Modern headphone amps, even shit amps does use bridged output by default due to low supply voltage. By doing so you actually make a even more simple circuit. Basically they marketed out a physical deficiency ie lack of voltage and solution for it as a premium feature.

Does a low Z headphone out need a balanced out due to signal integrity, RF immunity... absolutely no it doesn't work like that, false information, if this DAC is hooked to another power amplifier stage with a XLR, then okay, have your fun, I hope it can drive it without going into oscillation without load.

Does it need a bridge, differential setup? It depends. If the headphones are extremely low Z, hard to drive, maybe. For 99.99% users out there - definitely not, and me included as I use high Z headphones and don't bother myself.

The bridged mode may induce higher THD, due to the fact the amp sees half of the load and and each half contributes their own share of it, so on the paper it would actually look worse.

The older balanced XLR exist for convenience not some audiophile mojo. PA people like to be smart and lazy, they can hook up their gear anywhere, and do their job that they are paid off. You need to have a monitor at the end of that out and you plug it there... if not you can hook it to another device and everything works fine.

TheLostSwedeBalanced audio connector. Most of us normal people wouldn't buy headphones that has that kind of a connector.

So it seems that this DAC is not for ordinary people.

Adrian AndrzejewskiSo it seems that this DAC is not for ordinary people.

Well, I guess it depends on how much you can afford to spend on a pair of suitable headphones.
Most people use 3.5 or 6.35 mm jack headphones.

Let me try to correct some of the confusion/misinfo in this thread and add my 2 cents:

"Balanced headphone" is a misnomer, but it's an established term among headphone audiophiles.

mashieHow would you even use a balanced signal to a pair of headphones unless they have their own built in amplification?

Headphone drivers (which I will just call speakers) are two-terminal devices.
In single-ended amplification one terminal is connected to the amp's output, the other one to the amp's ground. Since ground is the same, multiple speakers can be connected sharing a single ground cable.

Balanced interconnection uses 3 conductors per channel: two signal and one shield (sometimes incorrectly connected to signal ground). The receiver "sees" the difference between the two signal conductors. Note: it does not matter if you have 10V-9V, 0.5V-(-0.5V) or 1V-0V. Balanced does not refer to differential signalling but the balanced impedances between those conductors.
That's why "balanced headphone" is a misnomer.
But you can connect the speaker with the two signal wires. The shield will stay unconnected. This is used in bridged amplification.

I guess that since balanced audio interconnection uses XLR connectors and "balanced headphones" started out using XLR connectors as well, audiophiles probably thought it's all the same..

MusselsI've got plenty of TRS and TRRS cables and headphones here, i also never knew TRRS had the optional 4.4mm connector

It doesn't.
Nippon DICS invented the "Pentaconn" which is a 4.4mm TRRRS (not TRRS!) connector with ... you guessed it ... 5 pins.
It's still a very niche connector, resellers ask ridiculous prices for them, but you can get them relatively cheap from Aliexpress.

VSGHere are the usual three cable connectors on the source side that are used for earphones/IEMs these days (2.5 mm TRRS balanced, 3.5 mm TRS single-ended, 4.4 mm TRRS balanced):

TRRRS, not TRRS.
Pentaconn is special in that it does have a (shared) ground: L+, L-, R+, R-, G.
This ground allows to build very simple adapters to conventional 3-pin stereo jacks by using L+, R+, G.
When going to 2.5mm "balanced" (another misnomer), the ground will not be connected: L+, L-, R+, R-.

Nobody should be surprised that such utterly simple adapters/cables are sold at exorbitant prices to audiophiles.

mashieNo it is just a connection as you would have to a regular speaker instead of sharing ground between two of them. If it was differential you would need extra electronics in the headphones.

To do differential you need three prongs which is why TRS can be used for mono balanced signals, for stereo balanced you would need five.

You don't need extra electronics for a differential signal. It's identical to bridged amplification in this case: 2 signal wires connected to a 2-terminal speaker.
The speaker only "sees" the voltage difference between the two, so it cannot even distinguish between the different kinds of amplification.

Bridged speaker amplification uses differential signalling. That's also what "balanced" (bridged) headphone amps do.

Ferrum MasterModern headphone amps, even shit amps does use bridged output by default due to low supply voltage. By doing so you actually make a even more simple circuit. Basically they marketed out a physical deficiency ie lack of voltage and solution for it as a premium feature.

Yes, this is a "trick" that is used in this device to add 6 dB of voltage gain. The 5V USB supply voltage is inverted which increases the output voltage from 2 Vrms (between any signal conductor and ground) to 4 Vrms (between L+ and L- or R+ and R-).

This however is not done because it's cheap but because it is more efficient than the alternatives and allows the device to produce lots of power despite the limited USB supply voltage.
This is actually important for such dongles because they're intended to be used with smartphones.

Ferrum MasterDoes a low Z headphone out need a balanced out due to signal integrity, RF immunity... absolutely no it doesn't work like that, false information, if this DAC is hooked to another power amplifier stage with a XLR, then okay, have your fun, I hope it can drive it without going into oscillation without load.

Yeah, in proper balanced audio you get noise immunity from the balanced impedances and due to the fact that the 3rd conductor - the shield - is connected to the source's and receiver's chassis.