"What's the difference between unbalanced and balanced cables? When do I use balanced and vice versa?"
I'd like to expand a bit on my response to him and answer both of these questions. Let's start by looking at the difference between these 2 types of cables.
I will simplify things just a bit so if you'd like a more in-depth explanation, there is a great post on the Gearslutz forum here.
What's the difference between balanced vs unbalanced cables?
A typical unbalanced cable (like a 1/4 instrument cable) has 2 conductors. The 1st conduction is the audio signal itself and the 2nd is a ground and often a shielding. The main difference comparing balanced vs unbalanced cables is a balanced cable has 1 additional conductor.
The balanced cable will have 1 hot, 1 cold, and a ground/shielding conductor. The signal from both the hot and cold wire is combined, each out of phase with the other. The resulting signal is thus "balanced".
When should I use a balanced cable?
If your connections both in an out are balanced, always try to use a balanced cable. The result will be less chance for interface from outside sources causing unwanted buzzes, static, and hums.
If you're running longer distances a balanced cable is also the preferred option as the signal will be stronger than unbalanced. This means a higher signal to noise ratio. In other words, your audio will be cleaner.
When should I use an unbalanced cable?
Unbalanced cables certainly still have a great value as well. You will need to use an unbalanced cable when your connections don't support balanced. Also many instruments (like guitars) have outputs that only support unbalanced signals. Sometimes you don't have a balanced cable so an unbalanced is your only option.
How do I know if my cable is balanced or not?
Remember that a balanced cable has 1 additional conduct than its unbalanced counterpart. The most popular type of balanced cable is a typical microphone or XLR. Balanced cables can also be 1/4" as well. They are often refereed to as TRS or tip, ring, sleeve. In the image below, all the cables on the left are balanced. The single cable on the right is a typical unbalanced 1/4" cable.
Please feel free to add your comments or questions to the section below.