Can someone explain to me why it seems most end game setups are "balanced" setups? Does it actually provide any difference in sound quality? Is it just another way to throw money at the hobby or actually worth it for those wanting to upgrade sound quality?
First you have to understand that there's "balanced" and then theres "balanced." What balanced is understood to mean by the rest of the audio word, particularly the professional side of the audio world, refers to line level interfaces, i.e. from a source component to a preamp or from a preamp to a power amp.
In this instance, what balance refers to is a balance of impedances, specifically between the non-inverting output and ground and the inverting output and ground. These impedances should be the same, hence "balanced." The purpose of this is to be able to reject what's called "common-mode noise." This is noise that is picked up by the cable and is picked up in equal proportions on the non-inverting and inverting lines.
On the input side, the cable drives what is called a "differential input." A differential input only amplifies the difference seen between the non-inverting and inverting lines and rejects anything that is common to both lines, like noise. If the impedances of the outputs and the cable are not balanced, this results in a conversion from common-mode to normal mode, meaning that the noise on one line is not of exactly the same amplitude as the noise on the other. Whatever the difference is, that will be amplified along with the signal.
This is what "balanced" is known to be by the rest of the audio world. And in small setups where you're not dealing with long runs of cable, doesn't really offer any meaningful benefit, other than some people think it's cool because that's what "the pros use." But the pros are dealing with hundreds of feet of cable often in noisy environments.
"Balanced" as used in the headphone world, is what the rest of the audio world calls "bridged." But those who first started making bridged headphone amplifiers didn't know any better and so they used the term "balanced" which has remained ever since and caused no end of confusion.
In a bridged situation, what's typically done is to essentially use two complete amplifiers for each channel. One amplifier is fed a non-inverted signal and the other is fed an inverted signal. When fed from the balanced output of a source component, this is pretty straightforward. But single-ended inputs have to be run through additional circuitry in order to produce an inverted signal to feed to the other amplifier.
The result of this is a greater voltage swing at the output. That's because the difference between +1 volt (the non-inverted signal) and -1 volt (the inverted signal) is 2 volts. The result is double the voltage swing which translates into four times the power into a given load.
Bridging was commonly used in car audio back before they started using DC to DC converters to increase the 12 volt car battery voltage to higher voltages so they could achieve more power. Bridging allowed you to get the most power from the car's 12 volt system.
However bridging has no real benefit in AC powered gear where your power supply voltages can be whatever you want them to be. People often talk about "four times the power" when referring to "balanced" amps, but this is meaningless. Four times the power of what? You can achieve whatever power you want from a single-ended amp. Others talk about "double the slew rate." But this too is meaningless as there are no amplifiers out there slew limiting.
Bridging may be useful in battery powered situations where you have limited voltage available and don't want to resort to using a DC to DC converter, but I see no benefit beyond that.
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