Not all power amplifiers are created equal.
In yesterday's post, we touched on the idea of a balanced power amplifier, known to us engineering nerds as a bridged amplifier.
Here's the lowdown.
A balanced power amp operates with two mirror-image signal paths. Instead of just amplifying a signal referenced to ground, it amplifies the difference between two opposing signals. That offers good common mode rejection, which—as we’ve talked about in prior posts—matters most in small signal stages. But at the amplifier output stage, where voltages and currents are high, the advantage of CMR fades.
What does matter is the topology—the design philosophy behind the amp.
As designers, when we choose to build balanced—or more specifically, bridged—power amplifiers, it’s not because they magically sound better. It’s usually a matter of practicality.
Bridged designs allow us to get big wattage output using lower power supply voltages. That means we can use more exotic semiconductors that might not tolerate higher voltages. Sometimes it’s just easier, more cost-effective, or makes better use of available parts. In other words, it's often a smart engineering move—but not necessarily a sonic one.
That said, there’s no golden rule here.
Just like in every corner of high-end audio, great sound isn’t about balanced versus single-ended. It’s about design chops. I’ve heard—and built—some truly stunning single-ended amps. They’re often simpler, more direct, and when designed properly, they can sound breathtaking. On the flip side, I’ve also worked with fully balanced amps that deliver jaw-dropping dynamics, deep black backgrounds, and remarkable clarity (the BHK series of amplifiers are all balanced outputs).
Neither topology has a monopoly on great sound.
But here’s something worth knowing: one of the downsides to bridged amps is how they see speaker loads. A bridged amp views your 4Ω speaker as a 2Ω load. A 2Ω speaker? Now you’re asking the amp to handle 1Ω. That’s tough sledding. It’s not something you, the audiophile, need to worry about directly—but it is something we have to consider carefully as designers.
Next time, we’ll wrap this series up with a wide-angle view of your entire signal chain—and why trusting your ears is still the smartest tool in your audiophile toolbox.
