended connections (like RCA cables) don’t get to enjoy this. They carry only one signal and a ground. If EMI or RF sneaks in, there’s no differential amplifier to cancel it. That hum or hash just rides right along into your music. In fact, single-ended cables often act like antennas, happily soaking up whatever interference is in the air.
Which is why I’ll always choose balanced connections when dealing with small signals.
But what happens when the signal gets bigger? Do balanced connections still matter?
That’s where we’ll go next.
