Analog audio signals may be structurally divided into Balanced and Unbalanced

The simplest and fastest way to distinguish between the two is to check the connector at the end of the cable.

Examples of connectors using a Balanced signal.- XLR, TRS

Examples of connectors using a Unbalanced signal.- RCA, TS

Balanced cables are cables used at the pro-line level around 4dbu and are mainly used for microphones, recording equipment, or advanced audio.
It consists of three lines and is named Hot (+), Cold (-), and Ground, respectively.

Hot: Normal Signal
Cold: Reverse phase signal
Ground

In general, the cable starts to intervene in the noise from the outside from the moment it is exposed. The longer the cable, the more severe the signal distortion occurs.
The Balanced cable, made to obtain cleaner and stronger sound, consists of three lines: normal signal, reverse phase, and ground.
The side that outputs the signal outputs a normal signal to the hot line and a reverse phase of the normal signal to the cold line.

In the equipment receiving the signal, the cold line is reversed once more.
Imagine what happens if you reverse the cold line that has already been reversed.
The signal flow on the cold line is reversed and converted into a normal signal such as a hot line.
What can be known here is that noise Infused from the outside is also reversed.

The inverted cold line has both a normal signal and inverted noises.
And the current hot line has a normal signal and normal noise.
Finally, the destination equipment combines the hot line and the cold line.
As the two lines are combined, the normal signal is nearly doubled, and the noise is offset by the encounter of normal noise and reverse-phase noise.
In this way, it is possible to obtain a clean signal in which noise is offset and a signal double amplified.
Connectors using a balanced cable include XLR, TRS, etc.
The unbalanced cable consists only of a line through which signals flow and a ground line.
Unbalanced cables are used for instruments with high Impedance that do not require relatively clean signals or for household audio equipment used by ordinary consumer customers.
Connectors used in unbalanced cables include TS, RCA connectors, and the like.

- Ted Kim