In the last couple of posts, I've explained why a balanced small signal from source to preamp matters. A balanced signal can enjoy the benefits of CMR (common mode rejection) by removing distortion and noise.
But what about a balanced signal to the loudspeaker?
Once a signal leaves the preamp and heads to the power amplifier, things change.
We’re no longer dealing with fragile millivolts. Now we’re talking about volts—lots of them—and current. This is where the signal gets beefy. It's strong, muscular, and ready to move loudspeaker cones back and forth with power.
At this stage, the balanced versus unbalanced debate falls apart.
Let me explain why.
In a loudspeaker with a moving coil architecture (let's say a conventional woofer motor) a balanced connection still offers common mode rejection (CMR), sure. But when we’re pushing, say, 50 volts into a loudspeaker with 10 amps of current, the little gremlins that used to haunt our small signal chain—the EMI, the radio frequency interference, the electrical hum—just don’t matter anymore.
They don't have the power to move the needle. Literally. They can’t make a speaker cone budge.
A tiny bit of noise might sneak into a speaker cable. That’s fine. It’s like a gnat trying to wrestle a bear. The signal is so large that any unwanted noise gets buried, ignored by the sheer momentum of the waveform driving the speaker.
So, balanced is great for small signals but not important for big signals.
When do big signals get balanced and why?
A balanced amplifier output is often referred to as a bridged output, and it’s a fairly common approach in audio design.
In this setup, two power amplifiers are used together to create a single balanced output. Sounds impressive, right? But here’s the thing—it’s not done for sonic reasons. There's no real “balanced benefit” happening at the speaker end. What it does offer is a practical design advantage: more power output using lower internal power supply voltages. That’s great for us engineers, but it doesn’t necessarily translate to a better musical experience for you, the listener.
So while balanced connections are critical for small signals, once we’re into the world of big signals—amplifiers and speakers—they’re more of a nice idea than a necessity. Kind of like wearing a helmet while walking.
Tomorrow we continue.
