Balanced vs Single-Ended: What You Actually Gain

A balanced output gives you up to 6.02 dB more voltage, which is four times the power into the same load. That is the entire mechanism. Whether you get all of it depends on the amplifier's current limit, and there is a cost that almost nobody mentions.

The honest version

A balanced output is two amplifiers driving opposite ends of the same driver. One swings positive while the other swings negative, so the voltage across the headphone doubles: +6.02 dB, four times the power. The driver cannot tell where the voltage came from. There is no separate sonic mechanism, no wider soundstage that arrives with the extra wire.

You only get the full four times when the amplifier is voltage-limited. Doubling the voltage also doubles the current demand, so into low-impedance headphones the current ceiling arrives first and the gain collapses. For an ideal 2 V, 100 mA design with zero output impedance the crossover sits at 40Ω, and below it the gain falls away — about +4.1 dB into 32Ω. A real output impedance moves that crossover down and shaves the top off the gain, which is why the calculator above rarely shows a clean +6.02 even into high impedance: set the output impedance to zero and it will.

And the cost: balanced doubles the output impedance, because both amplifier halves contribute their own. Damping factor is halved. For a 300Ω dynamic headphone that is irrelevant; for a multi-driver IEM with a swinging impedance curve it can undo more than the extra power gains you. Check it against the one-eighth rule before assuming balanced is an upgrade.

Two more things worth knowing. Each half of a balanced output does see an effective half-impedance load, which pushes its own distortion up — but published measurements of finished products usually show balanced measuring the same or better, because the signal rises 6 dB while the noise floor does not, so do not expect it to sound worse. And on many products the single-ended jack is derived from one leg of the balanced output, in which case single-ended is about 6 dB down by construction and the balanced figure is the amplifier's real specification rather than a bonus — though not every design is built that way.

Never connect a passive splitter or a balanced-to-single-ended adapter that shorts one leg to ground. On a bridged output both legs are driven, and shorting one can destroy the amplifier.

What the two published figures actually imply

No maker prints “my balanced output is this much stronger than my single-ended one”. They print two power figures, and the difference between them is arithmetic — ours, not theirs. Twice the voltage is four times the power, so the textbook answer is +6.02 dB, and the textbook answer is not what comes out.

124 of the 280 products here carry a separate balanced rating. A row below exists only where both figures — balanced and single-ended — are marked published at the same load, which leaves 104 of them. If one of the pair had been worked out by this site, the “gain” would be the gap between a maker’s number and our own extrapolation, which is no finding at all.

The median of those 104 is +4.04 dB, not +6.02. Only 12 of them reach the textbook figure. 27 give less than three decibels. And 12 give nothing at all or go backwards: their balanced jack is rated at or below their single-ended one.

The largest gain on the list belongs to the FiiO M17 at +7.78 dB from its own figures into 32 Ω — more than the theory allows, which says something about how the two ratings were taken rather than about the circuit. At the other end the SPL Phonitor xe comes out at -5.86 dB, meaning its published balanced power is lower than its published single-ended power.

A figure well under +6.02 dB is not proof of a weak balanced stage. It is just as likely that the two ratings were measured at different distortion limits, or that the single-ended output is fed from the same bridge and already uses most of the available swing. What the column does show is that the published numbers do not support the usual claim: on this evidence, going balanced for six decibels is a coin flip. And six decibels is four times the power but, on the rule this site uses elsewhere that ten decibels sounds roughly twice as loud, well short of twice as loud. What that headroom is actually worth is its own page.

What the makers' own numbers say

124 of the 280 sources in this database publish a separate rating for the balanced output, which makes the claim above checkable rather than a matter of belief. Take every one of those products, compare its two published power figures at the same load, and the theoretical +6.02 dB turns into this:

The pattern is exactly the one the mechanism predicts. Into 600Ω, where an amplifier is limited by how many volts it can swing, the median gain is 5.7 dB — close to the theory. Into 32Ω, where the current ceiling arrives first, the median falls to 4.3 dB. The missing decibels are not a mystery and they are not marketing; they are the current limit, published by the makers themselves and visible the moment you line the two columns up.

3 of them go backwards

Three products in this database publish less power balanced than single-ended into 32Ω: the SPL Phonitor xe at -5.9 dB, the SPL Phonitor x at -1.5 dB, the iFi Zen CAN at -1.2 dB. Balanced is not a bigger number by definition — it is a different output stage, and on some designs it is the weaker one into a low impedance. These are published figures, not measurements: the makers say so themselves, on their own pages, and almost nobody reads that far down the table.

And a few beat the theory

At the other end, 17 of the 124 products here publish more than +6.02 dB into 32Ω — up to 7.8 dB on the FiiO M17. More than four times the power cannot come from bridging two identical halves, so those are not one amplifier wired differently: the balanced side has its own gain, its own rail, or both. That is worth knowing, because it means “balanced” on a spec sheet does not describe one fixed thing.

The cost, in the same makers' figures

74 products publish an output impedance for both jacks. The median balanced figure is 1.65× the single-ended one, and 24 of them are exactly double — which is what two halves in series should give. But 20 publish the same figure for both outputs, which either means the balanced stage was designed around the problem or that nobody re-measured. Either way, the flat “balanced doubles your output impedance” is true more often than not and is not a law.

46 publish a noise figure for both, and there the direction is consistent: the balanced output is noisier on 30 of them, by a median of 1.36×. For a 300Ω dynamic that is nothing. For a sensitive in-ear it can cost you more than the extra power buys. The hiss calculator takes both figures.